Handbook of Medical Entomology

by William A. Riley; O. A. Johannsen

ARANEIDA OR SPIDERS

Of all the arthropods there are none which are more universally feared than are the spiders. It is commonly supposed that the majority, if not all the species are poisonous and that they are aggressive enemies of man and the higher animals, as well as of lower forms.

That they really secrete a poison may be readily inferred from the effect of their bite upon insects and other small forms. Moreover, the presence of definite and well-developed poison glands can easily be shown. They occur as a pair of pouches ([fig. 1]) lying within the cephalothorax and connected by a delicate duct with a pore on the claw of the chelicera, or so-called "mandible" on the convex surface of the claw in such a position that it is not plugged and closed by the flesh of the victim.

The glands may be demonstrated by slowly and carefully twisting off a chelicera and pushing aside the stumps of muscles at its base. By exercising care, the chitinous wall of the chelicera and its claw may be broken away and the duct traced from the gland to its outlet. The inner lining of the sac is constituted by a highly developed glandular epithelium, supported by a basement membrane of connective tissue and covered by a muscular layer, ([fig. 2]). The muscles, which are striated, are spirally arranged ([fig. 1]), and are doubtless under control of the spider, so that the amount of poison to be injected into a wound may be varied.

The poison itself, according to Kobert (1901), is a clear, colorless fluid, of oily consistency, acid reaction, and very bitter taste. After the spider has bitten two or three times, its supply is exhausted and therefore, as in the case of snakes, the poison of the bite decreases quickly with use, until it is null. To what extent the content of the poison sacs may contain blood serum or, at least, active principles of serum, in addition to a specific poison formed by the poison glands themselves, Kobert regards as an open question. He believes that the acid part of the poison, if really present, is formed by the glands and that, in the case of some spiders, the ferment-like, or better, active toxine, comes from the blood.

But there is a wide difference between a poison which may kill an insect and one which is harmful to men. Certain it is that there is no lack of popular belief and newspaper records of fatal cases, but the evidence regarding the possibility of fatal or even very serious results for man is most contradictory. For some years, we have attempted to trace the more circumstantial newspaper accounts, which have come to our notice, of injury by North American species. The results have served, mainly, to emphasize the straits to which reporters are sometimes driven when there is a dearth of news. The accounts are usually vague and lacking in any definite clue for locating the supposed victim. In the comparatively few cases where the patient, or his physician, could be located, there was either no claim that the injury was due to spider venom, or there was no evidence to support the belief. Rarely, there was evidence that a secondary blood poisoning, such as might be brought about by the prick of a pin, or by any mechanical injury, had followed the bite of a spider. Such instances have no bearing on the question of the venomous nature of these forms.

The extreme to which unreasonable fear of the bites of spiders influenced the popular mind was evidenced by the accepted explanation of the remarkable dancing mania, or tarantism, of Italy during the Middle Ages. This was a nervous disorder, supposed to be due to the bite of a spider, the European tarantula ([fig. 4]), though it was also, at times, attributed to the bite of the scorpion. In its typical form, it was characterized by so great a sensibility to music that under its influence the victims indulged in the wildest and most frenzied dancing, until they sank to the ground utterly exhausted and almost lifeless. The profuse perspiring resulting from these exertions was supposed to be the only efficacious remedy for the disease. Certain forms of music were regarded as of especial value in treating this tarantism, and hence the name of "tarantella" was applied to them. Our frontispiece, taken from Athanasius Kircher's Magnes sive de Arte Magnetica, 1643 ed., represents the most commonly implicated spider and illustrates some of what Fabre has aptly designated as "medical choreography."

The disease was, in reality, a form of hysteria, spreading by sympathy until whole communities were involved, and was paralleled by the outbreaks of the so-called St. Vitus's or St. John's dance, which swept Germany at about the same time ([fig. 5]). The evidence that the spider was the cause of the first is about as conclusive as is that of the demoniacal origin of the latter. The true explanation of the outbreaks is doubtless to be found in the depleted physical and mental condition of the people, resulting from the wars and the frightful plagues which devastated all Europe previous to, and during these times. An interesting discussion of these aspects of the question is to be found in Hecker.

