Chapter VIII: Hemiptera, or Bugs—anoplura 532 (22)

Parthenogenesis seems to be frequent amongst Thysanoptera, {531}and is found in concurrence with diversity as to winged and wingless females of the same species, so as to have given rise to the idea that the phenomena in this respect are parallel with those that are more widely known as occurring in Aphidae. Under certain circumstances few or no males are produced (one of the circumstances, according to Jordan, being season of the year), and the females continue the species parthenogenetically. In other cases, though males are produced they are in very small numbers. Some species of Thysanoptera are never winged; in others the individuals are winged or wingless according to sex. But there are other cases in which the female is usually wingless, and is exceptionally winged. The winged specimens in this case are, it is thought, of special use in disseminating the species. Jordan has suggested that these phenomena may be of a regular nature, but Uzel does not take this view. Another condition may be mentioned, in which the species is usually wingless, but winged individuals of the male as well as of the female sex occasionally appear. _Thrips lini_ apparently makes regular migrations, feeding at one time underground on the roots of flax, and then changing to a life in the open air on other plants.

Numerous forms of Thysanoptera, belonging to both of the great divisions of the Order, have been found fossil in Europe and North America, but all are confined to deposits of the Tertiary epoch.

Of the 135 species known to Uzel, 117 are European; they are divided into two Sub-Orders. 1, Terebrantia, in which the females are provided with an external toothed ovipositor, of two valves; 2, Tubulifera, in which there is no ovipositor, and the extremity of the body is tubular in both sexes. The British species are about 50 in number, and were described by Haliday about 60 years ago;[461] of late they have been very little studied.

The name Physopoda or Physapoda is used for this Order, instead of Thysanoptera, by several naturalists.

{532}CHAPTER VIII

HEMIPTERA—OR BUGS

ORDER IX. HEMIPTERA.

_Mouth consisting of a proboscis or mobile beak (usually concealed by
being bent under the body), appearing as a transversly-jointed rod or
grooved sheath, in which are enclosed long slender setae (like
horse-hairs). Wings (nearly always) four; the anterior frequently more
horny than the posterior pair, and folding flat on the back, their apical
portions usually more membranous than the base_ (Heteroptera); _or the
four wings may cover the abdomen in a roof-like manner, and those of the
anterior pair may not have the basal and apical parts of different
consistences_ (Homoptera); _sometimes all four of the wings are
transparent. The young resembles the adult in general form; the wings are
developed outside the body, by growth, at the moults, of the sides of the
hinder portions of the meso- and meta-notum; the metanotal prolongations
being more or less concealed by the mesonotal._

The Hemiptera or Bugs are perhaps more widely known as Rhynchota. In deciding whether an Insect belongs to this Order the student will do well to examine in the first place the beak, treating the wings as subordinate in importance, their condition being much more variable than that of the beak. The above definition includes no reference to the degraded Anoplura or Lice. These are separately dealt with on p. 599; they are absolutely wingless, and have an unjointed proboscis not placed beneath the body, the greater part of it being usually withdrawn inside the body of the Insect.

The Hemiptera are without exception sucking Insects, and {533}the mouth-organs of the individual are of one form throughout its life. In this latter fact, coupled with another, that the young are not definitely different in form from the adult, Bugs differ widely from all other Insects with sucking-mouth. They agree with the Orthoptera in the facts that the mouth does not change its structure during the individual life, and that the development of the individual is gradual, its form, as a rule, changing but little. In respect of the structure of the mouth, Orthoptera and Hemiptera are the most different of all the Orders. Hence, Hemiptera is really the most isolated of all the Orders of Insects. We shall subsequently see that, like Orthoptera, the Order appeared in the Palaeozoic epoch. Although a very extensive Order, Hemiptera have for some incomprehensible reason never been favourite objects of study. Sixty years ago Dufour pointed out that they were the most neglected of all the great Orders of Insects, and this is still true; our acquaintance with their life-histories and morphology especially being very limited.

There is probably no Order of Insects that is so directly connected with the welfare of the human race as the Hemiptera; indeed, if anything were to exterminate the enemies of Hemiptera, we ourselves should probably be starved in the course of a few months. The operations of Hemiptera, however, to a large extent escape observation, as their mouth-setae make merely pricks that do not attract notice in plants; hence, it is probable that {534}injuries really due to Hemiptera are frequently attributed to other causes.

In the course of the following brief sketch of the anatomy and development of Hemiptera, we shall frequently have to use the terms Heteroptera and Homoptera; we may therefore here mention that there are two great divisions of Hemiptera having but little connection, and known by the above names: the members of these two Sub-Orders may in most cases be distinguished by the condition of the wings, as mentioned in the definition at the commencement of this chapter.

EXTERNAL STRUCTURE.—The mouth-parts consist of an anterior or upper and a posterior or lower enwrapping part, and of the organs proper, which are four hair-like bodies, dilated at their bases and resting on a complex chitinous framework. The lower part forms by far the larger portion of the sheath and is of very diverse lengths, and from one to four-jointed: it is as it were an enwrapping organ, and a groove may be seen running along it, in addition to the evident cross-segmentation. The upper covering part is much smaller, and only fills a gap at the base of the sheath; it can readily be lifted so as to disclose the setae; these latter organs are fine, flexible, closely connected, rods, four in number, though often seeming to be only three, owing to the intimate union of the components of one of the two pairs; at their base the setae become broader, and are closely connected with some of the loops of the chitinous framework that is contained within the head. Sometimes the setae are much longer than the sheath; they are capable of protrusion. Although varying considerably in minor points, such as the lengths of the sheath and setae, and the number of cross-joints of the sheath, these structures are so far as is known constant throughout the Order. There are no palpi, and the only additions exceptionally present are a pair of small plates that in certain forms (aquatic family Belostomidae) lie on the front of the proboscis near the tip, overlapping, in fact, the last of the cross-articulations.

