Chapter VIII: Hemiptera, or Bugs—anoplura 532 (5)

SUB-FAM. 1. MUTILLIDES.—_The sides of the pronotum reach the tegulae: the
female is destitute of wings and ocelli, frequently having the parts of
the thorax so closely soldered that the divisions between them are
obliterated: the males are winged, furnished with ocelli, and having the
thoracic divisions distinct; intermediate tibiae with two apical spurs.
Front wing with two or three sub-marginal cells. The larvae live
parasitically at the expense of other Hymenoptera Aculeata._

The Mutillides have some resemblance to ants, though, as they are usually covered with hair, and there is never any node at the base of the abdomen, they are readily distinguished from the Formicidae. The great difference between the sexes is their most striking character. Their system of coloration is often very remarkable, the velvet-like pubescence clothing their bodies being variegated with patches of sharply contrasted vivid colour; in other cases the contrast of colour is due to bare, ivory-like spaces. They have the faculty of stridulating, the position and nature of the organ for the purpose being the same as in ants.

Very little exact information exists as to the habits and life-histories of the species. Christ and Drewsen, forty or fifty years ago, recorded that _M. europaea_ lives in the nests of bees of the genus _Bombus_, and Hoffer has since made some observations on the natural history of the same species in South East Europe, where this _Mutilla_ is found in the nests of ten or eleven species of _Bombus_, being most abundant in those of _B. agrorum_ and _B. variabilis_; occasionally more individuals of _Mutilla_ than of bees may be found in a nest. He supposes that the egg of the _Mutilla_ is placed in the young larva of the _Bombus_, and hatches in about three days; the larva feeds inside the bee-larva, and when growth is completed a cocoon is spun in the interior of the pupa-case of the bee. When the perfect Insects emerge, the males leave the nest very speedily, but the females remain for some time feeding on the bees' honey. Females are usually produced in greater numbers than males. This account leaves {95}much to be desired. From the observations of Radoszkowsky it is clear that other species of Mutillides are by no means confined to the nests of _Bombus_ but live at the expense of Aculeate Hymenoptera of various groups. This naturalist asserts that the basal abdominal segment of the parasite resembles in form that of the species on which it preys.

The apterous condition of the females of Mutillides and Thynnides is very anomalous in the Fossors; this sex being in the other families distinguished for activity and intelligence. The difference between the sexes is also highly remarkable. The males differ from the females by the possession of wings and by the structural characters we have mentioned, and also in a most striking manner in both colour and form; Burmeister, indeed, says that in South America—the metropolis of Mutillides—there is not a single species in which the males and females are alike in appearance; this difference becomes in some cases so extreme that the two sexes of one species have been described as Insects of different families.

Upwards of one thousand species are assigned to the genus _Mutilla_, which is distributed over the larger part of the world; there is so much difference in these species as to the nervuration of the wings in the males, that several genera would be formed for them were it not that no corresponding distinctions can be detected in the females. Three or four species of _Mutilla_ are described as being apterous in the male as well as in the female sex; they are very rare, and little is known about them. Only three species of Mutillides occur in Britain, and they are but rarely seen, except by those who are acquainted with their {96}habits. The African and East Indian genus, _Apterogyna_, includes some extremely peculiar Hymenoptera; the males have the wing nervuration very much reduced, and the females are very ant-like owing to the deep constriction behind the first abdominal ring.

SUB-FAM. 2. THYNNIDES.—_Males and females very different in form; the
male winged, the front wing with three, or only two, sub-marginal cells;
the female wingless and with the thorax divided into three sub-equal
parts._

The Thynnides are by some entomologists not separated from the Mutillides; but the distinction in the structure of the thorax of the females is very striking. In the Thynnides the nervuration of the wing appears always to extend to the outer margin, and in the Mutillides not to do so. This family is represented in Britain by a single very rare Insect, _Methoca ichneumonides_: to the unskilled observer the female would appear to be without doubt an ant. This Insect is by some considered as the type of a family distinct from the Thynnides proper. Thynnides are numerous in Australia. Very little is really known as to their habits, though it has been stated that they are parasitic on Lepidoptera, Bakewell having obtained specimens from subterranean cocoons of that Order. Those who are interested in differences between the sexes of one species should examine the extraordinary examples of that phenomenon presented by the Thynnides; the dissimilarity throughout the group—which is now of considerable extent—being so extreme that no entomologist would from simple inspection believe the two sexes to have any connection; but the fact that they are so connected has been demonstrated beyond doubt. In very few {97}cases, however, have the sexes been matched, so that at present males are no doubt standing in the lists of Hymenoptera as one species and their females as other species.

SUB-FAM. 3. SCOLIIDES.—_Pronotum reaching back to the tegulae; legs
stout; intermediate tibiae with one apical spur; both sexes winged; the
nervures not extending to the posterior_ (i.e. _distal_) _margin_.

This group includes some of the largest and most powerful of the Aculeate Hymenoptera. Its members are usually hairy Insects with thick legs, the colour being black, more or less variegated with bands or spots of red or yellow; the hind body is elongate, has only a very short pedicel, and in the male is usually terminated by three projecting spines. The pronotum is of variable dimensions, but its front angles are always co-adapted with the points of insertion of the front wings. The nervuration of the front wings is confined to the basal part, the extensive apical or outer area possessing no nervures. There is frequently a great difference in the size of the two sexes of the same species, the female being very much larger than the other sex. The larvae, so far as is known, devour those of Lamellicorn Coleoptera.

