Handbook of Medical Entomology Part 3

The millipedes are inoffensive and harmless. _Julus terrestris_, and related species, when irritated pour out over the entire body a yellowish secretion which escapes from cutaneous glands. It is volatile, with a pungent odor, and Phisalix (1900) has shown that it is an active poison when injected into the blood of experimental animals. This, however, does not ent.i.tle them to be considered as poisonous arthropods, in the sense of this chapter, any more than the toad can be considered poisonous to man because it secretes a venom from its cutaneous glands.

The Chilopoda

[Ill.u.s.tration: 14. Two common centipedes.

(_a_) Lithobius forficatus. After Comstock.

(_b_) Scutigera forceps. Natural size; after Howard.]

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, h.o.m.ogeneous, 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.

[Ill.u.s.tration: 15. Mandible of Scolopendra cingulata showing venom gland. After Dubosq.]

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.

THE HEXAPODA OR TRUE INSECTS

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 b.u.t.terflies 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 circ.u.mstances, 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.

PIERCING OR BITING INSECTS POISONOUS TO MAN

HEMIPTERA

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 ill.u.s.tration (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 maxillae are enclosed. The mandibles are more or less deeply serrate, depending on the species concerned.

[Ill.u.s.tration: 16. Beak of hemipteron.]

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 _Fulgoridae_ 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).

[Ill.u.s.tration: 17. Salivary glands of Notonecta maculata. After Bugnion and Popoff.]

[Ill.u.s.tration: 18. Pharyngeal syringe or salivary pump of Fulgora maculata. After Bugnion and Popoff.]

[Ill.u.s.tration: 19. Heteroptera, (_a_) Melanolestes picipes; (_b_) Notonecta undulata; (_c_, _d_) Aradus robustus (_c_) adult, (_d_) nymph, much enlarged; (_e_) Arilus cristatus; (_f_) Belostoma americana; (_g_) Nabis (Coriscus) subcoleoptratus, enlarged; (_h_) Cimex lectularius, (_i_) Oeciacus vicarius, much enlarged; (_j_) Lyctocoris fitchii, much enlarged. After Lugger.]

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 NOTONECTIDae, or _back swimmers_, (fig. 19_b_) 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 "Wa.s.serbienen."

The BELOSTOMATIDae, or _giant water bugs_, (fig. 19_f_) 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 sophagus. On each side of the sophagus 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 h.o.m.ologues 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 Belostomatidae 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 woodp.e.c.k.e.r, 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.

[Ill.u.s.tration: 20. Reduvius (Opsictus) personatus. (2).]

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.

[Ill.u.s.tration: 21. (_a_) Reduvius personatus, nymph. Photograph by M. V.

S.]

The REDUVIIDae, or _a.s.sa.s.sin-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.

[Ill.u.s.tration: 21. (_b_) Reduvius personatus, adult (2) Photograph by M. V. S.]

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."

[Ill.u.s.tration: 22. Rasahus biguttatus. (2). After Howard.]

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 Reduviidae which, with greater or less frequency pierce the skin of human beings. These are _Opsicoetes personatus_, _Melanolestes picipes_, _Coriscus subcoleoptratus_ (fig. 19_g_), _Rasahus thoracicus_, _Rasahus biguttatus_ (fig. 22), _Conorhinus sanguisugus_ (fig. 71), and _Melanolestes abdominalis_ (fig. 23).