Simple as is this system of trophi its morphology is uncertain, and has given rise to much difference of interpretation. It may be granted that the two portions of the sheath are respectively upper lip, and labium; but as to the other parts wide difference of opinion still prevails. On the whole the view most generally accepted, to the effect that the inner pair of the setae correspond {535}in a broad sense with maxillae of mandibulate Insects, and the outer pair with mandibles, is probably correct. Mecznikow, who studied the embryology,[462] supports this view for Heteroptera, but he says (_t.c._ p. 462), that in Homoptera the parts of the embryo corresponding with rudimentary maxillae and mandibles disappear, and that the setae are subsequently produced from peculiar special bodies that are at first of a retort-shaped form; the neck of the retort becoming afterwards more elongate to form the seta; also that in the Heteropterous genus _Gerris_ the embryology in general resembles that of Homoptera, but the development of the setae is like that of other Heteroptera (_t.c._ p. 478). This discontinuity in the development of the Homopterous mouth has since been refuted by Witlaczil,[463] who found that the retort-shaped bodies really arise from the primary segmental appendages after they have sunk into the head. We are therefore justified in concluding that the mouth-parts are at first similarly developed in all Hemiptera, and that this development is of a very peculiar nature.

Smith is convinced that there are no traces of mandibular structure in any Hemiptera.[464] On the other hand, numerous entomologists have supposed they could homologise satisfactorily various parts of the Hemipterous trophi with special parts of the {536}maxillae and labium of mandibulate Insects. This point has recently been discussed by Marlatt[465] and by Heymons.[466] From the latter we gather that the mode of growth is peculiar by the extension backwards of some of the sclerites, and their becoming confounded with parts of the wall of the head. From all this it appears that at present we cannot correctly go farther than saying that the trophi of Hemiptera are the appendages of three head-segments, like those of other Insects. The views of Savigny, Léon,[467] and others to the effect that labial palpi, and even other parts of the labium of Mandibulata can be satisfactorily identified are not confirmed by Heymons.

Underneath the pharynx, in the head, there is a peculiar structure for which we have as yet no English term. It was apparently discovered by Landois and Paul Mayer,[468] and has been called "Wanzenspritze," which we translate as syringe. It may be briefly described as a chamber, into which the salivary ducts open, prolonged in front to the neighbourhood of the grooves of the setae in the rostrum; behind, it is connected with muscles; it has no direct connection with the pharynx, and though it was formerly supposed to be an organ of suction, it seems more probable that it is of the nature of a force-pump, to propel the products of some of the bug's glands towards the tips of the setae.

The rostrum being extended from its position of repose, the tip of the sheath is brought into contact with the object to be pierced, the surface of which is probably examined by means of sensitive hairs at the extremity of the sheath; these therefore functionally replace to some extent the palpi of other Insects. As a rule the sheath does not penetrate (though there is reason for believing that in various of the animal-feeding bugs it does so), but the setae are brought into action for piercing the skin of the plant; they are extremely sharp, and the outer pair are usually barbed, so that when once introduced a hold is easily maintained. This being established it is thought that the salivary pump comes into play, and that a fluid is injected into the object pierced so as to give rise to irritation or congestion, and thus keep up a supply of fluid at the point operated on: this fluid extends along the grooved setae by capillary attraction, and the {537}rapidity of the current is increased by a pumping action of the pharynx, and possibly by movements of the setae themselves. Though the setae are often extremely elongate—sometimes several times the length of the body—they are nearly always slender, and there is no reason to suppose that a perfect, or air-tight, tube is formed; hence it is probable that capillary attraction is really the chief agent in the ingestion of the fluid. The slight diversity of structure of the Hemipterous trophi is in very striking contrast with what we find in mandibulate Insects, and in the less purely suctorial Insects, such as Diptera and some divisions of Hymenoptera. Schiödte in commenting on this has suggested that it is probably due to the small variety of actions the rostrum is put to.[469]

The head exhibits great variety of form; in the Homoptera the front part is deflexed and inflexed, so that it is placed on the under surface, and its anterior margin is directed backwards; it is often peculiarly inflated; in the Lantern-flies or Fulgoridae (Fig. 282) to an incomprehensible extent. In the great Water-bugs, Belostomidae, there is on the under surface a deep pocket for each antenna, beautifully adapted to the shape of the curiously-formed appendage (Fig. 279). The prothorax is always very distinct, frequently large, and in many of the Heteroptera (Fig. 257), as well as in the Homopterous family, Membracidae (Fig. 283), assumes the most extraordinary shapes. Both meso- and meta-thorax are well developed. The former is remarkable for the great size of the scutellum; in some cases (Plataspides, Scutellerides) this forms a large process, {538}that entirely covers and conceals the alar organs, so that the Insect has all the appearance of being apterous. The exact composition of the abdomen has not been satisfactorily determined, opinions varying as to whether the segments are nine, ten, or eleven in number. The difficulty of determining the point is due to two facts: viz. the extreme modification of the terminal segments in connection with the genital appendages, and the prominence of the extremity of the alimentary canal. If this terminal projection is to be treated as a segment, it would appear that eleven segments exist, at any rate in some cases; as the writer has counted ten distinct segments in a young Coreid bug, in addition to the terminal tube. This tube in some of the male Heteroptera is very subject to curious modifications, and has been called the rectal cauda. Verhoeff considers that ten segments were invariably present in the females examined by him in various families of Heteroptera and Homoptera.[470] In Aphidae (a division of Homoptera), Balbiani considers there are eleven abdominal segments present; but he treats as a segment a projection, called the cauda, situate over the anus; this structure does not appear to be homologous with the rectal cauda we have just mentioned. In Coccidae the number of abdominal segments is apparently reduced. Schiödte states[471] that the older authorities are correct in respect of the stigmata; there are, he says, in Heteroptera invariably ten pairs; one for each thoracic segment; and seven abdominal, placed on the ventral face of the pleural fold of the abdomen. In some cases there are additional orifices on the external surface that have been taken for stigmata, though they are really orifices of odoriferous glands; these openings may exist on the metasterna or on the dorsal surface of the abdomen. The lateral margins of the abdomen are frequently greatly developed in Heteroptera, and are called "connexivum;" the upper and lower surfaces of the body meeting together far within the marginal outline. Dr Anton Dohrn many years ago[472] called attention to the extremely remarkable structure of the terminal segments in many male Hemiptera; and the subject has been subsequently very imperfectly treated by the present writer and other entomologists, but it has never received the attention it deserves.

