Part 5

This insect has been mentioned several times in entomological literature. The first reference to its bite probably was made by Townend Glover in the Annual Report of the Commissioner of Agriculture for 1875 (page 130). In Maryland, he states, _M. picipes_ is found under stones, moss, logs of wood, etc., and is capable of inflicting a severe wound with its rostrum or piercer. In 1888 Dr. Lintner, in his Fourth Report as State Entomologist of New York (page 110), quotes from a correspondent in Natchez, Miss., concerning this insect: "I send a specimen of a fly not known to us here. A few days ago it punctured the finger of my wife, inflicting a painful sting. The swelling was rapid, and for several days the wound was quite annoying." Until recent years this insect has not been known to the writer as occurring in houses with any degree of frequency. In May, 1895, however, I received a specimen from an esteemed correspondent--Dr. J. M. Shaffer, of Keokuk, Iowa--together with a letter written on May 7th, in which the statement was made that four specimens flew into his window the night before. The insect, therefore, is attracted to light or is becoming attracted to light, is a night-flier, and enters houses through open windows. Among the several cases coming under the writer's observation of bites by this insect, one has been reported by the well-known entomologist Mr. Charles Dury, of Cincinnati, Ohio, in which this species (_M. picipes_) bit a man on the back of the hand, making a bad sore. In another case, where the insect was brought for our determination and proved to be this species, the bite was upon the cheek, and the swelling was said to be great, but with little pain. In a third case, occurring at Holland, S. C., the symptoms were more serious. The patient was bitten upon the end of the middle finger, and stated that the first paroxysm of pain was about like that resulting from a hornet or a bee sting, but almost immediately it grew ten times more painful, with a feeling of weakness followed by vomiting. The pain was felt to shoot up the arm to the under jaw, and the sickness lasted for a number of days. A fourth case, at Fort Bliss, Texas, is interesting as having occurred in bed. The patient was bitten on the hand, with very painful results and bad swelling.

The third of the Eastern species, _Coriscus subcoleoptratus_, is said by Uhler to have a general distribution in the Northern States, and is like the species immediately preceding a native insect. There is no record of any bite by this species, and it is introduced here for the reason that it attracted the writer's attention crawling upon the walls of an earth closet in Greene County, New York, where on one occasion it bit him between the fingers. The pain was sharp, like the prick of a pin, but only a faint swelling followed, and no further inconvenience. The insect is mentioned, however, for the reason that, occurring in such situations, it is one of the forms which are liable to carry pathogenic bacteria.

There remain for consideration the Southern and Western forms--_Rasatus thoracicus_ and _R. biguttatus_, and _Conorhinus sanguisugus_.

The two-spotted corsair, as _Rasatus biguttatus_ is popularly termed, is said by Riley to be found frequently in houses in the Southern States, and to prey upon bedbugs. Lintner, referring to the fact that it preys upon bedbugs, says: "It evidently delights in human blood, but prefers taking it at second hand." Dr. A. Davidson, formerly of Los Angeles, Cal., in an important paper entitled So-called Spider Bites and their Treatment, published in the Therapeutic Gazette of February 15, 1897, arrives at the conclusion that almost all of the so-called spider bites met with in southern California are produced by no spider at all, but by _Rasatus biguttatus_. The symptoms which he describes are as follows: "Next day the injured part shows a local cellulitis, with a central dark spot; around this spot there frequently appears a bullous vesicle about the size of a ten-cent piece, and filled with a dark grumous fluid; a small ulcer forms underneath the vesicle, the necrotic area being generally limited to the central part, while the surrounding tissues are more or less swollen and somewhat painful. In a few days, with rest and proper care, the swelling subsides, and in a week all traces of the cellulitis are usually gone. In some of the cases no vesicle forms at the point of injury, the formation probably depending on the constitutional vitality of the individual or the amount of poison introduced." The explanation of the severity of the wound suggested by Dr. Davidson, and in which the writer fully concurs with him, is not that the insect introduces any specific poison of its own, but that the poison introduced is probably accidental and contains the ordinary putrefactive germs which may adhere to its proboscis. Dr. Davidson's treatment was corrosive sublimate--1 to 500 or 1 to 1,000--locally applied to the wound, keeping the necrotic part bathed in the solution. The results have in all cases been favorable. Uhler gives the distribution of _R. biguttatus_ as Arizona, Texas, Panama, Pará, Cuba, Louisiana, West Virginia, and California. After a careful study of the material in the United States National Museum, Mr. Heidemann has decided that the specimens of _Rasatus_ from the southeastern part of the country are in reality Say's _R. biguttatus_, while those from the Southwestern States belong to a distinct species answering more fully, with slight exceptions, to the description of Stal's _Rasatus thoracicus_. The writer has recently received a large series of _R. thoracicus_ from Mr. H. Brown, of Tucson, Arizona, and had a disagreeable experience with the same species in April, 1898, at San José de Guaymas, in the State of Sonora, Mexico. He had not seen the insect alive before, and was sitting at the supper table with his host--a ranchero of cosmopolitan language. One of the bugs, attracted by the light, flew in with a buzz and flopped down on the table. The writer's entomological instinct led him to reach out for it, and was warned by his host in the remarkable sentence comprising words derived from three distinct languages: "Guardez, guardez! Zat animalito sting like ze dev!" But it was too late; the writer had been stung on the forefinger, with painful results. Fortunately, however, the insect's beak must have been clean, and no great swelling or long inconvenience ensued.

