Chapter II: Arthropods Which Are Directly Poisonous (2)

It is well known that mosquitoes, when they bite, inject into the wound a minute quantity of poison. The effect of this varies according to the species of mosquito and also depends very much on the susceptibility of the individual. Soon after the bite a sensation of itching is noticed and often a wheal, or eminence, is produced on the skin, which may increase to a considerable swelling. The scratching which is induced may cause a secondary infection and thus lead to serious results. Some people seem to acquire an immunity against the poison.

The purpose of this irritating fluid may be, as Reaumur suggested, to prevent the coagulation of the blood and thus not only to cause it to flow freely when the insect bites but to prevent its rapid coagulation in the stomach. Obviously, it is not developed as a protective fluid, and its presence subjects the group to the additional handicap of the vengeance of man.

As to the origin of the poison, there has been little question, until recent years, that it was a secretion from the salivary glands. Macloskie (1888) showed that each gland is subdivided into three lobes, the middle of which differs from the others in having evenly granulated contents and staining more deeply than the others (fig. 24). This middle lobe he regarded as the source of the poison. Bruck, (1911), by the use of water, glycerine, chloroform, and other fluids, extracted from the bodies of a large number of mosquitoes a toxine which he calls _culicin_. This he assumes comes from the salivary glands. Animal experimentation showed that this extract possessed hemolytic powers. Inoculated into the experimenter's own skin it produced lesions which behaved exactly as do those of mosquito bites.

Similarly, most writers on the subject have concurred with the view that the salivary glands are the source of the poison. However, recent work, especially that of Nuttall and Shipley (1903), and Schaudinn (1904), has shown that the evidence is by no means conclusive. Nuttall dissected out six sets (thirty-six acini) of glands from freshly killed _Culex pipiens_ and placed them in a drop of salt solution. The drop was allowed to dry, it being thought that the salt crystals would facilitate the grinding up of the glands with the end of a small glass rod, this being done under microscopic control. After grinding up, a small drop of water was added of the size of the original drop of saline, and an equal volume of human blood taken from the clean finger-tip was quickly mixed therewith, and the whole drawn up into a capillary tube. Clotting was not prevented and no hemolysis occurred. Salivary gland emulsion added to a dilute suspension of corpuscles did not lead to hemolysis. This experiment was repeated a number of times, with slight modification, but with similar results. The data obtained from the series "do not support the hypothesis that the salivary glands, at any rate in _Culex pipiens_, contain a substance which prevents coagulation."

Much more detailed, and the more important experiments made along this line, are those of Schaudinn (1904). The results of these experiments were published in connection with a technical paper on the alternation of generations and of hosts in _Trypanosoma_ and _Spirochaeta_, and for this reason seem to have largely escaped the notice of entomologists. They are so suggestive that we shall refer to them in some detail.

Schaudinn observed that the three oesophageal diverticula (commonly, but incorrectly, known as the "sucking stomach") (fig. 24) usually contain large bubbles of gas and in addition, he always found yeast cells. On the ground of numerous observations, Schaudinn was convinced that these yeast plants are normal and constant commensals of the insect. He regarded them as the cause of the gas bubbles to be found in diverticula. It was found that as the insect fed, from time to time the abdomen underwent convulsive contractions which resulted in the emptying of the oesophageal diverticula and the salivary glands through blood pressure.

In order to test the supposed toxic action of the salivary glands, Schaudinn repeatedly introduced them under his skin and that of his assistant, in a drop of salt solution, and never obtained a suggestion of the irritation following a bite of the insect, even though the glands were carefully rubbed to fragments after their implantation. Like Nuttall, he failed to get satisfactory evidence that the secretion of the salivary glands retarded coagulation of the blood.

He then carefully removed the oesophageal diverticula with their content of yeast and introduced them into an opening in the skin of the hand. Within a few seconds there was noticeable the characteristic itching irritation of the mosquito bite; and in a short time there appeared reddening and typical swelling. This was usually much more severe than after the usual mosquito bite, and the swelling persisted and itched longer. This was because by the ordinary bite of the mosquito most of the yeast cells are again sucked up, while in these experiments they remained in the wound. These experiments were repeated a number of times on himself, his assistant and others, and always with the same result. From them Schaudinn decided that the poisonous action of the mosquito bite is caused by an enzyme from a commensal fungus. These conclusions have not, as yet, been satisfactorily tested.