{539}In the females of numerous Heteroptera and Homoptera (Capsidae, Cicadidae, etc.) there is a well-developed ovipositor, that serves both as a cutting instrument to make slits in the stems of plants, and as a director to introduce the eggs therein. Verhoeff considers that it always consists of two pairs of processes (though one pair may be very small), one from the eighth abdominal segment, the other from the ninth.[473]

The antennae usually have very few joints, often as few as four or five, their maximum number of about twenty-five being attained in the males of some Coccidae, this condition being, however, present in but few of even this family. In _Belostoma_ (Fig. 279) they assume extremely curious forms, analogous to what we find in the Coleopterous genus _Hydrophilus_. In addition to the compound eyes, there are usually ocelli, either two or three in number, but wanting in many cases. The usual number of joints of the tarsi is three, but in Coccidae there is only one joint.

The wings (Fig. 258) exhibit much diversity. The anterior pair usually differ greatly from the posterior; they are called elytra, hemi-elytra or tegmina. This difference in the two pairs is the rule in the first of the great divisions of the Order, and the name Heteroptera is derived from the fact. In this Sub-Order the front wings close over the back, and are more or less horny, the apical part being, however, membranous. Systematists make use of the wings for the purpose of classification in Heteroptera, and distinguish the following parts, "clavus," "corium," "membrane," the corium being the larger horny division, the clavus the part lying next the scutellum and frequently very sharply distinguished from the corium; the membrane is the apical part. The outer or costal part of the wing is also often sharply delimited, and is called the "embolium;" in the great family Capsidae and a few others, the outer apical part of the {540}corium is differentiated from the rest of the surface, and is termed the "cuneus." In Plataspides, one of the divisions in which the alar organs are entirely covered by the scutellum, they are modified in a very remarkable manner. In the Homoptera the divisions named above do not exist, and the wings in repose are placed in a different position, as stated in our definition of the Order. It is said to be very difficult to homologise the wing-nervures of Hemiptera, and nothing appears to be known as to the mode of their development.

The alar organs in Hemiptera exhibit a very frequent form of variation within the limits of the same species; this has not yet been elucidated.[474] In some cases in the Heteroptera nearly all the individuals of a generation may have the wings aborted; sometimes this occurs as a local variation. In Aphidae the occurrence of winged and wingless individuals is very common, and has even become an important factor in their extraordinary life cycles. (See _Chermes_, etc., subsequently.)

INTERNAL ANATOMY.—The alimentary canal presents considerable diversity and some remarkable features. There is a slender tube-like oesophagus and a large crop. It is difficult to assign any of the parts posterior to this to the divisions usual in other Insects, and it is said that the distinction of parts histologically is as vague as it is anatomically. In the Heteroptera the Malpighian tubes open into two (or one) vesicular dilatations seated immediately in front of the short rectum: between this point and the crop there may be a very elongate, slender portion with one or more dilatations, these parts apparently replacing the true or chylific stomach. There is no gizzard. In the Homoptera the relations of the divisions of the alimentary canal are even more puzzling; the canal is elongated and forms coils, and these are connected with tissues and tunics so as to make their dissection extremely difficult. List says that there are great differences in the alimentary canal among the members of the one family Coccidae. There are usually four Malpighian tubes, but in Coccidae there is only one pair, and in Aphidae none. The excretory cells of these tubes are in Hemiptera of remarkably large size. There is a large development of salivary glands, at least two pairs existing. There can be little doubt that some of their products are used for purposes of injection, as {541}already described, though Künckel came to the conclusion that the saliva when placed in living plants is totally innocuous.[475]

The ganglia of the nervous system are all concentrated in the thorax and head. In some cases (in various Homoptera) the infra-oesophageal ganglion is placed at a distance from the supra-oesophageal ganglion, and may even be united with the thoracic mass of ganglia (_Orthezia_, etc.); in this case the chitinous framework of the mouth-parts is interposed between the supra- and the infra-oesophageal ganglia. In _Pentatoma_ all the three ganglionic masses are brought into close proximity, but in _Nepa_ the thoracic mass of ganglia and the infra-oesophageal ganglion are widely separated.