Perhaps the best known of any of the species mentioned in our list is the blood-sucking cone-nose (_Conorhinus sanguisugus_). This ferocious insect belongs to a genus which has several representatives in the United States, all, however, confined to the South or West. _C. rubro-fasciatus_ and _C. variegatus_, as well as _C. sanguisugus_, are given the general geographical distribution of "Southern States." _C. dimidiatus_ and _C. maculipennis_ are Mexican forms, while _C. gerstaeckeri_ occurs in the Western States. The more recently described species, _C. protractus_ Uhl., has been taken at Los Angeles, Cal.; Dragoon, Ariz.; and Salt Lake City, Utah. All of these insects are blood-suckers, and do not hesitate to attack animals. Le Conte, in his original description of _C. sanguisugus_,[5] adds a most significant paragraph or two which, as it has not been quoted of late, will be especially appropriate here: "This insect, equally with the former" (see above), "inflicts a most painful wound. It is remarkable also for sucking the blood of mammals, particularly of children. I have known its bite followed by very serious consequences, the patient not recovering from its effects for nearly a year. The many relations which we have of spider bites frequently proving fatal have no doubt arisen from the stings of these insects or others of the same genera. When the disease called spider bite is not an anthrax or carbuncle it is undoubtedly occasioned by the bite of an insect--by no means however, of a spider. Among the many species of _Araneidæ_ which we have in the United States I have never seen one capable of inflicting the slightest wound. Ignorant persons may easily mistake a _Cimex_ for a spider. I have known a physician who sent to me the fragments of a large ant, which he supposed was a spider, that came out of his grandchild's head." The fact that Le Conte was himself a physician, having graduated from the College of Physicians and Surgeons in 1846, thus having been nine years in practice at the time, renders this statement all the more significant. The life history and habits of _C. sanguisugus_ have been so well written up by my assistant, Mr. Marlatt, in Bulletin No. 4, New Series, of the Division of Entomology, United States Department of Agriculture, that it is not necessary to enter upon them here. The point made by Marlatt--that the constant and uniform character of the symptoms in nearly all cases of bites by this insect indicate that there is a specific poison connected with the bite--deserves consideration, but there can be no doubt that the very serious results which sometimes follow the bite are due to the introduction of extraneous poison germs. The late Mr. J. B. Lembert, of Yosemite, Cal., noticed particularly that the species of _Conorhinus_ occurring upon the Pacific coast is attracted by carrion. Professor Toumey, of Tucson, Arizona, shows how a woman broke out all over the body and limbs with red blotches and welts from a single sting on the shoulders. Specimens of _C. sanguisugus_ received in July, 1899, from Mayersville, Miss., were accompanied by the statement--which is appropriate, in view of the fact that the newspapers have insisted that the "kissing bug" prefers the lip--that a friend of the writer was bitten on the lip, and that the effect was a burning pain, intense itching, and much swelling, lasting three or four days. The writer of the letter had been bitten upon the leg and arm, and his brother was bitten upon both feet and legs and on the arm, the symptoms being the same in all cases.

[5] Proceedings of the Academy of Natural Sciences of Philadelphia, vol. vii, p. 404 1854-'55.