Fabre has investigated the habits of some of the species of Scoliides found in France, and has informed us that their means of subsistence consists of larvae of the larger Lamellicorn beetles, _Cetonia_, _Oryctes_, _Anoxia_, and _Euchlora_; these beetles belong to very different divisions of the Lamellicornia, but they have in common the fact that their larvae are of subterranean habits, living in the earth or in accumulations of débris in which there is a large proportion of vegetable matter or roots. The female _Scolia_ penetrates into the ground in order to find the Lamellicorn larvae necessary as food for its progeny. _Scolia bifasciata_ {98}attacks the larvae of several species of _Cetonia_, and _S._ (_Colpa_) _interrupta_ chooses the larvae of the chafers _Anoxia villosa_ and _A. matutinalis_. The mother _Scolia_ enters the ground in August or September, and having found a suitable larva stings it and deposits an egg on the ventral surface of the prey; the paralysed larva is left where it was found, no attempt being made to place it in a special receptacle. The egg is placed on the ventral surface, well behind the feet, under a mass of matter in the alimentary canal. Shortly after being hatched the young destroyer penetrates with its head the skin of the victim, and in this position commences to feed; it is necessary that it should obtain its food without killing the _Cetonia_ larva, for it cannot prosper on decaying food, so that if the _Cetonia_ larva die the _Scolia_ larva likewise perishes; the latter, accordingly, does not withdraw its head from the interior of the victim, but remains always in the same position, as it grows larger extending its head forwards into the front part of the interior of its victim; the internal organs of the latter are consumed in a systematic order so as to delay bringing about its death till the last moment, and thus all the interior of the _Cetonia_ larva is appropriated till nothing remains but an empty skin. By a series of experiments, Fabre showed how essential it is that this apparently revolting operation should be carried on with all details strictly _en règle_. If the head of the _Scolia_ larva be taken out from the victim and applied to another part of the body of the _Cetonia_, the result is that it cannot eat; even if it be replaced in the original situation, after being taken away, it frequently happens that the _Cetonia_ larva dies, its death involving also that of the destroyer. It is necessary, too, that the victim should be paralysed, for if an intact _Cetonia_ larva be taken and bound down in such a position that it cannot move, and if a small orifice in its skin be made in the proper spot and a young _Scolia_ larva be placed on it, the little parasite will avail itself of the opportunity and commence to feed on the larva provided for it, but the latter will speedily die, and the _Scolia_ necessarily perishes with it. Thus both the paralysis of the victim and the special mode of eating are essential to the life of the _Scolia_. The operation of stinging the larva so as to produce the necessary paralysis, or rather insensibility, is a difficult one, and requires great skill and patience. The _Cetonia_ larva is of large size, and must be pierced in one particular spot; {99}in order to reach this the _Scolia_ mounts on its victim, and is frequently dislodged by its struggles; sooner or later, however, the proper position is obtained by the wasp, and the larva is then stung in the exact spot necessary to allow the sting (and the poison introduced by it) to reach the most important of the nervous ganglia that control the movements of the body, this spot being, in the case of the _Cetonia_, the line of demarcation between the pro- and meso-thorax, on the middle line of the ventral surface of the body. The _Scolia_ gives but one sting to the victim, and this it will not administer until it can do so exactly in the proper place. This practice of devouring the victim slowly, without killing it till all is eaten, is very widely spread in the Hymenoptera, and it is satisfactory to find that we may infer from Fabre's observations that it is not so horrible as it would at first appear; for it is probable that the stinging prevents decomposition of the victim, not by reason, as some have supposed, of the poison injected by the wasp having an antiseptic effect, but rather by means of destroying sensibility, so that the creature does not die from the pain, as it is believed it did in certain cases where Fabre induced the young _Scolia_ larva to feed on a victim that had not been stung. We may here remark that very little exact information exists as to the operation of stinging. Fabre attaches great importance to the sting being inflicted on a nerve-ganglion. Whether a sting that did not reach this part might not have a sufficient effect appears, however, doubtful.[46]

A remarkable form of Scoliides, with wings of smaller size than usual and deeply divided, has been described by Saunders under the name _Pseudomeria graeca_. Still more remarkable is _Komarovia victoriosa_ found in Central Asia; in this Insect the male retains the appearance of a slender, pallid _Scolia_, but the female differs totally in form, and has the peculiar wings so reduced in size as to be useless for flight.

SUB-FAM. 4. SAPYGIDES.—_Closely allied to the Scoliides, but possessing
slender legs and antennae; also the first abdominal segment is less
disconnected from the second, so that the outline {100}is less
interrupted; the eyes are deeply emarginate; the hind body is not spinose
at the apex._

The economy of _Sapyga_, the only genus, has been the subject of difference of opinion. The views of Latreille and others that these species are parasitic upon bees is confirmed by the observations of Fabre, from which it appears that _S. 5-punctata_ lives in the burrows of species of the bee-genus _Osmia_, consuming the store of provisions, consisting of honey-paste, that the bee has laid up for its young. According to the same distinguished observer, the _Sapyga_ larva exhibits hypermetamorphosis (_i.e._ two consecutive forms), and in its young state destroys the egg of the bee; but his observations on this point are incomplete and need repetition. We have two species of _Sapyga_ in Britain; they differ in colour, and the sexes of _S. 5-punctata_ also differ in this respect; the abdomen, spotted with white in both sexes is in the female variegate with red. Smith found our British _Sapyga 5-punctata_ carrying caterpillars.

