The Chilopoda, or centipedes (fig. 14), unlike the millipedes, are predaceous forms, and possess well developed poison glands for killing their prey. These glands are at the base of the first pair of legs (fig. 15), which are bent forward so as to be used in holding their prey. The legs terminate in a powerful claw, at the tip of which is the outlet of the poison glands.
The poison is a limpid, homogeneous, slightly acid fluid, which precipitates in distilled water. Briot (1904) extracted it from the glands of Scolopendra morsitans, a species common in central France, and found that it was actively venomous for the ordinary experimental animals. A rabbit of two kilograms weight received an injection of three cubic centimeters in the vein of the ear and died in a minute. A white rat, weighing forty-eight grams, received one and a half cubic centimeters in the hind leg. There was an almost immediate paralysis of the leg and marked necrosis of the tissues.
As for the effect on man, there is little foundation for the fear with which centipedes are regarded. Our native species produce, at most, local symptoms,—sometimes severe local pain and swelling,—but there is no authentic record of fatal results. In the tropics, some of the species attain a large size, Scolopendra gigantea reaching a length of nearly a foot. These forms are justly feared, and there is good evidence that death sometimes, though rarely, results from their bite.
One of the most careful accounts of death from the sting of the scorpion is that of Linnell, (1914), which relates to a comparatively small Malayan species, unfortunately undetermined. The patient, a coolie, aged twenty, was admitted to a hospital after having been stung two days previously on the left heel. For cure, the other coolies had made him eat the head of the scorpion. On admission, the patient complained of "things creeping all over the body". Temp. 102.8°. On the fourth day he had paralysis of the legs, and on the fifth day motor paralysis to the umbilicus, sensation being unaltered. On the sixth day there was retention of the urine and on the ninth day (first test after third day) sugar was present. On the thirteenth day the patient became comatose, but could be roused to eat and drink. The temperature on the following day fell below 95° and the patient was still comatose. Death fifteenth day.
Examination of the spinal (lumbar) cord showed acute disseminated myelitis. In one part there was an acute destruction of the anterior horn and an infiltration of round cells. In another portion Clarke's column had been destroyed. The perivascular sheaths were crowded with small round cells and the meninges were congested. Some of the cells of the anterior horn were swollen and the nuclei eccentric; chromatolysis had occurred in many of them.
As for treatment, Castellani and Chalmers (1910), recommend bathing the part well with a solution of ammonia (one in five, or one in ten). After bathing, apply a dressing of the same alkali or, if there is much swelling and redness, an ice-bag. If necessary, hypodermic injections of morphine may be given to relieve the pain. At a later period fomentations may be required to reduce the local inflammation.
There are a number of Hexapoda, or true insects, which are, in one way or another, poisonous to man. These belong primarily to the orders Hemiptera, or true bugs; Lepidoptera, or butterflies and moths (larval forms); Diptera, or flies; Coleoptera, or beetles; and Hymenoptera, or ants, bees, and wasps. There are various ways in which they may be poisonous.
1. Piercing or biting forms may inject an irritating or poisonous saliva into the wound caused by their mouth-parts.
2. Stinging forms may inject a poison, from glands at the caudal end of the abdomen, into wounds produced by a specially modified ovipositer, the sting.
3. Nettling properties may be possessed by the hairs of the insect.
4. Vescicating, or poisonous blood plasma, or body fluids are known to exist in a large number of species and may, under exceptional circumstances, affect man.
For convenience of discussion, we shall consider poisonous insects under these various headings. In this, as in the preceding discussion, no attempt will be made to give an exhaustive list of the poisonous forms. Typical instances will be selected and these will be chosen largely from North American species.
Several families of the true bugs include forms which, while normally inoffensive, are capable of inflicting painful wounds on man. In these, as in all of the Hemiptera, the mouth-parts are modified to form an organ for piercing and sucking. This is well shown by the accompanying illustration (fig. 16).
The upper lip, or labrum, is much reduced and immovable, the lower lip, or labium, is elongated to form a jointed sheath, within which the lance-like mandibles and maxillæ are enclosed. The mandibles are more or less deeply serrate, depending on the species concerned.