Relief from the effect of the mosquito bite may be obtained by bathing the swellings with weak ammonia or, according to Howard, by using moist soap. The latter is to be rubbed gently on the puncture and is said to speedily allay the irritation. Howard also quotes from the _Journal of Tropical Medicine and Hygiene_ to the effect that a few drops of a solution of thirty to forty grains of iodine to an ounce of saponated petroleum rubbed into the mosquito bite, or wasp sting, allay the pain instantaneously.

Methods of mosquito control will be discussed later, in considering these insects as parasites and as carriers of disease.

STINGING INSECTS

The stinging insects all belong to the order HYMENOPTERA. In a number of families of this group the ovipositor is modified to form a sting and is connected with poison-secreting glands. We shall consider the apparatus of the honey-bee and then make briefer reference to that of other forms.

APIS MELLIFICA, THE HONEY BEE--The sting of the worker honey-bee is situated within a so-called sting chamber at the end of the abdomen. This chamber is produced by the infolding of the greatly reduced and modified eighth, ninth and tenth abdominal segments into the seventh.[D] From it the dart-like sting can be quickly exserted.

The sting (fig. 25) is made up of a central shaft, ventro-laterad of which are the paired _lancets_, or darts, which are provided with sharp, recurved teeth. Still further laterad lie the paired whitish, finger-like _sting palpi_. Comparative morphological as well as embryological studies have clearly established that these three parts correspond to the three pairs of gonopophyses of the ovipositor of more generalized insects.

An examination of the internal structures (fig. 26) reveals two distinct types of poison glands, the acid-secreting and the alkaline-secreting glands, and a prominent poison reservoir. In addition, there is a small pair of accessory structures which have been called lubricating glands, on account of the supposed function of their product. The acid-secreting gland empties into the distal end of the poison reservoir which in turn pours the secretion into the muscular bulb-like enlargement at the base of the shaft. The alkaline secreting gland empties into the bulb ventrad of the narrow neck of the reservoir.

The poison is usually referred to as formic acid. That it is not so easily explained has been repeatedly shown and is evidenced by the presence of the two types of glands. Carlet maintains that the product of either gland is in itself innocent,--it is only when they are combined that the toxic properties appear.

The most detailed study of the poison of the honey-bee is that of Josef Langer (1897), who in the course of his work used some 25,000 bees. Various methods of obtaining the active poison for experimental purposes were used. For obtaining the pure secretion, bees were held in the fingers and compressed until the sting was exserted, when a clear drop of the poison was visible at its tip. This was then taken up in a capillary tube or dilute solutions obtained by dipping the tip of the sting into a definite amount of distilled water.

An aqueous solution of the poison was more readily obtained by pulling out the sting and poison sacs by means of forceps, and grinding them up in water. The somewhat clouded fluid was then filtered one or more times. For obtaining still greater quantities, advantage was taken of the fact that while alcohol coagulates the poison, the active principle remains soluble in water. Hence the stings with the annexed glands where collected in 96 per cent alcohol, after filtering off of the alcohol were dried at 40^o C., then rubbed to a fine powder and this was repeatedly extracted with water. Through filtering of this aqueous extract there was obtained a yellowish-brown fluid which produced the typical reactions, according to concentration of the poison.

The freshly expelled drop of poison is limpid, of distinct acid reaction, tastes bitter and has a delicate aromatic odor. On evaporation, it leaves a sticky residue, which at 100 degrees becomes fissured, and suggests dried gum arabic. The poison is readily soluble in water and possesses a specific gravity of 1.1313. On drying at room temperature, it leaves a residue of 30 per cent, which has not lost in poisonous action or in solubility. In spite of extended experiments, Langer was unable to determine the nature of the active principle. He showed that it was not, as had been supposed, an albuminous body, but rather an organic base.

The pure poison, or the two per cent aqueous solution, placed on the uninjured skin showed absolutely no irritating effect, though it produced a marked reaction on the mucus membrane of the nose or eye. A single drop of one-tenth per cent aqueous solution of the poison brought about a typical irritation in the conjunctiva of the rabbit's eye. On the other hand, the application of a drop of the poison, or its solution, to the slightest break in the skin, or by means of a needle piercing the skin, produced typical effects. There is produced a local necrosis, in the neighborhood of which there is infiltration of lymphocytes, oedema, and hyperaemia.