So gross has been the exaggeration and so baseless the popular fear regarding spiders that entomologists have been inclined to discredit all accounts of serious injury from their bites. Not only have the most circumstantial of newspaper accounts proved to be without foundation but there are on record a number of cases where the bite of many of the commoner species have been intentionally provoked and where the effect has been insignificant. Some years ago the senior author personally experimented with a number of the largest of our northern species, and with unexpected results. The first surprise was that the spiders were very unwilling to bite and that it required a considerable effort to get them to attempt to do so. In the second place, most of those experimented with were unable to pierce the skin of the palm or the back of the hand, but had to be applied to the thin skin between the fingers before they were able to draw blood. Unfortunately, no special attempt was made to determine, at the time, the species experimented with, but among them were Theridion tepidariorum, Miranda aurantia (Argiopa), Metargiope trifasciata, Marxia stellata, Aranea trifolium, Misumena vatia, and Agelena nævia. In no case was the bite more severe than a pin prick and though in some cases the sensation seemed to last longer, it was probably due to the fact that the mind was intent upon the experiment.

Similar experiments were carried out by Blackwell (1855), who believed that in the case of insects bitten, death did not result any more promptly than it would have from a purely mechanical injury of equal extent. He was inclined to regard all accounts of serious injury to man as baseless. The question cannot be so summarily dismissed, and we shall now consider some of the groups which have been more explicitly implicated.

The Tarantulas.—In popular usage, the term "tarantula" is loosely applied to any one of a number of large spiders. The famous tarantulas of southern Europe, whose bites were supposed to cause the dancing mania, were Lycosidæ, or wolf-spiders. Though various species of this group were doubtless so designated, the one which seems to have been most implicated was Lycosa tarantula (L.), ([fig. 4]). On the other hand, in this country, though there are many Lycosidæ, the term "tarantula" has been applied to members of the superfamily Avicularoidea ([fig. 6]), including the bird-spiders.

Of the Old World Lycosidæ there is no doubt that several species were implicated as the supposed cause of the tarantism. In fact, as we have already noted, the blame was sometimes attached to a scorpion. However, there seems to be no doubt that most of the accounts refer to the spider known as Lycosa tarantula.

There is no need to enter into further details here regarding the supposed virulence of these forms, popular and the older medical literature abound in circumstantial accounts of the terrible effects of the bite. Fortunately, there is direct experimental evidence which bears on the question.

Fabre induced a common south European wolf-spider, Lycosa narbonensis, to bite the leg of a young sparrow, ready to leave the nest. The leg seemed paralyzed as a result of the bite, and though the bird seemed lively and clamored for food the next day, on the third day it died. A mole, bitten on the nose, succumbed after thirty-six hours. From these experiments Fabre seemed justified in his conclusion that the bite of this spider is not an accident which man can afford to treat lightly. Unfortunately, there is nothing in the experiments, or in the symptoms detailed, to exclude the probability that the death of the animals was the result of secondary infection.

As far back as 1693, as we learn from the valuable account of Kobert, (1901), the Italian physician, Sanguinetti allowed himself to be bitten on the arm by two tarantulas, in the presence of witnesses. The sensation was equivalent to that from an ant or a mosquito bite and there were no other phenomena the first day. On the second day the wound was inflamed and there was slight ulceration. It is clear that these later symptoms were due to a secondary infection. These experiments have been repeated by various observers, among whom may be mentioned Leon Dufour, Josef Erker and Heinzel, and with the similar conclusion that the bite of the Italian tarantula ordinarily causes no severe symptoms. In this conclusion, Kobert, though firmly convinced of the poisonous nature of some spiders, coincides. He also believes that striking symptoms may be simulated or artificially induced by patients in order to attract interest, or because they have been assured that the bite, under all circumstances, caused tarantism.

The so-called Russian tarantula, Trochosa singoriensis ([fig. 7]), is much larger than the Italian species, and is much feared. Kobert carried out a series of careful experiments with this species and his results have such an important bearing on the question of the venomous nature of the tarantula that we quote his summary. Experimenting first on nearly a hundred living specimens of Trochosa singoriensis from Crimea he says that:

"The tarantulas, no matter how often they were placed on the skin, handled, and irritated, could not be induced to bite either myself, the janitor, or the ordinary experimental animals. The objection that the tarantulas were weak and indifferent cannot stand, for as soon as I placed two of them on the shaved skin of a rabbit, instead of an attack on the animal, there began a furious battle between the two spiders, which did not cease until one of the two was killed."