The poison is elaborated by the salivary glands, excepting, possibly, in Belostoma where Locy is inclined to believe that it is secreted by the maxillary glands. The salivary glands of the Hemiptera have been the subject of much study but the most recent, comprehensive work has been done by Bugnion and Popoff, (1908 and 1910) to whose text the reader is referred for details.
The Hemiptera have two pairs of salivary glands: the primary gland, of which the efferent duct leads to the salivary syringe, and the accessory gland, of which the very long and flexuous duct empties into the primary duct at its point of insertion. Thus, when one observes the isolated primary gland it appears as though it had efferent ducts inserted at the same point. In Nepa and the Fulgoridæ there are two accessory glands and therefore apparently three ducts at the same point on the primary gland. The ensemble differs greatly in appearance in different species but we shall show here Bugnion and Popoff's figure of the apparatus of Notonecta maculata, a species capable of inflicting a painful bite on man (fig. 17).
Accessory to the salivary apparatus there is on the ventral side of the head, underneath the pharynx, a peculiar organ which the Germans have called the "Wanzenspritze," or syringe. The accompanying figure of the structure in Fulgora maculata (fig. 18) shows its relation to the ducts of the salivary glands and to the beak. It is made up of a dilatation forming the body of the pump, in which there is a chitinous piston. Attached to the piston is a strong retractor muscle. The function of the salivary pump is to suck up the saliva from the salivary ducts and to force it out through the beak.
Of the Hemiptera reported as attacking man, we shall consider briefly the forms most frequently noted.
The Notonectidæ, or back swimmers, (fig. 19b) are small, aquatic bugs that differ from all others in that they always swim on their backs. They are predaceous; feeding on insects and other small forms. When handled carelessly they are able to inflict a painful bite, which is sometimes as severe as the sting of a bee. In fact, they are known in Germany as "Wasserbienen."
The Belostomatidæ, or giant water bugs, (fig. 19f) include the largest living Hemiptera. They are attracted to lights and on account of the large numbers which swarm about the electric street lamps in some localities they have received the popular name "electric light bugs." Our largest representatives in the northern United States belong to the two genera Belostoma and Banacus, distinguished from each other by the fact that Belostoma has a groove on the under side of the femur of the front leg, for the reception of the tibia.
The salivary glands of Belostoma were figured by Leidy (1847) and later were studied in more detail by Locy (1884). There are two pairs of the glands, those of one pair being long and extending back as far as the beginning of the abdomen, while the others are about one-fourth as long. They lie on either side of the œsophagus. On each side of the œsophagus there is a slender tube with a sigmoid swelling which may serve as a poison reservoir. In addition to this salivary system, there is a pair of very prominent glands on the ventral side of the head, opening just above the base of the beak. These Locy has called the "cephalic glands" and he suggests that they are the source of the poison. They are the homologues of the maxillary glands described for other Hemiptera, and it is by no means clear that they are concerned with the production of venom. It seems more probable that in Belostoma, as in other Hemiptera, it is produced by the salivary glands, though the question is an open one.
The Belostomatidæ feed not only on insects, but on small frogs, fish, salamanders and the like. Matheson (1907) has recorded the killing of a good-sized bird by Belostoma americana. A woodpecker, or flicker, was heard to utter cries of distress, and fluttered and fell from a tree. On examination it was found that a bug of this species had inserted its beak into the back part of the skull and was apparently busily engaged in sucking the blood or brains of the bird. Various species of Belostoma have been cited as causing painful bites in man. We can testify from personal experience that the bite of Belostoma americana may almost immediately cause severe, shooting pains that may extend throughout the arm and that they may be felt for several days.
Relief from the pain may be obtained by the use of dilute ammonia, or a menthol ointment. In the not uncommon case of secondary infection the usual treatment for that should be adopted.
The Reduviidæ, or assassin-bugs are capable of inflicting very painful wounds, as most collectors of Hemiptera know to their sorrow. Some species are frequently to be found in houses and outhouses and Dr. Howard suggests that many of the stories of painful spider bites relate to the attack of these forms.