The effect of the sting on man (fig. 27) is usually transitory but there are some individuals who are made sick for hours, by a single sting. Much depends, too, on the place struck. It is a common experience that an angry bee will attempt to reach the eye of its victim and a sting on the lid may result in severe and prolonged swelling. In the case of a man stung on the cheek, Legiehn observed complete aphonia and a breaking out of red blotches all over the body. A sting on the tongue has been known to cause such collateral oedema as to endanger life through suffocation. Cases of death of man from the attacks of bees are rare but are not unknown. Such results are usually from a number of stings but, rarely, death has been known to follow a single sting, entering a blood vessel of a particularly susceptible individual.

It is clearly established that partial immunity from the effects of the poison may be acquired. By repeated injections of the venom, mice have been rendered capable of bearing doses that certainly would have killed them at first. It is a well-known fact that most bee-keepers become gradually hardened to the stings, so that the irritation and the swelling become less and less. Some individuals have found this immunity a temporary one, to be reacquired each season. A striking case of acquired immunity is related by the Roots in their "A B C and X Y Z of Bee Culture." The evidence in the case is so clear that it should be made more widely available and hence we quote it here.

A young man who was determined to become a bee-keeper, was so susceptible to the poison that he was most seriously affected by a single sting, his body breaking out with red blotches, breathing growing difficult, and his heart action being painfully accelerated. "We finally suggested taking a live bee and pressing it on the back of his hand until it merely pierced his skin with the sting, then immediately brushing off both bee and sting. This was done and since no serious effect followed, it was repeated inside of four or five days. This was continued for some three or four weeks, when the patient began to have a sort of itching sensation all over his body. The hypodermic injections of bee-sting poison were then discontinued. At the end of a month they were repeated at intervals of four or five days. Again, after two or three weeks the itching sensation came on, but it was less pronounced. The patient was given a rest of about a month, when the doses were repeated as before." By this course of treatment the young man became so thoroughly immunized that neither unpleasant results nor swelling followed the attacks of the insects and he is able to handle bees with the same freedom that any experienced bee-keeper does.

In an interesting article in the _Entomological News_ for November, 1914, J. H. Lovell calls attention to the fact that "There has been a widespread belief among apiarists that a beekeeper will receive more stings when dressed in black than when wearing white clothing. A large amount of evidence has been published in the various bee journals showing beyond question that honey-bees under certain conditions discriminate against black. A few instances may be cited in illustration. Of a flock of twelve chickens running in a bee-yard seven black ones were stung to death, while five light colored ones escaped uninjured. A white dog ran among the bee-hives without attracting much attention, while at the same time a black dog was furiously assailed by the bees. Mr. J. D. Byer, a prominent Canadian beekeeper, relates that a black and white cow, tethered about forty feet from an apiary, was one afternoon attacked and badly stung by bees. On examination it was found that the black spots had five or six stings to one on the white. All noticed this fact, although no one was able to offer any explanation. A white horse is in much less danger of being stung, when driven near an apiary, than a black one. It has, indeed, been observed repeatedly that domestic animals of all kinds, if wholly or partially black, are much more liable to be attacked by bees, if they wander among the hives, than those which are entirely white."

In order to test the matter experimentally, the following series of experiments was performed. In the language of the investigator:

"On a clear, warm day in August I dressed wholly in white with the exception of a black veil. Midway on the sleeve of my right arm there was sewed a band of black cloth ten inches wide. I then entered the bee-yard and, removing the cover from one of the hives, lifted a piece of comb with both hands and gently shook it. Instantly many of the bees flew to the black band, which they continued to attack as long as they were disturbed. Not a single bee attempted to sting the left sleeve, which was of course entirely white, and very few even alighted upon it."

"This experiment was repeated a second, third and fourth time; in each instance with similar results. I estimated the number of bees on the band of black cloth at various moments was from thirty to forty; it was evident from their behavior that they were extremely irritable. To the left white sleeve and other portions of my clothing they paid very little attention; but the black veil was very frequently attacked."