SUB-FAM. 5. RHOPALOSOMIDES.—_Antennae elongate, spinigerous; ocelli very
prominent; tarsi of peculiar structure, their claws bifid._

This sub-family has recently been proposed by Ashmead[47] for {101}an extremely rare American Insect that had previously been placed by Cresson among parasitic Hymenoptera. Westwood classed _Rhopalosoma_ among Diploptera, saying of it "animal quoad affinitates excrucians." We reproduce Westwood's figure, but not being acquainted with the Insect we can express no opinion as to whether it is allied to the Scoliidae or to the Sphegidae. The habits are, we believe, quite unknown.

FAM. 2. POMPILIDAE.

_Pronotum at the sides reaching the tegulae; hind body never definitely
pedicellate, though the first segment is sometimes elongate and conical;
hind legs long; eyes elliptic in form, not emarginate._

The Pompilidae are perhaps the most extensive and important of the groups of Fossores, and are distributed over all the lands of the globe, with the exception of some islands and of the inclement arctic regions. The sting of the Pompilidae, unlike that of most of the Fossores, inflicts a burning and painful wound; the creatures sometimes attain a length of two or three inches, and a sting from one of these giants may have serious results. Although there is considerable variety in the external form of the members of the group, the characters given above will enable a Pompilid to be recognised with approximate certainty. The elongation of the hind legs includes all the parts, so that while the femur extends nearly as far back as the extremity of the body—in dried examples at any rate—the tibiae and the long tarsi extend far beyond it; thus these Insects have great powers of running; they are indeed remarkable for extreme activity and vivacity. They may frequently be seen running rapidly on the surface of the ground, with quivering wings and vibrating antennae, and are probably then employed in the search for prey, or some other of the operations connected with providing a store of food for their young. Spiders appear to be their special, if not their only, prey. Several authors have recorded details as to the various ways in which the prey is attacked. Fabre has observed the habits of several species, and we select his account of the _modus operandi_ of species of the genera _Pompilus_ and _Calicurgus_, in their attacks on poisonous spiders that inhabit holes in the ground or in walls. The wasp goes to the mouth of the spider's burrow, and the latter then dashes to the entry, apparently enraged at the audacity of its persecutor.

{102}

The _Calicurgus_ will not actually enter a burrow when there is a spider in it, because if it did so the spider would speedily dispose of the aggressor by the aid of its poisonous fangs. The _Calicurgus_, therefore, has recourse to strategy with the object of getting the spider out of its nest; the wasp seizes its redoubtable foe by one foot and pulls; probably it fails to extract the spider, and in that case rapidly passes to another burrow to repeat its tactics; sooner or later a spider is in some moment of inattention or incapacity dragged from its stronghold, and, being then comparatively helpless, feels itself at a disadvantage and offers but a feeble resistance to the wasp, which now pounces on its body and immediately inflicts a sting between the fangs of the foe, and thus at once paralyses these dangerous weapons; thereafter it stings the body of the spider near to the junction of the abdomen and cephalothorax, and so produces complete inactivity. Having secured its prey, the wasp then seeks a suitable hole in which to deposit it; probably an empty burrow of a spider is selected for the purpose, and it may be at a height of several feet in a wall; the Hymenopteron, walking backwards, drags its heavy prey up the wall to bring it to the den. When this is accomplished an egg is deposited on the spider, and the wasp goes in search of a fragment or two of mortar, with which the mouth of the burrow is finally blocked. Fabre's accounts refer to the habits of several species, and give a good insight into some points of the instincts of both the spider and the wasp. It seems that a sense of superiority is produced in one or other of the foes, according as it feels itself in suitable conditions; so that though a spider out of its burrow and on the ground is speedily vanquished by the Pompilid, yet if the two be confined together in a vase, both are {103}shy and inclined to adopt defensive or even evasive tactics, the result probably being that the wasp will be killed by the spider during the night, that being the period in which the attacking powers of the spider are more usually brought into play.