The ovarian tubes vary greatly in number: according to List in _Orthezia cataphracta_ the number differs considerably in different individuals, and even in the two ovaries of the same individual, the number being usually two. The testes are not placed in a common tunic, though they are frequently approximated or even contiguous.[476]

The smell of bugs is notorious. In many species it is not unpleasant, though as a rule it is decidedly offensive. It is a remarkable fact that the structures connected with the production of this odour are different in many cases in the young and in the adult. The odour emitted by the latter proceeds from a sac seated at the base of the abdomen, and opening exteriorly by means of an orifice on each side of the metasternum; while in the young there are two glands situated more dorsally and a little more backwards, and opening on two of the dorsal plates of the abdomen (Fig. 255, A).[477] In the young the dorsum of the abdomen, where the stink-glands open, is exposed, but this part in the adult is covered by the wings. The odorific apparatus is specially characteristic of Heteroptera, and Künckel states that there is so much variety that generic and even specific characters might be drawn from conditions of the stink-glands. As a rule they are most constantly present in the plant-feeding forms; in some essentially carnivorous forms (Reduviidae, Nepidae, {542}Notonectidae) they are entirely absent. The offensive matter emitted by _Notonecta_ is of a different nature, and is probably anal in origin.

METAMORPHOSIS OR POSTEMBRYONIC DEVELOPMENT.—In the language of the systematists of metamorphosis, Hemiptera are said to be Homomorpha Paurometabola—that is, the young differ but little from the adult. According to Brauer's generalisations they are Menorhynchous, Oligonephrous, Pterygogenea, _i.e._ they have a sucking mouth that does not change during life, few Malpighian tubes, and are winged in the adult state. It is generally admitted that the Homoptera do not completely agree with Heteroptera in respect of the metamorphosis, it being more marked in the former, and in Coccidae attaining (as we shall mention when discussing that family) nearly if not quite the condition of complete metamorphosis of a peculiar kind. Unfortunately we are in almost complete ignorance as to the details of the life-histories and development of Heteroptera, so that we can form no generalised opinion as to what the post-embryonic development really is in them, but there are grounds for supposing that considerable changes take place, and that these are chiefly concentrated on the last ecdysis. The young of some bugs bear but little resemblance to the adult; the magnificently-coloured species of _Eusthenes_ (Fig. 255), before they attain the adult condition are flat, colourless objects, almost as thin as a playing-card; it is well known that the extraordinary structures that cover and conceal the body in Plataspides, Scutellerides, Membracides, etc., are developed almost entirely at the last moult: it is not so well known that some of these changes occur with much rapidity. A very interesting account of the processes of colour-change, as occurring in _Poecilocapsus lineatus_ at the last ecdysis, has been given by Lintner,[478] and from this it appears that the characteristic coloration of the imago is entirely developed in the course of about two hours, forming a parallel in this respect with Odonata. When we come to deal with Aphidae we shall describe the most complex examples of cycles of generations that exist in the whole of the animal kingdom.

FOSSIL HEMIPTERA.—Hemiptera are believed to have existed in the Palaeozoic epoch, but the fossils are not numerous, and opinions differ concerning them. _Eugereon hockingi_, a {543}Permian fossil, was formerly supposed to be a Homopterous Insect, but it is very anomalous, and its claim to a position in Hemiptera is denied by Brauer,[479] who considers it to be Orthopterous. It is now generally recognised that this fossil requires complete reconsideration. Another Permian fossil, _Fulgorina_, is admitted to be Homopterous by Scudder, Brauer and Brongniart. Scudder thinks the Carboniferous _Phthanocoris_ was an Archaic Heteropterous Insect, and if correct this would demonstrate that both of the two great Sub-Orders of Hemiptera existed in Palaeozoic times. Brauer, however, is inclined to refer this fossil to Homoptera, and Brongniart[480] speaks of it as being without doubt a Fulgorid. _Dictyocicada_, _Rhipidioptera_ and _Meganostoma_, from the Carboniferous shales of Commentry, have also been referred to Fulgoridae by Brongniart, but the evidence of their alliance with this group is far from satisfactory. In the Secondary epoch numerous Hemiptera existed, and are referred to several of the existing families. They come chiefly from the Oolite. In the Eocene of the Isle of Wight a fossil has been discovered that is referred to the existing Homopterous genus _Triecphora_.

We are not entitled to conclude more from these facts than that Homoptera probably appeared before Heteroptera, and date back as far as the Carboniferous epoch.

CLASSIFICATION AND FAMILIES.—No complete catalogue of Hemiptera exists, but one by M. Severin is in course of publication. It is probable that there are about 18,000 species at present described, two-thirds of this number being Heteroptera. In Britain we have about 430 species of Heteroptera and 600 of Homoptera. The classification of the Order is not in a very advanced condition. The following table exhibits the views of Schiödte[481] in a modified form:—

Front of head not touching the coxae. I. Heteroptera.
Front of head much inflexed so as to be in contact with the coxae.
II. Homoptera.

Sub-Order I. Heteroptera.

Posterior coxae nearly globose, partly embedded in cavities, and having
a rotatory movement. Mostly terrestrial forms. 1. Trochalopoda.

Posterior coxae not globose, larger, and not embedded; their articulation
with sternum almost hinge-like. Posterior aspect of hind femur usually
more or less modified for the reception of the tibia when closed on{544}
it: mostly aquatic forms. 2. Pagiopoda.

Division 1. Trochalopoda.

This division includes the majority of the families of Heteroptera—viz.
the whole of the terrestrial families except Saldidae, and it also
includes Nepidae, a family of water-bugs.

Division 2. Pagiopoda.

This includes the six purely aquatic families of Heteroptera, except
Nepidae, which appear to have very little connection with the other
aquatic bugs. The only terrestrial Insects included in the family are the
Saldidae; in these the femora are not modified as they are in the aquatic
forms. Hemiptera that live on the surface of water, not in the water, are
classed with the terrestrial species. With these exceptions this
arrangement agrees with that of GYMNOCERATA and CRYPTOCERATA as usually
adopted,[482] and therefore followed in the following pages. Schiödte's
characters, moreover, do not divide his two divisions at all sharply.

Sub-Order II. Homoptera.