"A few days later the experiments were repeated, but the band of black cloth, ten inches wide, was sewed around my left arm instead of around the right arm as before. When the bees were disturbed, after the hive cover had been removed, they fiercely attacked the band of black cloth as in the previous experiences; but the right white sleeve and the white suit were scarcely noticed. At one time a part of the black cloth was almost literally covered with furiously stinging bees, and the black veil was assailed by hundreds. The bees behaved in a similar manner when a second hive on the opposite side of the apiary was opened."

"A white veil which had been procured for this purpose, was next substituted for the black veil. The result was most surprising, for, whereas in the previous experiments hundreds of bees had attacked the black veil, so few flew against the white veil as to cause me no inconvenience. Undoubtedly beekeepers will find it greatly to their advantage to wear white clothing when working among their colonies of bees and manipulating the frames of the hives."

When a honey-bee stings, the tip of the abdomen, with the entire sting apparatus, is torn off and remains in the wound. Here the muscles continue to contract, for some minutes, forcing the barbs deeper and deeper into the skin, and forcing out additional poison from the reservoir.

Treatment, therefore, first consists in removing the sting without squeezing out additional poison. This is accomplished by lifting and scraping it out with a knife-blade or the fingernail instead of grasping and pulling it out. Local application of alkalines, such as weak ammonia, are often recommended on the assumption that the poison is an acid to be neutralized on this manner, but these are of little or no avail. They should certainly not be rubbed in, as that would only accelerate the absorption of the poison. The use of cloths wrung out in hot water and applied as hot as can be borne, affords much relief in the case of severe stings. The application of wet clay, or of the end of a freshly cut potato is sometimes helpful.

In extreme cases, where there is great susceptibility, or where there may have been many stings, a physician should be called. He may find strychnine injections or other treatment necessary, if general symptoms develop.

OTHER STINGING FORMS--Of the five thousand, or more, species of bees, most possess a sting and poison apparatus and some of the larger forms are capable of inflicting a much more painful sting than that of the common honey-bee. In fact, some, like the bumble bees, possess the advantage that they do not lose the sting from once using it, but are capable of driving it in repeatedly. In the tropics there are found many species of stingless bees but these are noted for their united efforts to drive away intruders by biting. Certain species possess a very irritating saliva which they inject into the wounds.

The ants are not ordinarily regarded as worthy of consideration under the heading of "stinging insects" but as a matter of fact, most of them possess well developed stings and some of them, especially in the tropics, are very justly feared. Even those which lack the sting possess well-developed poison glands and the parts of the entire stinging apparatus, in so far as it is developed in the various species, may readily be homologized with those of the honey-bee.

The ants lacking a sting are those of the subfamily CAMPONOTINAE, which includes the largest of our local species. It is an interesting fact that some of these species possess the largest poison glands and reservoir (fig. 28) and it is found that when they attack an enemy they bring the tip of the abdomen forward and spray the poison in such a way that it is introduced into the wound made by the powerful mandibles.

More feared than any of the other Hymenoptera are the hornets and wasps. Of these there are many species, some of which attain a large size and are truly formidable. Phisalix (1897), has made a study of the venom of the common hornet and finds that, like the poison of the honey-bee, it is neither an albuminoid nor an alkaloid. Its toxic properties are destroyed at 120^o C. Phisalix also says that the venom is soluble in alcohol. If this be true, it differs in this respect from that of the bee. An interesting phase of the work of Phisalix is that several of her experiments go to show that the venom of hornets acts as a vaccine against that of vipers.

NETTLING INSECTS

So far, we have considered insects which possess poison glands connected with the mouth-parts or a special sting and which actively inject their poison into man. There remain to be considered those insects which possess poisonous hairs or body fluids which, under favorable circumstances, may act as poisons. To the first of these belong primarily the larvae of certain Lepidoptera.

LEPIDOPTERA

When we consider the reputedly poisonous larvae of moths and butterflies, one of the first things to impress us is that we cannot judge by mere appearance. Various species of Sphingid, or hawk-moth larvae, bear at the end of the body a chitinous horn, which is often referred to as a "sting" and regarded as capable of inflicting dangerous wounds. It would seem unnecessary to refer to this absurd belief if it were not that each summer the newspapers contain supposed accounts of injury from the "tomato worm" (fig. 29) and others of this group. The grotesque, spiny larva (fig. 30) of one of our largest moths, _Citheronia regalis_ is much feared though perfectly harmless, and similar instances could be multiplied.