It seems to be the habit of some _Pompilus_ to procure a victim before they have secured a place for its reception; and Fabre took advantage of this fact, and made very interesting observations on some points of the instinct of these wasps. Having found a _Pompilus_ that, after having caught a spider and paralysed it, was engaged in making a retreat for its reception, he abstracted the booty, which was deposited at the top of a small tuft of vegetation near to where the _Pompilus_ was at work. In this case the burrow in course of preparation was subterranean, and was formed by the _Pompilus_ itself, which therefore could not, while it was engaged underground, see what took place near it. It is the habit of the wasp to leave its work of excavation from time to time, and to visit the prey as if to assure itself of the safety of this object, and to enjoy the satisfaction of touching it with the mouth and palping it. Desirous of testing the wasp's memory of locality, Fabre took the opportunity, while the Insect was working at the formation of its burrow, of removing, as we have said, the booty from the place where it had been deposited, and putting it in another spot some half-yard off. In a short time the _Pompilus_ suspended work and went straight to the spot where it had deposited its property, and finding this absent, entered on a series of marches, counter-marches, and circles round the spot where it had left the prey, as if quite sure that this was really the place where the desired object ought to be. At last convinced that the paralysed prey was no longer where it had been placed, the _Pompilus_ made investigations at a greater distance and soon discovered the spider. Fabre recounts that its movements then appeared to indicate astonishment at the change of position that it thus ascertained to have occurred. The wasp, however, soon satisfied itself that this was really the very object it was seeking, and seizing the spider by the leg slightly altered its position by placing it on the summit of a small tuft of vegetation; this latter proceeding being apparently always carried out by this species of _Pompilus_. Then it returned to its excavation, and Fabre again removed the spider to a third spot; the wasp when it next rested from its work made its way {104}immediately to the second spot, where it had last left the spider, thus showing that it possessed an accurate memory for locality; the wasp was very much surprised at the absence of the valued prize and persisted in seeking it in the immediate vicinity without once returning to the place where it had been first located. Fabre repeated this manoeuvre five times, and the _Pompilus_ invariably returned at once to the spot where it had last left its prey. The acute memory for localities displayed by this Insect seems to be more or less general throughout the Aculeate Hymenoptera, and is of very great importance to them. The power of finding the object appears to depend on sight, for when Fabre, after removing the spider to a fresh spot, made a slight depression in the ground, placed the spider in it and covered it over with a leaf, the wasp did not find it. At the same time, the Insect's sight must be a very different sense from our own, for the wasp, when seeking its lost booty, frequently passed within a couple of inches of it without perceiving it, though it was not concealed.

Belt gives an example of the habits of the Mexican _Pompilus polistoides_. He noticed it, when hunting for spiders, make a dart at a web in the centre of which a spider was stationed; by this movement the creature was frightened and fell to the ground, where it was seized by the wasp and stung. The _Pompilus_ then dragged its prisoner up a tree and afterwards flew off with it, the burden being probably too heavy for conveyance to the nest without the vantage of an elevation to start from.

Several modifications adopted by Pompilidae in their mode of stinging their spider-victims have been recorded by Ferton; these we cannot allude to in detail, but will nevertheless mention that one species stings the body of its spider-prey at random, and that in other cases it would appear that the paralysis of the spider is evanescent. In short, there are various degrees of perfection in the details of the art of stinging.

The most remarkable of the forms of Pompilidae are the numerous species of _Pepsis_, a genus peculiar to America, whence upwards of 200 species are already known.[48] Some of them attain a length of two inches or more, and are able to conquer the largest spiders; even the formidable _Mygale avicularis_ succumbs to their agility and skill. Some of these _Pepsis_ have beautifully coloured wings; according to Cameron, this may be {105}due to scales. _P. formosus_, Say, is called in Texas the tarantula-killer; according to Buckley, its mode of attack on the huge spider is different from that made use of by its European ally. When it discovers a tarantula it flies "in circles in the air, around its victim. The spider, as if knowing its fate, stands up and makes a show of fighting, but the resistance is very feeble and of no avail. The spider's foe soon discovers a favourable moment and darts upon the tarantula, whom it wounds with its sting, and again commences flying in circles." The natural retreat of this huge spider, _Mygale hentzii_, is in holes in the ground, and this account does not inform us whether the spider allows itself to be overcome when in its nest, or is only attacked when out of its retreat.

The genus _Mygnimia_ includes a very large number of species, and has a wider geographical distribution than _Pepsis_, being found in the tropical regions of both the Old and New Worlds, some of them rivalling in size and ferocity the larger specimens of the genus _Pepsis_. In the Insects of this genus there is usually a more or less distinct small space of more pallid colour on the middle of each front wing. _Parapompilus_ is a curious genus consisting of Insects of a great variety of peculiar coloration, and having the wings short, so as to be of little use for flight. _P. gravesii_ is an inhabitant of Chili.

_Agenia carbonaria_ and _A. hyalipennis_ are small and feeble Insects inhabiting the south of Europe. _A. carbonaria_ extends to the south of England. They construct, as nests for their offspring, small earthenware vessels, differing in form according to the species, those of _A. hyalipennis_ being vase-like in shape, while those of _A. carbonaria_ are contracted near the mouth, something after the fashion of a wide-mouthed bottle. The Insect is able by some means—Fabre thinks by the use of saliva—to varnish the interior of the vessel so that it will not absorb water; the outside of the cells is, however, not so protected, and speedily crumbles away when exposed to the action of water; hence the vessel is placed in a protected situation, such as in a tree-stump, or a hole in a wall, or even in an empty snail-shell under a heap of stones. The cells are stored with spiders that have been paralysed by stinging and that serve as food for the larva of the _Agenia_. The larva of _A. carbonaria_ has been described, and some particulars as to its habits have been given by Verhoeff. {106}It has been stated that this wasp does not paralyse its prey by stinging, but substitutes a process of biting to prevent the spider from hurting the larva that is to feed on it; and Verhoeff's observations seem to show that the legs of the spider are broken by some proceeding of the kind. The _Agenia_ larva is of peculiar shape, the head not being inflexed, while the pleurae of each segment, from the second onwards, are prominent, so as to give the outline of the body a scalloped appearance. This larva is much infested by an Ichneumon that devours, it appears, not only the larva itself, but also the spider that was destined to be food for the larva. Verhoeff seems to have found some evidence that _Pompilus sericeus_ may also be a parasite on the _Agenia_.

The construction of earthenware cells, instead of the burrows usual in Pompilidae, by the species of this genus is one of the cases alluded to in our introductory remarks as to allied Fossores exhibiting different habits. Mr. Pride has recently sent us from Brazil similar earthen vessels constructed by some Pompilid.