"Since the spiders would not bite, I carefully ground up the fresh animals in physiological salt solution, preparing an extract which must have contained, in solution, all of the poisonous substance of their bodies. While in the case of Latrodectus, as we shall see, less than one specimen sufficed to yield an active extract, I have injected the filtered extract of six fresh Russian tarantulas, of which each one was much heavier than an average Latrodectus, subcutaneously and into the jugular vein of various cats without the animals dying or showing any special symptoms. On the basis of my experiments I can therefore only say that the quantity of the poison soluble in physiological salt solution, even when the spiders are perfectly fresh and well nourished, is very insignificant. That the poison of the Russian tarantula is not soluble in physiological salt solution, is exceedingly improbable. Moreover, I have prepared alcoholic extracts and was unable to find them active. Since the Russian spider exceeds the Italian in size and in intensity of the bite, it seems very improbable to me that the pharmacological test of the Italian tarantula would yield essentially other results than those from the Russian species."

To the Avicularoidea belong the largest and most formidable appearing of the spiders and it is not strange that in the New World they have fallen heir to the bad reputation, as well as to the name of the tarantula of Europe. In this country they occur only in the South or in the far West, but occasionally living specimens are brought to our northern ports in shipments of bananas and other tropical produce, and are the source of much alarm. It should be mentioned, however, that the large spider most frequently found under such circumstances is not a tarantula at all, but one of the Heteropodidæ, or giant crab-spiders, ([fig. 8]).

In spite of their prominence and the fear which they arouse there are few accurate data regarding these American tarantulas. It has often been shown experimentally that they can kill small birds and mammals, though it is doubtful if these form the normal prey of any of the species, as has been claimed. There is no question but that the mere mechanical injury which they may inflict, and the consequent chances of secondary infection, justify, in part, their bad reputation. In addition to the injury from their bite, it is claimed that the body hairs of several of the South American species are readily detached and are urticating.

Recently, Phisalix (1912) has made a study of the physiological effects of the venom of two Avicularoidea, Phormictopus carcerides Pocock, from Haiti and Cteniza sauvagei Rossi, from Corsica. The glands were removed aseptically and ground up with fine, sterilized sand in distilled water. The resultant liquid was somewhat viscid, colorless, and feebly alkaline. Injected into sparrows and mice the extract of Phormictopus proved very actively poisonous, that from a single spider being sufficient to kill ten sparrows or twenty mice. It manifested itself first and, above all, as a narcotic, slightly lowering the temperature and paralyzing the respiration. Muscular and cardiac weakening, loss of general sensibility, and the disappearance of reflexes did not occur until near the end. The extract from Cteniza was less active and, curiously enough, the comparative effect on sparrows and on mice was just reversed.

Spiders of the Genus Latrodectus.—While most of the popular accounts of evil effects from the bites of spiders will not stand investigation, it is a significant fact that, the world over, the best authenticated records refer to a group of small and comparatively insignificant spiders belonging to the genus Latrodectus, of the family Theridiidæ. The dread "Malmigniatte" of Corsica and South Europe, the "Karakurte" of southeastern Russia, the "Katipo" of New Zealand, the "Mena-vodi" and "Vancoho" of Madagascar, and our own Latrodectus mactans, all belong to this genus, and concerning all of these the most circumstantial accounts of their venomous nature are given. These accounts are not mere fantastic stories by uneducated natives but in many cases are reports from thoroughly trained medical men.

The symptoms produced are general, rather than local. As summarized by Kobert (1901) from a study of twenty-two cases treated in 1888, in the Kherson (Russia) Government Hospital and Berislaw (Kherson) District Hospital the typical case, aside from complications, exhibits the following symptoms. The victim suddenly feels the bite, like the sting of a bee. Swelling of the barely reddened spot seldom follows. The shooting pains, which quickly set in, are not manifested at the point of injury but localized at the joints of the lower limb and in the region of the hip. The severity of the pain forces the victim to the hospital, in spite of the fact that they otherwise have a great abhorrence of it. The patient is unable to reach the hospital afoot, or, at least, not without help, for there is usually inability to walk. The patient, even if he has ridden, reaches the hospital covered with cold sweat and continues to perspire for a considerable period. His expression indicates great suffering. The respiration may be somewhat dyspnœic, and a feeling of oppression in the region of the heart is common. There is great aversion to solid food, but increasing thirst for milk and tea. Retention of urine, and constipation occur. Cathartics and, at night, strong narcotics are desired. Warm baths give great relief. After three days, there is marked improvement and usually the patient is dismissed after the fifth. This summary of symptoms agrees well with other trustworthy records.