But if the larvae are often misjudged on account of their ferocious appearance, the reverse may be true. A group of most innocent looking and attractive caterpillars is that of the flannel-moth larvae, of which _Lagoa crispata_ may be taken as an example. Its larva (fig. 31) has a very short and thick body, which is fleshy and completely covered and hidden by long silken hairs of a tawny or brown color, giving a convex form to the upper side. Interspersed among these long hairs are numerous short spines connected with underlying hypodermal poison glands. These hairs are capable of producing a marked nettling effect when they come in contact with the skin. This species is found in our Atlantic and Southern States. Satisfactory studies of its poisonous hairs and their glands have not yet been made.

_Sibine stimulea (Empretia stimulea)_, or the saddle-back caterpillar (fig. 32), is another which possesses nettling hairs. This species belongs to the group of Eucleidae, or slug caterpillars. It can be readily recognized by its flattened form, lateral, bristling spines and by the large green patch on the back resembling a saddle-cloth, while the saddle is represented by an oval, purplish-brown spot. The small spines are venomous and affect some persons very painfully. The larva feeds on the leaves of a large variety of forest trees and also on cherry, plum, and even corn leaves. It is to be found throughout the Eastern and Southern United States.

_Automeris io_ is the best known of the nettling caterpillars. It is the larva of the Io moth, one of the Saturniidae. The mature caterpillar, (fig. 33), which reaches a length of two and one-half inches, is of a beautiful pale green with sublateral stripes of cream and red color and a few black spines among the green ones. The green radiating spines give the body a mossy appearance. They are tipped with a slender chitinous hair whose tip is readily broken off in the skin and whose poisonous content causes great irritation. Some individuals are very susceptible to the poison, while others are able to handle the larvae freely without any discomfort. The larvae feed on a wide range of food plants. They are most commonly encountered on corn and on willow, because of the opportunities for coming in contact with them.

The larvae of the brown-tail moth (_Euproctis chrysorrhoea_) (fig. 35 and 36), where they occur in this country, are, on account of their great numbers, the most serious of all poisonous caterpillars. It is not necessary here, to go into details regarding the introduction of this species from Europe into the New England States. This is all available in the literature from the United States Bureau of Entomology and from that of the various states which are fighting the species. Suffice to say, there is every prospect that the pest will continue to spread throughout the Eastern United States and Canada and that wherever it goes it will prove a direct pest to man as well as to his plants.

Very soon after the introduction of the species there occurred in the region where it had gained a foothold, a mysterious dermatitis of man. The breaking out which usually occurred on the neck or other exposed part of the body was always accompanied by an intense itching. It was soon found that this dermatitis was caused by certain short, barbed hairs of the brown-tail caterpillars and that not only the caterpillars but their cocoons and even the adult female moths might harbor these nettling hairs and thus give rise to the irritation. In many cases the hairs were wafted to clothing on the line and when this was worn it might cause the same trouble. Still worse, it was found that very serious internal injury was often caused by breathing or swallowing the poisonous hairs.

The earlier studies seemed to indicate that the irritation was purely mechanical in origin, the result of the minute barbed hairs working into the skin in large numbers. Subsequently, however, Dr. Tyzzer (1907) demonstrated beyond question that the trouble was due to a poison contained in the hairs. In the first place, it is only the peculiar short barbed hairs which will produce the dermatitis when rubbed on the skin, although most of the other hairs are sharply barbed. Moreover, it was found that in various ways the nettling properties could be destroyed without modifying the structure of the hairs. This was accomplished by baking for one hour at 110^o C, by warming to 60^o C in distilled water, or by soaking in one per cent. or in one-tenth per cent. of potassium hydrate or sodium hydrate. The most significant part of his work was the demonstration of the fact that if the nettling hairs are mingled with blood, they immediately produce a change in the red corpuscles. These at once become coarsely crenated, and the roleaux are broken up in the vicinity of the hair (fig. 37_b_). The corpuscles decrease in size, the coarse crenations are transformed into slender spines which rapidly disappear, leaving the corpuscles in the form of spheres, the light refraction of which contrasts them sharply with the normal corpuscles. The reaction always begins at the basal sharp point of the hair. It could not be produced by purely mechanical means, such as the mingling of minute particles of glass wool, the barbed hairs of a tussock moth, or the other coarser hairs of the brown-tail, with the blood.