The habits of Pompilids of the genus _Ceropales_ are analogous to those of the parasitic bees. Pérez has recently given us information as to a very curious form of parasitism in this genus; he says that when a _Pompilus_ has obtained a spider as provision for its young, it is pursued by a _Ceropales_, which lays an egg on the spider, thus as it were substituting in advance its own young for that of the _Pompilus_. Information as to the subsequent course of events in this case is not at present forthcoming. In another case a _Ceropales_ was observed to oviposit on the spider, not while this is being carried in, but subsequently by entering the nest for the purpose; a habit quite similar to that of some parasitic bees. Ferton has recently made the unexpected discovery that some _Pompilus_ act as robbers; one individual taking away by force the spider that another has captured and is carrying off.

Lichtenstein described a Pompilid larva, that he afterwards ascertained to be _Calicurgus hyalinatus_, as possessing the extraordinary habit of feeding as an external parasite fixed to the dorsal surface of a spider; thus repeating, it would appear, the habits of some of the Ichnemonidae, though the perfect Insect (Fig. 143) does not differ in structure from its congeners. Emery has given an account of some Pompilids that do not bury their prey, but after stinging it and depositing an egg, simply leave the spider on the spot.

{107}Buller has described the habits of a Pompilid in New Zealand; his account is interesting because it shows a remarkable similarity in the proceedings of this antipodean wasp to those of its congeners on our own side of the world. The species is not scientifically named, but it appears that it is known in New Zealand as "the Mason-bee." It forms a nest of yellow clay consisting apparently of about eight cells, each of which is filled with one or more spiders in a paralysed condition. The figure given of the larva of this Insect by Buller shows it to possess a peculiarly formed head.

It is pleasing to find that Pompilidae do not make use of cruel methods when others will serve their purpose. We are informed that a large Australian Pompilid—_Priocnemis bicolor_—may find a _Cicada_ sucking sap from a hole it has pierced in a tree. The _Priocnemis_ has not the art of making the puncture necessary to procure sap, so the wasp seizes the _Cicada_, and shakes it till it leaves its hold and flies away, when the _Priocnemis_ takes its place and sips the sap. It is added that the wasp never hurts the Cicada.

FAM. 3. SPHEGIDAE.

_Pronotum free from the tegulae; when the stigmatic lobes extend as far
back as the wing-insertion, they are placed below it and separated by a
space from it._

This large assemblage of Fossores is the one about which the greatest difference of opinion prevails. It is based entirely on the prothoracic characters mentioned above, and cannot be looked on as natural. We shall, however, follow Kohl[49] in treating for the present as only one family the divisions considered by many as distinct families. They are ten in number.

SUB-FAM. 1. SPHEGIDES.—_Hind body with a slender pedicel of variable
length; two spurs on the middle tibia. The propodeum usually horizontally
elongate_.[50]

This group includes a great number of species, about 200 of which are referred to the genus _Sphex_.