It would seem, then, that Riley and Howard (1889), who discussed a number of accounts in the entomological literature, were fully justified in their statement that "It must be admitted that certain spiders of the genus Latrodectus have the power to inflict poisonous bites, which may (probably exceptionally and depending upon exceptional conditions) bring about the death of a human being."

And yet, until recently the evidence bearing on the question has been most conflicting. The eminent arachnologist, Lucas, (1843) states that he himself, had been repeatedly bitten by the Malmigniatte without any bad effects. Dr. Marx, in 1890, gave before the Entomological Society of Washington, an account of a series of experiments to determine whether the bite of Latrodectus mactans is poisonous or not. He described the poison glands as remarkably small[A] and stated that he had introduced the poison in various ways into guinea-pigs and rabbits without obtaining any satisfactory results. Obviously, carefully conducted experiments with the supposed venom were needed and fortunately they have been carried out in the greatest detail by Kobert (1901).

This investigator pointed out that there were two factors which might account for the discrepancies in the earlier experiments. In the first place, the poison of spiders, as of snakes, might be so exhausted after two or three bites that further bites, following directly, might be without visible effect. Secondly, the application of the poison by means of the bite, is exceedingly inexact, since even after the most careful selection of the point of application, the poison might in one instance enter a little vein or lymph vessel, and in another case fail to do so. Besides, there would always remain an incalculable and very large amount externally, in the nonabsorptive epithelium. While all of these factors enter into the question of the effect of the bite in specific instances, they must be as nearly as possible obviated in considering the question of whether the spiders really secrete a venom harmful to man.

Kobert therefore sought to prepare extracts which would contain the active principles of the poison and which could be injected in definite quantities directly into the blood of the experimental animal. For this purpose various parts of the spiders were rubbed up in a mortar with distilled water, or physiological salt solution, allowed to stand for an hour, filtered, and then carefully washed, by adding water drop by drop for twenty-four hours. The filtrate and the wash-water were then united, well mixed and, if necessary, cleared by centrifuging or by exposure to cold. The mixture was again filtered, measured, and used, in part, for injection and, in part, for the determination of the organic materials.

Such an extract was prepared from the cephalothoraces of eight dried specimens of the Russian Latrodectus and three cubic centimeters of this, containing 4.29 mg. of organic material, were injected into the jugular vein of a cat weighing 2450 grams. The previously very active animal was paralyzed and lay in whatever position it was placed. The sensibility of the skin of the extremities and the rump was so reduced that there was no reaction from cutting or sticking. There quickly followed dyspnœa, convulsions, paralysis of the respiratory muscles and of the heart. In twenty-eight minutes the cat was dead, after having exhibited exactly the symptoms observed in severe cases of poisoning of man from the bite of this spider.

These experiments were continued on cats, dogs, guinea pigs and various other animals. Not only extracts from the cephalothorax, but from other parts of the body, from newly hatched spiders, and from the eggs were used and all showed a similar virulence. Every effort was made to avoid sources of error and the experiments, conducted by such a recognized authority in the field of toxicology, must be accepted as conclusively showing that this spider and, presumably, other species of the genus Latrodectus against which the clinical evidence is quite parallel, possess a poison which paralyzes the heart and central nervous system, with or without preliminary stimulus of the motor center. If the quantity of the poison which comes into direct contact with the blood is large, there may occur hæmolysis and thrombosis of the vessels.

On the other hand, check experiments were carried out, using similar extracts of many common European spiders of the genera Tegenaria, Drassus, Agelena, Eucharia and Argyroneta, as well as the Russian tarantula, Lycosa singoriensis. In no other case was the effect on experimental animals comparable to the Latrodectus extract.

Kobert concludes that in its chemical nature the poison is neither an alkaloid, nor a glycoside, nor an acid, but a toxalbumen, or poisonous enzyme which is very similar to certain other animal poisons, notably that of the scorpion.