An interesting psychological study was afforded in the summer of 1899, by the "kissing-bug" scare which swept over the country. It was reported in the daily papers that a new and deadly bug had made its appearance, which had the unpleasant habit of choosing the lips or cheeks for its point of attack on man. So widespread were the stories regarding this supposedly new insect that station entomologists all over the country began to receive suspected specimens for identification. At Cornell there were received, among others, specimens of stone-flies, may-flies and even small moths, with inquiries as to whether they were "kissing-bugs."
Dr. L. O. Howard has shown that the scare had its origin in newspaper reports of some instances of bites by either Melanolestes picipes (fig. 19a) or Opsicoetes personatus (fig. 20), in the vicinity of Washington, D. C. He then discusses in considerable detail the more prominent of the Reduviidæ which, with greater or less frequency pierce the skin of human beings. These are Opsicoetes personatus, Melanolestes picipes, Coriscus subcoleoptratus (fig. 19g), Rasahus thoracicus, Rasahus biguttatus (fig. 22), Conorhinus sanguisugus (fig. 71), and C. abdominalis (fig. 23).
One of the most interesting of these species is Reduvius personatus, (= Opsicœtus personatus), which is popularly known as the "masked bed-bug hunter." It owes this name to the fact that the immature nymphs (fig. 21) have their bodies and legs completely covered by dust and lint, and that they are supposed to prey upon bed-bugs. LeConte is quoted by Howard as stating that "This species is remarkable for the intense pain caused by its bite. I do not know whether it ever willingly plunges its rostrum into any person, but when caught, or unskilfully handled it always stings. In this case the pain is almost equal to the bite of a snake, and the swelling and irritation which result from it will sometimes last for a week."
A species which very commonly attacks man is Conorhinus sanguisugus, the so-called "big bed-bug" of the south and southern United States. It is frequently found in houses and is known to inflict an exceedingly painful bite. As in the case of a number of other predaceous Hemiptera, the salivary glands of these forms are highly developed. The effect of the bite on their prey and, as Marlatt has pointed out, the constant and uniform character of the symptoms in nearly all cases of bites in man, clearly indicate that their saliva contains a specific substance. No satisfactory studies of the secretions have been made. On the other hand, Dr. Howard is doubtless right in maintaining that the very serious results which sometimes follow the bite are due to the introduction of extraneous poison germs. This is borne out by the symptoms of most of the cases cited in literature and also by the fact that treatment with corrosive sublimate, locally applied to the wound, has yielded favorable results.
Other Hemiptera Reported as Poisonous to Man—A large number of other Hemiptera have been reported as attacking man. Of these, there are several species of Lygæidæ, Coreidæ, and Capsidæ. Of the latter, Lygus pratensis, the tarnished plant-bug, is reported by Professor Crosby as sucking blood. Orthotylus flavosparsus is another Capsid which has been implicated. Empoasca mali and Platymetopius acutus of the Jassidæ have also been reported as having similar habits.
Whenever the periodical cicada or "seventeen-year locust" becomes abundant, the newspapers contain accounts of serious results from its bites. The senior author has made scores of attempts to induce this species to bite and only once successfully. At that time the bite was in no wise more severe than a pin-prick. A student in our department reports a similar experience. There is no case on record which bears evidence of being worthy of any credence, whatsoever.
Under the heading of poisonous Hemiptera we might consider the bed-bugs and the lice. These will be discussed later, as parasites and as carriers of disease, and therefore need only be mentioned here.
Several species of blood-sucking Diptera undoubtedly secrete a saliva possessing poisonous properties. Chief among these are the Culicidæ, or mosquitoes, and the Simuliidæ, or black-flies. As we shall consider these forms in detail under the heading of parasitic species and insects transmitting disease, we shall discuss here only the poison of the mosquitoes.
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 Spirochæta, 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 œsophageal 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 œsophageal 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 œsophageal 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.
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° 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, œdema, and hyperæmia.
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 œdema 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 Camponotinæ, 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° 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.
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 larvæ of certain Lepidoptera.