{108}The habits of one species of this genus have been fully described by Fabre; he assigns to the species the name of _S. flavipennis_, but Kohl considers that it is more probably _S. maxillosus_. This Insect forms its nests, in the South of France, in the ground, excavating a main shaft with which are connected cells intended for the reception of the provisions for the young. The entrance to the burrow is formed by piercing a hole in the side of a very slight elevation of the soil. Thus the entrance to the construction consists of a horizontal gallery, playing the part of a vestibule, and this is used by the _Sphex_ as a place of retreat and shelter for itself; at the end of the vestibule, which may be two or three inches long, the excavation takes an abrupt turn downwards, extending in this manner another two or three inches, and terminating in an oval cell the larger diameter of which is situate in a horizontal plane. When this first cell has been completed, stored with food, and an egg laid in it, the entrance to it is blocked up, and another similar cell is formed on one side; a third and sometimes a fourth are afterwards made and provisioned, then the Insect commences anew, and a fresh tunnel is formed; ten such constructions being the number usually prepared by each wasp. The Insect works with extreme energy, and as the period of its constructive activity endures only about a month, it can give but two or three days to the construction and provisioning of each of its ten subterranean works. The provisions, according to Fabre, consist of a large species of field-cricket, of which three or four individuals are placed in each cell. Kohl states, however, that in Eastern Europe an Insect that he considers to be the same species as Fabre's _Sphex_, makes use of locusts as provisions, and he thinks that the habit may vary according to the locality or to the species of Orthoptera that may be available in the neighbourhood. However that may be, it is clear from Fabre's account that this part of the _Sphex's_ duties do not give rise to much difficulty. The cricket, having been caught, is paralysed so that it may not by its movements destroy the young larva for whose benefit it is destined. The _Sphex_ then carries it to the burrow to store it in one of the cells; before entering the cell the Insect is in the habit of depositing its prey on the ground, then of turning round, entering the burrow backwards, seizing as it does so the cricket by the antennae, and so dragging it into the cell, itself going {109}backwards. The habit of depositing its prey on the ground enabled Fabre to observe the process of stinging; this he did by himself capturing a cricket, and when the wasp had momentarily quitted its prey, substituting the sound cricket for the paralysed one. The _Sphex_, on finding this new and lively victim, proceeds at once to sting it, and pounces on the cricket, which, after a brief struggle, is overcome by the wasp; this holds it supine, and then administers three stings, one in the neck, one in the joint between the pro- and meso-thorax, and a third at the base of the abdomen, these three spots corresponding with the situation of the three chief nervous centres governing the movements of the body. The cricket is thus completely paralysed, without, however, being killed. Fabre proved that an Insect so treated would survive for several weeks, though deprived of all power of movement. Three or four crickets are placed by the wasp in each cell, 100 individuals or upwards being thus destroyed by a single wasp. Although the sting has such an immediate and powerful effect on the cricket, it occasions but a slight and evanescent pain to a human being; the sting is not barbed, as it is in many bees and true wasps, and appears to be rarely used by the Insect for any other purpose than that of paralysing its victims. The egg is laid by the _Sphex_ on the ventral surface of the victim between the second and third pairs of legs. In three or four days the young larva makes its appearance in the form of a feeble little worm, as transparent as crystal; this larva does not change its place, but there, where it was hatched, pierces the skin of the cricket with its tiny head, and thus begins the process of feeding; it does not leave the spot where it first commenced to feed, but gradually enters by the orifice it has made, into the interior of the cricket. This is completely emptied in the course of six or seven days, nothing but its integument remaining; the wasp-larva has by this time attained a length of about 12 millimetres, and makes its exit through the orifice it entered by, changing its skin as it does so. Another cricket is then attacked and rapidly consumed, the whole stock being devoured in ten or twelve days from the commencement of the feeding operations; the consumption of the later-eaten crickets is not performed in so delicate a manner as is the eating of the first victim. When full-grown, the process of forming a cocoon commences: this is a very elaborate operation, for the encasement consists of three layers, in {110}addition to the rough silk that serves as a sort of scaffolding on the exterior: the internal coat is polished and is of a dark colour, owing to its being coloured with a matter from the alimentary canal: the other layers of the cocoon are white or pale yellow. Fabre considers that the outer layers of the cocoon are formed by matter from the silk-glands, while the interior dark coat is furnished by the alimentary canal and applied by the mouth of the larva: the object of this varnish is believed to be the exclusion of moisture from the interior of the cocoon, the subterranean tunnels being insufficient for keeping their contents dry throughout the long months of winter. During the whole of the process of devouring the four crickets, nothing is ejected from the alimentary canal of the larva, but after the cocoon is formed the larva ejects in it, once for all, the surplus contents of the intestine. Nine months are passed by the Insect in the cocoon, the pupal state being assumed only towards the close of this period. The pupa is at first quite colourless, but gradually assumes the black and red colour characteristic of the perfect wasp. Fabre exposed some specimens of the pupa to the light in glass tubes, and found that they went through the pupal metamorphosis in just the same manner as the pupae that remained in the darkness natural to them during this stage of their existence.

_Sphex coeruleus_ is frequently stated to have the habit of provisioning its nests with both Orthoptera and Spiders; but Kohl considers with reason that this record is, as regards spiders, a mistake, arising probably from a confusion with some other Insect of similar appearance, such as _Pelopaeus_ (_Sceliphron_) _coeruleus_. _S. coeruleus_ is no doubt the same as _S._ (_Chlorion_) _lobatus_, which Rothney observed in East India, provisioning its nests with Orthoptera. He discovered a nest in process of construction, and during the absence of the mother-wasp abstracted from the burrow a large field-cricket that she had placed in it; he then deposited the Orthopteron near the cell; the parent _Sphex_ on returning to work entered the tunnel and found the provision placed therein had disappeared; she came out in a state of excitement, looked for the missing cricket, soon discovered it, submitted it to the process of malaxation or kneading, and again placed it in the nest, after having cleared it from some ants that had commenced to infest it. She then disappeared, and Rothney repeated the experiment; in due course the same series {111}of operations was performed, and were repeated many times, the _Sphex_ evidently acting in each case as if either the cricket had disappeared owing to its being incompletely stunned, or to its having been stolen by ants. Finally, the observer placed the cricket at a greater distance from the nest, when it recovered from the ill-treatment it had received sufficiently to make its escape. The points of interest in this account are the fact that the cricket was only temporarily paralysed, and that the wasp was quite able to cope with the two special difficulties that must frequently occur to the species in its usual round of occupations.

The genus _Ammophila_ is of wide distribution, and its species make vertical tunnels in the ground. The habits of some of the species found in France have been described by Fabre. The Insect does not inhabit the burrow while it is in process of formation, but quits it; and some of the species temporarily close the entry to the incomplete nest with a stone. The tunnel is a simple shaft with a single cell at its termination; this is stored with caterpillars, the different species of _Ammophila_ selecting different grubs for the purpose. _A. hirsuta_ hibernates in the perfect state, and carries on its work in the spring; it chooses a single larva of considerable size belonging to one of the nocturnal Lepidoptera, and this it paralyses by a series of about nine stings, of which one is implanted in each segment from the first thoracic ring backwards; it forms the burrow only after the food to be placed therein has been obtained. The caterpillar used is subterranean in habit, and the _Ammophila_ detects the larva by some sense, the nature of which appears at present quite uncertain. _A. holosericea_ chooses smaller larvae of the family Geometridae, and uses only one or two stingings to paralyse each larva; several caterpillars are used to provision a single cell, and they are often selected of different colours.

Marchal has also published an important account of the proceedings of _A. affinis_; he confirms Fabre's observations, and even adds to their interest by suggesting that the _Ammophila_ administers special stings for the purpose of paralysing the mandibles of the caterpillar and depriving it of any power of afterwards injuring the larva that will feed on it. He thinks the mother-_Ammophila_ herself profits by appropriating an exudation from the victim.