The genus Latrodectus is represented in the United States by at least two species, L. mactans and L. geometricus. Concerning L. mactans there are very circumstantial accounts of serious injury and even death in man[B]. Latrodectus mactans is coal black, marked with red or yellow or both. It has eight eyes, which are dissimilar in color and are distinctly in front of the middle of the thorax, the lateral eyes of each side widely separate. The tarsi of the fourth pair of legs has a number of curved setæ in a single series. It has on the ventral side of its abdomen an hour-glass shaped spot. The full-grown female is about half an inch in length. Its globose abdomen is usually marked with one or more red spots dorsally along the middle line. The male is about half as long but has in addition to the dorsal spots, four pairs of stripes along the sides. Immature females resemble the male in coloring ([fig. 9]).

Regarding the distribution of Latrodectus mactans, Comstock states that: "Although it is essentially a Southern species, it occurs in Indiana, Ohio, Pennsylvania, New Hampshire, and doubtless other of the Northern States." L. geometricus has been reported from California.

Other Venomous Spiders—While conclusive evidence regarding the venomous nature of spiders is meager and relates almost wholly to that of the genus Latrodectus, the group is a large one and we are not justified in dismissing arbitrarily, all accounts of injury from their bites. Several species stand out as especially needing more detailed investigation.

Chiracanthium nutrix is a common European species of the family Clubionidæ, concerning which there is much conflicting testimony. Among the reports are two by distinguished scientists whose accounts of personal experiences cannot be ignored. A. Forel allowed a spider of this species to bite him and not only was the pain extreme, but the general symptoms were so severe that he had to be helped to his house. The distinguished arachnologist, Bertkau reports that he, himself, was bitten and that an extreme, burning pain spread almost instantaneously over the arm and into the breast. There were slight chills the same day and throbbing pain at the wound lasted for days. While this particular species is not found in the United States, there are two other representatives of the genus and it is possible that they possess the same properties. We are unaware of any direct experimental work on the poison.

Epeira diadema, of Europe, belongs to a wholly different group, that of the orb-weavers, but has long been reputed venomous. Kobert was able to prepare from it an extract whose effects were very similar to that prepared from Latrodectus, though feebler in its action. Under ordinary circumstances this spider is unable to pierce the skin of man and though Kobert's results seem conclusive, the spider is little to be feared.

Phidippus audax (P. tripunctatus) is one of our largest Attids, or jumping spiders. The late Dr. O. Lugger describes a case of severe poisoning from the bite of this spider and though details are lacking, it is quite possible that this and other large species of the same group, which stalk their prey, may possess a more active poison than that of web-building species.

Summary—It is clearly established that our common spiders are not to be feared and that the stories regarding their virulence are almost wholly without foundation. On the other hand, the chances of secondary infection from the bites of some of the more powerful species are not to be ignored.

Probably all species possess a toxin secreted by the poison gland, virulent for insects and other normal prey of the spiders, but with little or no effect on man.

There are a very few species, notably of the genus Latrodectus, and possibly including the European Chiracanthium nutrix and Epeira diadema, which possess, in addition, a toxalbumen derived from the general body tissue, which is of great virulence and may even cause death in man and the higher animals.

THE PEDIPALPIDA OR WHIP-SCORPIONS

The tailed whip-scorpions, belonging to the family Thelyphonidæ, are represented in the United States by the giant whip-scorpion Mastigoproctus giganteus ([fig. 10]), which is common in Florida, Texas and some other parts of the South. In Florida, it is locally known as the "grampus" or "mule-killer" and is very greatly feared. There is no evidence that these fears have any foundation, and Dr. Marx states that there is neither a poison gland nor a pore in the claw of the chelicera.

THE SCORPIONIDA, OR TRUE SCORPIONS

The true scorpions are widely distributed throughout warm countries and everywhere bear an evil reputation. According to Comstock (1912), about a score of species occur in the Southern United States. These are comparatively small forms but in the tropics members of this group may reach a length of seven or eight inches. They are pre-eminently predaceous forms, which lie hidden during the day and seek their prey by night.