Tarsi usually three-jointed Series Trimera.
" " two-jointed " Dimera.
" " of one joint " Monomera.

The classification of Homoptera is in a most unsatisfactory state;[483]
no two authors are agreed as to the families to be adopted in the series
Trimera. We have recognised only five—viz. Cicadidae, Fulgoridae,
Membracidae, Cercopidae, and Jassidae. The Dimera consists of Psyllidae,
Aphidae, Aleurodidae; and the Monomera of Coccidae only. It is usual to
associate the Dimera and Monomera together under the name of either
Phytophthires or Sternorhyncha, but no satisfactory definition can be
given of these larger groups, though it seems probable that the families
of which they are composed are natural and distinct.

Sub-Order I. HETEROPTERA.

SERIES 1. GYMNOCERATA.

The majority of the terrestrial families of Heteroptera form the series Gymnocerata, in which the antennae are conspicuous, and can be moved about freely in front of the head, while in {545}Cryptocerata they are hidden. The series Gymnocerata includes all the terrestrial Heteroptera, and the two families, Hebridae and Hydrometridae, which live on the surface of the water or in very damp places; while Cryptocerata includes all the forms that live under water.

FAM. 1. PENTATOMIDAE.—_Scutellum very large, at least half as long as the abdomen, often covering the whole of the after-body and alar appendages. Antennae often five-jointed. Proboscis-sheath four-jointed. Ocelli two. Each tarsal claw with an appendage._—This, the largest and most important family of the Heteroptera, includes upwards of 4000 species, and an immense variety of forms. It is divided into no less than fourteen sub-families. The species of one of these, Plataspides, are remarkable for their short, broad forms, and the peculiar condition of the alar organs, which are so completely concealed by the great scutellum that it is difficult to believe the Insects are not entirely apterous. The head is usually inconspicuous though broad, but in a few forms it is armed with horns. Though this sub-family includes upwards of 200 species, and is very widely distributed in the Old World, it has no representatives in America. The Scutellerides also have the body covered by the scutellum, but their organs of flight are less peculiar than they are in the Plataspides; the Insects of this sub-family are highly remarkable on account of their varied and frequently vivid coloration; some of them are metallic, and the colour of their integuments differs greatly in some cases, according to whether the specimen is wet or dry; hence the appearance after death is often very different from that of the living specimen. These Insects are extremely numerous in species. The sub-family Phloeides (Fig. 259), on the contrary, includes only three or four South American species: they have no resemblance at all to other Pentatomidae; they are flat, about an inch long, and look like scales of bark, in this respect agreeing with _Ledra_ and some other Homoptera. The South American sub-family Cyrtocorides (Fig. 260) is of {546}equally small extent; the species are of strange irregular shapes, for which we can find no reason. The Tessaratomides includes many of the largest Hemiptera-Heteroptera, some of its members attaining two inches in length.

The great family Pentatomidae, containing about 400 species, is represented in Britain by about 36 native species, the most interesting of which are perhaps those of the genus _Acanthosoma_. De Geer noticed long ago that the female of _A. griseum_ exhibits great solicitude for its young, and his statement has since been confirmed by Mr. Parfitt and the Rev. J. Hellins, who found that the mother not only protects the eggs but also the young, and that for a considerable time after hatching.[484]

Very little is known as to the life-histories of Pentatomidae. In some cases the young are very different in appearance from the adults. The peculiar great scutellum is not developed till the mature condition is reached. But little attention has been given to the habits of Pentatomidae; it is generally considered that they draw their nutriment from plants; the American _Euthyrhynchus floridanus_ has, however, been noticed to suck the honey-bee, and we think it probable that a good many Pentatomids will be found to attack Insects.

The term Pentatomidae as applied to this family is of modern origin: in most books the equivalent group is called Scutata, or Scutati, and the term Pentatomidae is restricted in these works to the sub-family called Pentatomides in the system we adopt.

FAM. 2. COREIDAE.—_Scutellum not reaching to the middle of the body; proboscis-sheath four-jointed; ocelli present; antennae generally elongate and four-jointed, inserted on the upper parts of the sides of the head; femora not knobbed at the tip._—The members of this great family are easily recognised by the above characters; formerly it was called Supericornia in connection with the characteristic position of the antennae. About 1500 species are known, and they are arranged in no less than twenty-nine sub-families. Many of them are Insects of large size, and they frequently have a conspicuous disc, or dilatation, on one of the joints of the antennae.

{547}

Fig. 262—_Phyllomorpha laciniata_, carrying some of its eggs. Spain.]

Another very curious and, as yet, inexplicable peculiarity very commonly met with among them, is that the hind legs may be of great size and deformed; either the femora or the tibiae, or both, being very much distorted or armed with projections. Brilliant colour is here comparatively rare, the general tone being indefinite tints of browns, greys, or smoky colours. The South American genus _Holymenia_ (_Copius_ of older authors) consists of slender forms, having the elytra transparent even on the basal part like Homoptera; this and some other peculiarities give the species of this genus a certain resemblance to Insects of other Orders; Westwood says that _Diateina holymenoides_ (Diptera) greatly resembles a bug of the genus _Holymenia_. The tropical American genus _Diactor_ consists of a few species of elegant colour having the hind legs very peculiarly shaped, the tibiae being flattened and expanded in a sail-like manner, and ornamented with agreeable colours different {548}from those on the rest of the body; they are made more conspicuous by the femora being remarkably long and thin; it is probable that they are used as ornaments. The subfamily Phyllomorphides consists of about a dozen species, and is found in several of the western parts of the Eastern hemisphere, one species, _P. laciniata_, occurring in Southern Europe. This Insect is of very delicate texture, and the sides of the body are directed upwards and deeply divided so that a sort of basin is formed, of which the dorsum of the body is the floor; the Insect is very spinose, and is thus enabled to carry its eggs, the spines helping to retain them in position on the back. It is said to be the male that thus carries the eggs. This species is able to stridulate, and when doing so vibrates its antennae with excessive rapidity. We have only about a score of species of Coreidae in Britain, and none of the remarkable forms of the family are among them.