Some species of Sphegides have the curious habit of choosing {112}the interiors of human habitations as the spots most suitable for the formation of their own domestic establishments. Fabre has given a charming account of the habits of _Pelopaeus_ (_Sceliphron_) _spirifex_, a species that inhabits the South of Europe, and that forms its nests in the cottages of the peasants. The spot usually selected is a nook in the broad, open fireplace, out of reach of the flames, though not of the smoke; here the _Pelopaeus_ forms a nest of earth, consisting of ten to fifty cells, the material being mud or clay brought in little balls by the aid of the Insect's mandibles; about twenty visits are required in order to complete one cell, so that for the construction of a large nest of fifty cells, about one thousand visits must be made by the Insect. It flies in and out of the house apparently not at all incommoded by the human habitants, or by the fact that the peasant's potage may be simmering on the fire quite close to where the fearless little creature is carrying on its architectural operations. The cells are stored with spiders, of which the wasp has to bring a plentiful supply, so that its operations extend over a considerable period. The prey is captured by the _Pelopaeus_ whilst on the wing, and carried off at once, being probably stung by the wasp during the process of transit; apparently it is killed by the operation, not merely paralysed. Only small spiders are taken by this species, and the larva of the _Pelopaeus_ consumes them in a short time, one by one, before the process of decomposition sets in; the egg, too, is laid on the first spider introduced, and this is of course at the bottom of the cell, so that the spiders are eaten by the wasp's larva in the order in which they were brought to the cell. The cell is sealed up when full, the number of spiders placed in it being on the average about eight. The larva completes its task of consuming the store in about ten days, and then forms a cocoon for its metamorphosis. Two or three generations are produced in a single year, the autumnal one passing eight or nine months in the clay cells, which are lodged in a nook of the peasant's hearth, and exposed to the smoke of his fire during all the months of winter. _Pelopaeus_ (_Sceliphron_) is a genus including many species;[51] several of them are known {113}to be specially attached to the habitations of human beings. Roth has given an account of the habits of _P._ (_Sceliphron_) _laetus_ in Australia; he says that in some parts it is very difficult to keep these wasps out of the houses; the nest is formed of mud, and constructed on the furniture or in any part of a room that suits the fancy of the Insect. This it must be admitted is, according to human ideas, liable to the charge of being very capricious. Roth timed a wasp building its nest, and found that it brought a fresh load of mud every two or three minutes. If the wasp be allowed to complete the nest undisturbed, she does so by adding to the exterior diagonal streaks of mud, so giving to the nest the look of a small piece of the bark of a common acacia. The construction consists of from ten to twenty cells, and when completed is provisioned with spiders for the use of the young. This wasp is much pestered by parasites, some of which prevent the development of the larvae by consuming the spiders intended by the mother-wasp for its young. A fly, of the Order Diptera, is said to follow the wasp when carrying a spider, and to deposit also an egg on the food; as the Dipterous larvae have more rapid powers of assimilation, the _Pelopaeus_ larvae are starved to death; and their mildewed remains may be found in the cell, after their enemies have become fully developed and have flown away. Another parasite is said to eat the wasp-larva, and attains this end by introducing an egg through the mud wall and the cocoon of the wasp—a habit that seems to indicate a _Leucospid_ parasite. _Tachytes australis_, a wasp of the sub-family Larrides also dispossesses this _Pelopaeus_ in a manner we shall subsequently describe. This fragment of natural history from Australia has a special interest, for we find repeated there similar complex biological relations to those existing in the case of the European congeners.

_P._ (_Sceliphron_) _madraspatanus_ is common in the north-west provinces of Hindostan, and is called the "mud-dauber" by the European residents. According to Horne it constructs its cells in the oddest places, but chiefly about the inhabited apartments in houses. It is perfectly fearless when engaged in building: the cells are four to six in number, and are usually provisioned with spiders to the number of about twenty. On one occasion it was observed that green caterpillars were stored instead of {114}spiders. The species is said to be protected by a peculiar odour as well as by its sting; it is also stated that it disguises its edifice when completed by making it look like a dab of mud, and on one occasion "rays of mud were observed round the nest, even more exactly imitating a lump of mud thrown with some force." _P._ (_Sceliphron_) _bilineatus_, formerly thought to be a variety of _P. madraspatanus_, builds its nests in hedges and trees.

SUB-FAM. 2. AMPULICIDES.—_Prothorax long and narrow, forming a neck in
front; clypeus beak-like; four submarginal cells, the outer one being
complete; metathorax elongate, the posterior part of the metasternum
deeply divided to allow a perfect inflection of the abdomen._