The question of the source of the poison has been studied in our laboratory by Miss Cornelia Kephart. She first confirmed Dr. Tyzzer's general results and then studied carefully fixed specimens of the larvae to determine the distribution of the hairs and their relation to the underlying tissues.

The poison hairs (fig. 37), are found on the subdorsal and lateral tubercles (fig. 38), in bunches of from three to twelve on the minute papillae with which the tubercles are thickly covered. The underlying hypodermis is very greatly thickened, the cells being three or four times the length of the ordinary hypodermal cells and being closely crowded together. Instead of a pore canal through the cuticula for each individual hair, there is a single pore for each papillae on a tubercle, all the hairs of the papilla being connected with the underlying cells through the same pore canal, (figs. 39 and 40).

The hypodermis of this region is of two distinct types of cells. First, there is a group of slender fusiform cells, one for each poison hair on the papilla, which are the trichogen, or hair-formative cells. They are crowded to one side and towards the basement membrane by a series of much larger, and more prominent cells (fig. 40), of which there is a single one for each papilla. These larger cells have a granular protoplasm with large nuclei and are obviously actively secreting. They are so characteristic in appearance as to leave no question but that they are the true poison glands.

Poisonous larvae of many other species have been reported from Europe and especially from the tropics but the above-mentioned species are the more important of those occurring in the United States and will serve as types. It should be noted in this connection that through some curious misunderstanding Goeldi (1913) has featured the larva of _Orgyia leucostigma_, the white-marked tussock moth, as the most important of the poisonous caterpillars of this country. Though there are occasional reports of irritation from its hairs such cases are rare and there is no evidence that there is any poison present. Indeed, subcutaneous implantation of the hairs leads to no poisoning, but merely to temporary irritation.

Occasionally, the hairs of certain species of caterpillars find lodgement in the conjunctiva, cornea, or iris of the eye of man and give rise to the condition known as _opthalmia nodosa_. The essential feature of this trouble is a nodular conjunctivitis which simulates tuberculosis of the conjunctiva and hence has been called _pseudo-tubercular_. It may be distinguished microscopically by the presence of the hairs.

Numerous cases of opthalmia nodosa are on record. Of those from this country, one of the most interesting is reported by de Schweinitz and Shumway (1904). It is that of a child of fifteen years whose eye had become inflamed owing to the presence of some foreign body. Downward and inward on the bulbar conjunctiva were a number of flattened, grayish-yellow nodules, between which was a marked congestion of the conjunctival and episcleral vessels (fig. 41_a_). Twenty-seven nodules could be differentiated, those directly in the center of the collection being somewhat confluent and assuming a crescentic and circular appearance. The nodules were excised and, on sectioning, were found to be composed of a layer of spindle cells and round cells, outside of which the tissue was condensed into a capsule. The interior consisted of epithelioid cells, between which was a considerable intercellular substance. Directly in the center of a certain number of nodules was found the section of a hair (fig. 41_b_). The evidence indicated that the injury had resulted from playing with caterpillars of one of the Arctiid moths, _Spilosoma virginica_. Other reported cases have been caused by the hairs of larvae of _Lasiocampa rubi_, _L. pini_, _Porthetria dispar_, _Psilura monacha_ and _Cnethocampa processionea_.

RELIEF FROM POISONING BY NETTLING LARVAE--The irritation from nettling larvae is often severe and, especially in regions where the brown-tail abounds, inquiries as to treatment arise. In general, it may be said that cooling lotions afford relief, and that scratching, with the possibilities of secondary infection, should be avoided, in so far as possible.

Among the remedies usually at hand, weak solutions of ammonia, or a paste of ordinary baking soda are helpful. Castellani and Chalmers recommend cleaning away the hairs by bathing the region with an alkaline lotion, such as two per cent solution of bicarbonate of soda, and then applying an ointment of ichthyol (10%).

In the brown-tail district, there are many proprietary remedies of which the best ones are essentially the following, as recommended by Kirkland (1907):

Carbolic acid 1/2 drachm.
Zinc oxide 1/2 oz.
Lime water 8 oz.

Shake thoroughly and rub well into the affected parts.

In some cases, and especially where there is danger of secondary infection, the use of a weak solution of creoline (one teaspoonful to a quart of water), is to be advised.