FAM. 3. BERYTIDAE.—_Very slender Insects with the first joint of the antennae and the femora thickened at the tips._—This small family was not distinguished from Coreidae by the older authors. It consists of about fifty species, eight of which are found in Britain.

FAM. 4. LYGAEIDAE.—_The characters are the same as those mentioned for Coreidae, except as regards the insertion of the antennae; the upper surface or face of the head is not so flat, but is transversely convex, so that seen in profile the antennae appear to be inserted well down on the sides of the head._—The name Infericornia was formerly applied to these Insects. They are on the average of smaller size than the members of the Coreidae or Pentatomidae, and are much less conspicuous in colour and form; a good many of the larger Lygaeids are, however, variegate with black, yellow, and red. The family is very numerous in species, about 1400 being known; they are arranged in thirteen sub-families; we have about sixty species in Britain, nearly all small. _Eremocoris_ lives, when immature, in the nests of the wood-ant, according to Wasmann. The family includes some notorious Insect-pests. The Chinch-bug, _Blissus leucopterus_, commits very serious ravages on corn and grasses in North America. The Cotton-stainer, _Dysdercus suturellus_ is also very injurious to cotton in certain parts of the New World: its growth has been described by Riley,[485] who thinks a dye valuable for {549}commercial purposes might be procured from the Insect. This bug has recently developed the habit of sucking oranges, and has thus become injurious in Florida, as the fruit readily decays after it has been punctured by these Insects. The phenomenon of "micropterism" is exhibited by numerous Lygaeids, as well as by Pyrrhocoridae.

FAM. 5. PYRRHOCORIDAE.—_Distinguished from Lygaeidae only by the absence of ocelli_, and not recognised as a distinct family by all Hemipterists. About 300 species are included. Our only British member is the notorious _Pyrrhocoris apterus_; it is, however, very rare in this country, though it abounds on the Continent, and has been the object of investigation by embryologists and others. It displays in a most marked manner the curious dimorphism as to the alar organs that is so common in certain divisions of Hemiptera; the elytra and wings being sometimes normally developed, while in other cases the wings are entirely absent, and the horny, basal part of the elytra only is present. In some localities, and in some years, only the micropterous form is found, while on other occasions there may be a large percentage of the macropterous form. The abundance of this Insect has enabled the French chemist Physalix to obtain an amount of its colouring matter sufficient for analysis; as the result he procured a substance, insoluble in water, very closely allied to carotine.[486] The Oriental Insect _Lohita grandis_ is one of the most remarkable of Bugs, the male of the Sumatran variety being over two inches in length, having enormously long antennae, and the abdomen extended to about twice the normal length, while the other sex is in the usual condition in these respects. The species is said to be injurious to the cotton-plant in India.

FAM. 6. TINGIDAE.—_Tarsi two-jointed. Elytra more or less reticulate, consisting of strong, irregular, thick lines forming a framework of cells, the enclosed part of the cell being of different texture and frequently transparent; antennae with terminal joint more or less knob-like, the preceding joint very long; ocelli wanting; pronotum prolonged behind, covering the scutellum; front coxae placed at the lack of the thorax._—This is the first of a series of families with only two joints to the feet. These little bugs are very remarkable objects, and exhibit much variety in their peculiar {550}sculpture, which in numerous forms attains a condition of elegance well worthy of attention. There are nearly 300 species known, and in Britain we have about a score. The characters we have given above do not apply to the genus _Piesma_, though it is usually placed in this family; its scutellum is not covered, and ocelli are present. Although but little is known as to the nature of the lives of Tingidae, yet it was pointed out long ago by Réaumur that a species of the family (probably _C. clavicorne_, Fig. 263), lives in deformations of the flowers of the Labiate plant now called _Teucrium chamaedrys_; Frauenfeld has more recently confirmed this observation, and shown that the closely allied _C. teucrii_ affects the flowers of _T. montanum_ in a similar manner.[487]

FAM. 7. ARADIDAE.—_Very flat, broad; scutellum exposed, large or moderate; abdomen broader than the alar organs, which it frequently encases like a broad frame. Front coxae placed in the middle of the prosternum._—These very flat Insects, of obscure colour, have frequently very peculiar sculpture. They live under bark, or on fungi growing from bark, and are supposed to draw their nutriment from the fungi, though but little is actually known as to their natural history. The family is almost cosmopolitan, and includes about 300 species, of which five occur in England. The small sub-family Isoderminae consists of a few species that are placed only provisionally in Aradidae; they differ from the normal members by there being no groove on the {551}breast, so that the rostrum is free. Of the five species, three occur in Chili and Patagonia, two in Tasmania, and one in Australia.

FAM. 8. HEBRIDAE.—_Minute bugs, of semiaquatic habits, clothed beneath with a dense, minute, silvery pubescence; antennae five-jointed; legs of not more than average length; elytra in larger part membranous._—This small family consists altogether of only about a dozen species; we have two species of the genus _Hebrus_ in Britain; they are usually found in very wet moss.