This is one of the smallest of the divisions of the Sphegidae, but has a very wide distribution, being represented in both the Eastern and Western Hemispheres. It is allied to the Sphegides, but differs by the prolongation of the neck and of the head, and by the articulation between the petiole and thorax being placed on the under surface of the body; the wing-nervures are said to be of inferior importance owing to their frequently differing in individuals of the same species. These Insects appear to be rare in individuals, as well as few in species, and but little has been recorded as to their habits; but it is known that they live on cockroaches. Perkins has given a brief sketch of the habits of _Ampulex sibirica_ that is of great interest, but requires confirmation. He says that this Insect, in West Africa, enters apartments where cockroaches abound, and attacking one, that may probably be four times its own size, succeeds, after a struggle, in stinging it; the cockroach instantly becomes quiet and submissive, and suffers itself to be led away and placed in confinement in some {115}spot such as a keyhole, and in one case was apparently prevented from afterwards escaping, by the wasp carrying some heavy nails into the keyhole. The larva of the _Ampulex_ may be presumed to live on the Blattid, as it is added that dead bodies of the cockroaches are frequently found with the empty cocoon protruding from them. This account, if correct, points to some features in the habits of this Insect that are unique. A remark made by Rothney in reference to the habits of _A._ (_Rhinopsis_) _ruficornis_ seems to indicate some similar instinct on the part of that species; he says, "I also saw two or three of these wasps collar a peculiar cockroach by the antennae and lead it off into a crack in the bark, but as the cockroach reappeared smiling each time, I don't know what was up." The same observer records that this species associates with _Sima rufonigra_, an ant it greatly resembles in appearance, as well as with a spider that is also of similar appearance (Fig. 72). Schurr has given a brief account of the proceedings of _Ampulex compressa_, and his statements also tend to confirm the correctness of Perkins' report. The habits of a species of _Ampulex_ were partially known to Réaumur, who described them on the authority of M. Cossigni. The species is believed to be _A. compressa_, which occurs not only in East India, but also in the island of Bourbon, the locality where M. Cossigni made his observation: his account is, like the others, a mere sketch of certain points observed, the most important of which is that when _Ampulex_ cannot introduce the cockroach into a hole that it has selected as suitable, it bites off some portions of the body in order to reduce the poor Insect to the necessary extent.

From these fragmentary observations it would appear that the sting of the _Ampulex_ has not so powerful a paralysing effect as that of most other Fossores; and that the _Ampulex_ does not form any nest, but takes advantage of suitable holes and crevices to store the victim in; also that it displays considerable ingenuity in the selection of materials with which to block up the cavity in which it has placed the partially incapacitated creature.

The genus _Dolichurus_ is by some entomologists considered the type of a sub-family allied to the Ampulicides; it long consisted of a small and rare European Insect, but some exotic species have recently been added to it. It will probably prove not {116}sufficiently distinct from Ampulicides, although the pronotum is much shorter, but Handlirsch has recently observed that the European species attacks Blattidae as do the normal Ampulicides; and Ferton has recorded that _D. haemorrhous_ lives at the expense of _Loboptera decipiens_, the wasp depositing its egg on the left intermediate femur of the prey. This is placed in a solitary cell, and is entirely consumed by the larva, life being preserved till within a few hours of the end of the repast, which occupies altogether eight days.

SUB-FAM. 3. LARRIDES.—_Hind body not pedicellate, or with only a short
pedicel; one spur on the middle tibia; labrum inconspicuous. Marginal
cell of the front wings appendiculate,[52] or mandibles excised
externally, or both._

This group is by some writers called Tachytides instead of Larrides, as owing to a change of nomenclature _Tachytes_ may now be considered its principal genus. It is in connection with this and the neighbouring sub-families of Sphegidae that some of the greatest taxonomical difficulties exist. We include in Larrides the "_Miscophus_ group" of Kohl.

The species of the genus _Tachytes_ seem to have habits very similar to those of the genus _Sphex_; they form shafts in the earth and provision them with Orthoptera; like the _Sphex_ and other Fossores, they have the habit, when they fly to their tunnel with a victim, of depositing it for a short time on the ground close to the mouth of the burrow while they turn round and enter backwards; and, after doing this they again seize their prey and drag it into the burrow. Fabre availed himself of an opportunity to remove the prey while the Hymenopteron was entering the hole alone; as a result it had to come out again to seek the object; this it soon found, and carried to the hole, relinquishing it again as usual while it turned round; Fabre repeated the operation several times, and always with the same result; the wasp, though it might have kept hold of the victim while it turned, and thus have saved itself from losing the precious object, never did so.

{117}One species of _Tachytes_ in the south of France selects as its prey Orthoptera of the family Mantidae, Insects of a highly ferocious disposition, and provided with most powerful front legs, capable of cutting in two by a single act the body of an aggressor like the _Tachytes_; the latter is, however, by no means dismayed by the arms of its future victim, but hovering above the latter for some time, as if to confuse it, and causing it repeatedly to turn its very mobile head, the _Tachytes_ at last pounces down and instantaneously stings the _Mantis_ in the nerve centre between the formidable arms, which at once are reduced to incapacity; subsequently the _Tachytes_ paralyses each of the other pairs of legs, and then carries off its victim.

_Larra anathema_ chooses mole-crickets as the viand for its young, and _Tachysphex panzeri_ selects grasshoppers of the family Acridiidae. _Larra pompiliformis_ (= _Tachytes niger_, Fabre) sometimes associates itself with _Sphex flavipennis_ (_? S. maxillosus_, according to Kohl), forming its burrow amidst the works of a colony of that species, and making use, like the _Sphex_, of crickets for provender. This led Fabre to believe that the _Larra_ stole its prey from the _Sphex_, but he has since withdrawn this indictment, and declares that the _Larra_ obtains its crickets by the more honourable, if not more humane, process of catching and stinging them itself. Smith has informed us, on the faith of his own observation, that _L. pompiliformis_ uses both Lepidopterous larvae and grasshoppers for its stores.