VESCICATING INSECTS AND THOSE POSSESSING OTHER POISONS IN THEIR BLOOD PLASMA

We have seen that certain forms, for example, the poisonous spiders, not only secrete a toxine in their poison glands, but that such a substance may be extracted from other parts of their body, or even their eggs. There are many insects which likewise possess a poisonous blood plasma. Such forms have been well designated by Taschenberg as _cryptotoxic_ ([Greek: kryptos] = hidden). We shall consider a few representative forms.

THE BLISTER BEETLES--Foremost among the cryptotoxic insects are the _Meloidae_ or "blister beetles," to which the well-known "Spanish fly" (fig. 42_a_), formerly very generally used in medical practice, belongs. The vescicating property is due to the presence in the blood plasma of a peculiar, volatile, crystalline substance known as _cantharidin_, which is especially abundant in the reproductive organs of the beetle. According to Kobert, the amount of this varies in different species from .4 or .5% to 2.57% of the dry weight of the beetle.

While blister beetles have been especially used for external application, they are also at times used internally as a stimulant and a diuretic. The powder or extract was formerly much in vogue as an aphrodisiac, and formed the essential constituent of various philters, or "love powders". It is now known that its effects on the reproductive organs appear primarily after the kidneys have been affected to such an extent as to endanger life, and that many cases of fatal poison have been due to its ignorant use.

There are many cases on record of poisoning and death due to internal use, and in some instances from merely external application. There are not rarely cases of poisoning of cattle from feeding on herbage bearing a large number of the beetles and authentic cases are known of human beings who have been poisoned by eating the flesh of such cattle. Kobert states that the beetles are not poisonous to birds but that the flesh of birds which have fed on them is poisonous to man, and that if the flesh of chickens or frogs which have fed on the cantharidin be fed to cats it causes in them the same symptoms as does the cantharidin.

Treatment of cases of cantharidin poison is a matter for a skilled physician. Until he can be obtained, emetics should be administered and these should be followed by white of egg in water. Oils should be avoided, as they hasten the absorption of the poison.

OTHER CRYPTOTOXIC INSECTS--Though the blister beetles are the best known of the insects with poisonous blood plasma, various others have been reported and we shall refer to a few of the best authenticated.

One of the most famous is the Chrysomelid beetle, _Diamphidia simplex_, the body fluids of whose larvae are used by certain South African bushmen as an arrow poison. Its action is due to the presence of a toxalbumin which exerts a haemolytic action on the blood, and produces inflammation of the subcutaneous connective tissue and mucous membranes. Death results from general paralysis. Krause (1907) has surmised that the active principle may be a bacterial toxin arising from decomposition of the tissues of the larva, but he presents no support of this view and it is opposed by all the available evidence.

In China, a bug, _Heuchis sanguinea_, belonging to the family Cicadidae, is used like the Meloidae, to produce blistering, and often causes poisoning. It has been assumed that its vescicating properties are due to cantharidin, but the presence of this substance has not been demonstrated.

Certain Aphididae contain a strongly irritating substance which produces, not merely on mucous membranes but on outer skin, a characteristic inflammation.

It has been frequently reported that the larvae of the European cabbage butterfly, _Pieris brassicae_, accidentally eaten by cows, horses, ducks, and other domestic animals, cause severe colic, attempts to vomit, paralysis of the hind legs, salivation, and stomatitis. On _postmortem_ there are to be found haemorrhagic gastro-enteritis, splenitis, and nephritis. Kobert has recently investigated the subject and has found a poisonous substance in the blood of not only the larvae but also the pupae.

FOOTNOTES:

[A] This is diametrically opposed to the findings of Bordas (1905) in the case of the European _Latrodectus 13-guttatus_, whose glands are "much larger than those of other spiders." From a considerable comparative study, we should also unhesitatingly make this statement regarding the glands of our American species, _L. mactans_.

[B] Dr. E. H. Coleman (Kellogg, 1915) has demonstrated its virulence by a series of experiments comparable with those of Kobert.

[C] According to Stiles, the species occurring in the Northwest which is commonly identified as _D. venustus_ should be called _D. andersoni_ (see footnote, chapter 12).

[D] It should be remembered that in all the higher Hymenoptera the first abdominal segment is fused with the thorax and that what is apparently the sixth segment is, in reality, the seventh.