FAM. 9. HYDROMETRIDAE.—_Form very diverse; antennae four-jointed, tarsi two-jointed. Coxae usually widely separated. Either wingless or with elytra of one texture throughout, having no membranous part. Under surface with a minute velvet-like pubescence. In many forms the legs are of great length._—Although of comparatively small extent—scarcely 200 species being at present known—this family is of great interest from the habit possessed by its members of living on the surface of water. In the case of the notorious genus _Halobates_ (Fig. 265) the Insects can even successfully defy the terrors of Neptune and live on the ocean many hundreds of miles from land. There is great variety of form among Hydrometridae. The European and British genus _Mesovelia_ is of short form, and but little dissimilar from ordinary land-bugs, with which, indeed, it is connected by means of the genus _Hebrus_, already noticed. _Mesovelia_ represents the sub-family Mesoveliides, which, though consisting of only four species, occurs in both hemispheres, and in the tropics as well as in the temperate regions. Our species, _M. furcata_, walks on the surface of the water, the movements of its legs and the position of its coxae being those of land-bugs. Another British Insect—the highly remarkable _Hydrometra stagnorum_—is of excessively slender form, with long thin legs, by aid of which it {552}walks on the surface-film of water, above which its body is held well separated. It is easily drowned, and if submerged it has great difficulty in escaping from the water. This genus represents the sub-family Hydrometrides, and is apparently almost cosmopolitan. _Velia currens_ is another common British Insect; it loves the eddies and currents of backwaters on burns and streams, and is very abundant in Scotland. An American ally, _Rhagovelia plumbea_, appears to be not uncommon on the surface of the ocean in the Gulf of Mexico, near the shores. The great majority of the family belong to the division Gerrides, of which the curious, long Insects that float so lazily and skim so easily on the surface of quiet streams are typical. The species of the genus now called _Gerris_, but formerly known as _Hydrometra_ are apparently distributed all over the world; we have ten in Britain. They have very long legs, and on being alarmed move away with the greatest ease.

The genus _Halobates_ includes at present fifteen species. They are found on the ocean, where the surface-water is warm, in various parts of the world. They are destitute of any trace of alar organs, the meso- and meta-thorax are closely united and large, while the abdomen is very small, so that the body is of oval form; the middle legs are thrown so far back that they are placed immediately over the posterior pair. When the sea is calm these Insects skim over the surface with rapidity, but disappear as soon as it becomes agitated. They are believed to feed on small animals recently deceased; Witlaczil says on the juices of jelly-fish. The young are frequently met with, and there can be no doubt that the whole life-cycle may be passed through by the Insect far away from land. The Italian ship _Vettor Pisani_ met with a bird's feather floating on the ocean off the Galapagos Islands, covered with eggs which proved to be those of _Halobates_ in an advanced stage of development. It was formerly believed that the female carries the eggs for some time after their exclusion, and although this has since been denied, it is nevertheless an undoubted fact, for it was observed by Mr. J. J. Walker,[488] to whom we are indebted for a specimen having the eggs still attached to the body, as shown in Fig. 265. Mr. Walker believes the bugs shelter themselves when the sea is at all rough by keeping at a sufficient distance {553}below the surface; they can dive with facility, and are gregarious. They are frequently found close to the shore, and Mr. Walker has even met with them on land. The stink-glands of other Hemiptera are said by Nassonoff to be replaced in _Halobates_ by peculiar ventral glands. An allied genus, _Halobatodes_, was supposed to be oceanic, but this is not the case, some of the species having been found recently in fresh water in India, and others in estuaries at Port Darwin. A remarkable allied form, _Hermatobates haddoni_, was recently discovered by Professor Haddon in Torres Straits. Apart from the oceanic life, _Halobates_ is by no means the most extraordinary of the Hydrometridae. The Javanese _Ptilomera laticaudata_ repeats some of its peculiarities, and is of larger size, with the sexes very different. The most remarkable of the family is perhaps the fresh-water genus _Rheumatobates_ (Fig. 266), in which the males have peculiar prehensile antennae that look like legs. These curious Insects inhabit North America and the West Indies.

We may here notice an enigmatic Insect called _Hemidiptera haeckeli_ by Léon. From the single specimen known it is concluded that the Insect has only one pair of wings, and that they are attached to the metathorax. It is, however, possible, as {554}suggested by Bergroth,[489] that the anterior pair have been detached by some accident.

FAM. 10. HENICOCEPHALIDAE.—_Head swollen behind the eyes so as to form a sort of globe, on the anterior part of which the ocelli are placed. Rostrum extremely short. Elytra rather large, of one consistence throughout; conspicuously veined._—There is only one genus; it is very widely distributed, about a dozen species being known; one of these occurs in the south of Europe. These curious little bugs appear to be most nearly allied to the Reduviidae. According to Westwood and others they are somewhat gregarious; a Tasmanian species dances in the air after the fashion of midges or May-flies, and dispenses an agreeable, musk-like odour.

FAM. 11. PHYMATIDAE.—_Front legs of peculiar structure, short and stout, with long coxae, short thick femora, and tibiae curvate, pointed; frequently without tarsi._—The Insects of this family are believed to be predaceous, the structure of the legs being such as is called raptorial, and one species, _Phymata erosa_, being known to capture and suck honey-bees in North America. There are only about seventy species of Phymatidae known. We have {555}none in Britain, though there are a few in Southern Europe; one of these, _P. crassipes_, extends as far north as Paris. The distinction of the family from Reduviidae is doubtful.[490] There are a few very rare forms (Fig. 267) in which the front tibia is articulated to the femur in such a way that a pair of pincers is formed: the tarsus is in this form, as well as in some other Phymatidae, absent.