The scorpions ([fig. 11]) possess large pedipalpi, terminated by strongly developed claws, or chelæ. They may be distinguished from all other Arachnids by the fact that the distinctly segmented abdomen is divided into a broad basal region of seven segments and a terminal, slender, tail-like division of five distinct segments.

The last segment of the abdomen, or telson, terminates in a ventrally-directed, sharp spine, and contains a pair of highly developed poison glands. These glands open by two small pores near the tip of the spine. Most of the species when running carry the tip of the abdomen bent upward over the back, and the prey, caught and held by the pedipalpi, is stung by inserting the spine of the telson and allowing it to remain for a time in the wound.

The glands themselves have been studied in Prionurus citrinus by Wilson (1904). He found that each gland is covered by a sheet of muscle on its mesal and dorsal aspects, which may be described as the compressor muscle. The muscle of each side is inserted by its edge along the ventral inner surface of the chitinous wall of the telson, close to the middle line, and by a broader insertion laterally. A layer of fine connective tissue completely envelops each gland and forms the basis upon which the secreting cells rest. The secreting epithelium is columnar; and apparently of three different types of cells.

1. The most numerous have the appearance of mucous cells, resembling the goblet cells of columnar mucous membranes. The nucleus, surrounded by a small quantity of protoplasm staining with hæmatoxylin, lies close to the base of the cell.

2. Cells present in considerable numbers, the peripheral portions of which are filled with very numerous fine granules, staining with acid dyes such as methyl orange.

3. Cells few in number, filled with very large granules, or irregular masses of a substance staining with hæmatoxylin.

The poison, according to Kobert (1893), is a limpid, acid-reacting fluid, soluble in water but insoluble in absolute alcohol and ether. There are few data relative to its chemical nature. Wilson (1901) states that a common Egyptian species, Buthus quinquestriatus, has a specific gravity of 1.092, and contains 20.3% of solids and 8.4% ash.

The venom of different species appears to differ not only quantitatively but qualitatively. The effects of the bite of the smaller species of the Southern United States may be painful but there is no satisfactory evidence that it is ever fatal. On the other hand, certain tropical species are exceedingly virulent and cases of death of man from the bite are common.

In the case of Buthus quinquestriatus, Wilson (1904) found the symptoms in animals to be hypersecretion, salivation and lachrymation, especially marked, convulsions followed by prolonged muscular spasm; death from asphyxia. The temperature shows a slight, rarely considerable, rise. Rapid and considerable increase of blood-pressure (observed in dogs) is followed by a gradual fall with slowing of the heart-beat. The coagulability of the blood is not affected.

An interesting phase of Wilson's work was the experiments on desert mammals. The condition under which these animals exist must frequently bring them in contact with scorpions, and he found that they possess a degree of immunity to the venom sufficient at least to protect them from the fatal effects of the sting.

As far as concerns its effect on man, Wilson found that much depended upon the age. As high as 60 per cent of the cases of children under five, resulted fatally. Caroroz (1865), states that in a Mexican state of 15,000 inhabitants, the scorpions were so abundant and so much feared that the authorities offered a bounty for their destruction. A result was a large number of fatalities, over two hundred per year. Most of the victims were children who had attempted to collect the scorpions.

The treatment usually employed in the case of bites by the more poisonous forms is similar to that for the bite of venomous snakes. First, a tight ligature is applied above the wound so as to stop the flow of blood and lymph from that region. The wound is then freely excised and treated with a strong solution of permanganate of potash, or with lead and opium lotion.

In recent years there have been many attempts to prepare an antivenom, or antiserum comparable to what has been used so effectively in the case of snake bites. The most promising of these is that of Todd (1909), produced by the immunization of suitable animals. This antivenom proved capable of neutralizing the venom when mixed in vitro and also acts both prophylactically and curatively in animals. Employed curatively in man, it appears to have a very marked effect on the intense pain following the sting, and the evidence so far indicates that its prompt use greatly reduces the chance of fatal results.

THE SOLPUGIDA, OR SOLPUGIDS

The Solpugida are peculiar spider-like forms which are distinguished from nearly all other arachnids by the fact that they possess no true cephalothorax, the last two leg-bearing segments being distinct, resembling those of the abdomen in this respect. The first pair of legs is not used in locomotion but seemingly functions as a second pair of pedipalpi. [Figure 12] illustrates the striking peculiarities of the group. They are primarily desert forms and occur in the warm zones of all countries. Of the two hundred or more species, Comstock lists twelve as occurring in our fauna. These occur primarily in the southwest.

The Solpugida have long borne a bad reputation and, regarding virulence, have been classed with the scorpions. Among the effects of their bites have been described painful swelling, gangrene, loss of speech, cramps, delirium, unconsciousness and even death. Opposed to the numerous loose accounts of poisoning, there are a number of careful records by physicians and zoölogists which indicate clearly that the effects are local and though they may be severe, they show not the slightest symptom of direct poisoning.

More important in the consideration of the question is the fact that there are neither poison glands nor pores in the fangs for the exit of any poisonous secretion. This is the testimony of a number of prominent zoölogists, among whom is Dr. A. Walter, who wrote to Kobert at length on the subject and whose conclusions are presented by him.

However, it should be noted that the fangs are very powerful and are used in such a manner that they may inflict especially severe wounds. Thus, there may be more opportunity for secondary infection than is usual in the case of insect wounds.

The treatment of the bite of the Solpugida is, therefore, a matter of preventing infection. The wound should be allowed to bleed freely and then washed out with a 1:3000 solution of corrosive sublimate, and, if severe, a wet dressing of this should be applied. If infection takes place, it should be treated in the usual manner, regardless of its origin.

THE ACARINA, OR MITES AND TICKS

A number of the parasitic Acarina evidently secrete a specific poison, presumably carried by the saliva, but in most cases its effect on man is insignificant. There is an abundant literature dealing with the poisonous effect of the bite of these forms, especially the ticks, but until recently it has been confused by failure to recognize that various species may transmit diseases of man, rather than produce injury through direct poisoning. We shall therefore discuss the Acarina more especially in subsequent chapters, dealing with parasitism and with disease transmission.

Nevertheless, after the evidence is sifted, there can be no doubt that the bites of certain ticks may occasionally be followed by a direct poisoning, which may be either local or general in its effects. Nuttall (1908) was unable to determine the cause of the toxic effect, for, in Argas persicus, the species most often implicated, he failed to get the slightest local or general effect on experimental animals, from the injection of an emulsion prepared by crushing three of the ticks.

It seems clearly established that the bite of certain ticks may cause a temporary paralysis, or even complete paralysis, involving the organs of respiration or the heart, and causing death. In 1912, Dr. I. U. Temple, of Pendleton, Oregon, reported several cases of what he called "acute ascending paralysis" associated with the occurrence of ticks on the head or the back of the neck. A typical severe case was that of a six year old child, who had retired in her usual normal health. The following morning upon arising she was unable to stand on her feet. She exhibited paralysis extending to the knees, slight temperature, no pain, sensory nerves normal, motor nerves completely paralyzed, reflexes absent. The following day the paralysis had extended to the upper limbs, and before night of the third day the nerves of the throat (hypoglossal) were affected. The thorax and larynx were involved, breathing was labored, she was unable to swallow liquids, phonation was impossible and she could only make low, guttural sounds. At this stage, two ticks, fully distended with blood, were found over the junction of the spinal column with the occipital bones in the hollow depression. They were removed by the application of undiluted creoline. Though the child's life was despaired of, by the following morning she was very much improved. By evening she was able to speak. The paralysis gradually receded, remaining longest in the feet, and at the end of one week the patient was able to go home.

There was some doubt as to the exact species of tick implicated in the cases which Dr. Temple reported, although the evidence pointed strongly to Dermacentor venustus.[C] Somewhat later, Hadwen (1913) reported that "tick paralysis" occurs in British Columbia, where it affects not only man, but sheep and probably other animals. It is caused by the bites of Dermacentor venustus and was experimentally produced in lambs and a dog (Hadwen and Nuttall, 1913). It is only when the tick begins to engorge or feed rapidly, some days after it has become attached, that its saliva produces pathogenic effects.

Ulceration following tick bite is not uncommon. In many of the instances it is due to the file-like hypostome, with its recurved teeth, being left in the wound when the tick is forcibly pulled off.

THE MYRIAPODA, OR CENTIPEDES AND MILLIPEDES

The old class, Myriapoda includes the Diplopoda, or millipedes, and the Chilopoda, or centipedes. The present tendency is to raise these groups to the rank of classes.