FAM. 12. REDUVIIDAE.—_Head more or less elongate, very movable, eyes placed much in front of the thorax, ocelli, when present, behind the eyes. Proboscis short, or moderately short, not extending on to the breast, in repose curved under the head so as to form a loop therewith. Elytra, when present, consisting of three divisions. Tarsi three-jointed._—This is one of the largest and most important families of Hemiptera. Upwards of 2000 species are already known; the habits seem to be chiefly of a predaceous nature, the creatures drawing their nutriment from the animal rather than from the vegetable kingdom, and their chief prey being in all probability other kinds of Insects. There is, perhaps, no family of Insects exhibiting a greater variety of form and colour. The Emesids are amongst the most delicate of Insects, equalling in this respect the {556}daddy-long-leg flies; they are, however, highly predaceous; their front legs are peculiarly formed for capturing and holding their prey, and have long coxae, like _Mantis_, so that these Insects are commonly mistaken for small or young Mantises, from which their sucking proboscis at once distinguishes them. This curious starved-looking form of bug reaches its maximum of peculiarity in the South American genus _Ghilianella_ (Fig. 268). According to Pascoe the linear form enables the young larva to be carried about by the mother, the long slender abdomen of the larva being curled around the thorax of the parent. _Ploiaria pallida_, from Woodlark Island, is an Insect of excessive fragility and elegance, with the long thin legs coloured with alternate patches of black on a white ground, giving rise to a very curious appearance remarkably analogous to what we find in some of the equally delicate daddy-long-leg flies.

We have three species of Emesides in Britain, but most of our Reduviidae belong to the sub-family Nabides. These approximate to ordinary bugs in appearance and characters more than do any other of the Reduviidae. One of our indigenous Nabides is of great interest from the curious resemblance it has to an ant (Fig. 269). The likeness is brought about by the sides of the base of the abdomen being very pallid in colour, except a dark mark in the middle; this mark is in shape like the pedicel of an ant. Viewed in profile it is found that on the base of the abdomen there is an elevation like the "scale" in this position in {557}ants, and that the abdomen is extremely ant-like in form. This resemblance is quite parallel with that of an Orthopteron to an ant (see Vol. V. p. 323); the Insect is by no means uncommon, and it is strange that this curious case of resemblance should hitherto have escaped notice. The bug runs about on plants and flowers, and is frequently in company with ants, but we do not know whether it preys on them. Not the least remarkable of the facts connected with this Insect is that the resemblance is confined to the earlier instars; the adult bug not being like an ant. We may here mention that there are numerous bugs that closely resemble ants, and that on the whole there is reason to believe that the resembling forms are actually associated during life, though we really know very little as to this last point.

The little sub-family Holoptilides, with twenty-five species, but widely distributed in the Eastern hemisphere, is remarkable on account of the feathered {558}antennae and legs of its members (Fig. 270). Altogether fourteen sub-families are recognised, the most extensive one being Harpactorides, including a great variety of remarkable forms; in the South American genus _Notocyrtus_ (better known as _Saccoderes_, Fig. 257), the prothorax is swollen and covers the body to a greater or less extent in the fashion of a hood. In _Yolinus_ and _Eulyes_ the coloration is the most conspicuous system that could be devised, the sides of the abdomen (connexivum) being expanded into bright-red lobes on which are placed patches of polished-black. The most remarkable form of Reduviid is, perhaps, one from China (Fig. 271) of considerable size, of great fragility, and greatly resembling, like some Emesides, a daddy-long-legs fly, though it does not belong to the Emesides. It is an altogether anomalous form. According to Seitz there is found on the Corcovado in Brazil a Reduviid that exactly resembles one of the dark stinging-wasps of the genus _Pepsis_, and the bug makes the same sort of movements as the wasp does, though these are of a kind quite different from those of ordinary bugs.[491]

Although the attacks of Reduviidae on animals are usually confined to the smaller and more defenceless kinds, yet this is by no means invariably the case; there are in fact numerous species that do not hesitate to attack man himself. Several species of _Reduvius_ do this in Southern Europe, and are frequently met with in houses. _R. personatus_ is the only species of the genus in England; though far from common anywhere, it is sometimes found in houses, and is said to destroy the common bed-bug; it is able to pass its whole existence in our habitations, for the young are found as frequently as the adult, and are usually concealed by a quantity of dusty matter, or refuse, adhering to the body. This habit of covering the body with some foreign substance is natural to the Insect, the young that are found on trees being covered with matter derived therefrom. Darwin has given us an account of {559}the Benchucha,[492] a bug an inch long, which in South America attacks human beings after the fashion of the common bed-bug. In this case no ill-effects follow the attack, but in the case of _Conorhinus sanguisuga_ in Arizona, great pain and inflammation ensue and may end in the gathering and discharge of pus.

Not the least remarkable of characters of _Reduviidae_ is the form of the eggs of some of the species (Fig. 272, and Vol. V. Fig. 78, C); the egg bearing a peculiar operculum, the purpose of which is at present quite mysterious.

FAM. 13. AËPOPHILIDAE.—A single species forms this family. It is of considerable interest, as it is incapable of flight, passing a large part of its life covered by the sea. _Aëpophilus bonnairei is a small Insect with quite short head, without ocelli, and with the organs of flight represented by a pair of very short elytra, with rounded hind-margins._ It is found on the shores of Western France, and, as a great rarity, on our own south coast. It no doubt sucks small soft animals. In the Channel Islands it occurs in spots where it is nearly always covered by a considerable depth of water.

FAM. 14. CERATOCOMBIDAE.—_Minute bugs with ocelli and elytra. Rostrum free. Head not broad, somewhat prolonged in front; eyes close to the thorax. Elytra usually without a distinctly separated membrane. Tarsi three-jointed._—This family includes at present only a few, minute, fragile bugs, that have often been classified with Cimicidae or Anthocoridae. We have only two British species, one of which, _Dipsocoris alienus_, is common amongst the damp shingle at the margins of the burns and waters of Scotland.