More need hardly be said specifically concerning these biting bugs. The writer's conclusions are that a puncture by any one of them may be and frequently has been mistaken for a spider bite, and that nearly all reported spider-bite cases have had in reality this cause, that the so-called "kissing-bug" scare has been based upon certain undoubted cases of the bite of one or the other of them, but that other bites, including mosquitoes, with hysterical and nervous symptoms produced by the newspaper accounts, have aided in the general alarm. The case of Miss Larson, who died in August, 1898, as the result of a mosquito bite, at Mystic, Conn., is an instance which goes to show that no mysterious new insect need be looked for to explain occasional remarkable cases. One good result of the "kissing-bug" excitement will prove in the end to be that it will have relieved spiders from much unnecessary discredit.

THE MOSQUITO THEORY OF MALARIA.[6]

BY MAJOR RONALD ROSS.

I have the honor to address you, on completion of my term of special duty for the investigation of malaria, on the subject of the practical results as regard the prevention of the disease which may be expected to arise from my researches; and I trust that this letter may be submitted to the Government if the director general thinks fit.

[6] A report, published in Nature, from Major Ronald Ross to the Secretary to the Director General, Indian Medical Service, Simla. Dated Calcutta, February 16, 1899.

It has been shown in my reports to you that the parasites of malaria pass a stage of their existence in certain species of mosquitoes, by the bites of which they are inoculated into the blood of healthy men and birds. These observations have solved the problem--previously thought insolvable--of the mode of life of these parasites in external Nature.

My results have been accepted by Dr. Laveran, the discoverer of the parasites of malaria; by Dr. Manson, who elaborated the mosquito theory of malaria; by Dr. Nuttall, of the Hygienic Institute of Berlin, who has made a special study of the relations between insects and disease; and, I understand, by M. Metchnikoff, Director of the Laboratory of the Pasteur Institute in Paris. Lately, moreover, Dr. C. W. Daniels, of the Malaria Commission, who has been sent to study with me in Calcutta, has confirmed my observations in a special report to the Royal Society; while, lastly, Professor Grassi and Drs. Bignami and Bastianelli, of Rome, have been able, after receiving specimens and copies of my reports from me, to repeat my experiments in detail, and to follow two of the parasites of human malaria through all their stages in a species of mosquito called the _Anopheles claviger_.

It may therefore be finally accepted as a fact that malaria is communicated by the bites of some species of mosquito; and, to judge from the general laws governing the development of parasitic animals, such as the parasites of malaria, this is very probably the only way in which infection is acquired, in which opinion several distinguished men of science concur with me.

In considering this statement it is necessary to remember that it does not refer to the mere recurrences of fever to which people previously infected are often subject as the result of chill, fatigue, and so on. When I say that malaria is communicated by the bites of mosquitoes, I allude only to the original infection.

It is also necessary to guard against assertions to the effect that malaria is prevalent where mosquitoes and gnats do not exist. In my experience, when the facts come to be inquired into, such assertions are found to be untrue. Scientific research has now yielded so absolute a proof of the mosquito theory of malaria that hearsay evidence opposed to it can no longer carry any weight.

Hence it follows that, in order to eliminate malaria wholly or partly from a given locality, it is necessary only to exterminate the various species of insect which carry the infection. This will certainly remove the malaria to a large extent, and will almost certainly remove it altogether. It remains only to consider whether such a measure is practicable.

Theoretically the extermination of mosquitoes is a very simple matter. These insects are always hatched from aquatic larvæ or grubs which can live only in small stagnant collections of water, such as pots and tubs of water, garden cisterns, wells, ditches and drains, small ponds, half-dried water courses, and temporary pools of rain-water. So far as I have yet observed, the larvæ are seldom to be found in larger bodies of water, such as tanks, rice fields, streams, and rivers and lakes, because in such places they are devoured by minnows and other small fish. Nor have I ever seen any evidence in favor of the popular view that they breed in damp grass, dead leaves, and so on.

Hence, in order to get rid of these insects from a locality, it will suffice to empty out or drain away, or treat with certain chemicals, the small collections of water in which their larvæ must pass their existence.

But the practicability of this will depend on circumstances--especially, I think, on the species of mosquito with which we wish to deal. In my experience, different species select different habitations for their larvæ. Thus the common "brindled mosquitoes" breed almost entirely in pots and tubs of water; the common "gray mosquitoes" only in cisterns, ditches, and drains; while the rarer "spotted-winged mosquitoes" seem to choose only shallow rain-water puddles and ponds too large to dry up under a week or more, and too small or too foul and stagnant for minnows.

Hence the larvæ of the first two varieties are found in large numbers round almost all human dwellings in India; and, because their breeding grounds--namely, vessels of water, drains, and wells--are so numerous and are so frequently contained in private tenements, it will be almost impossible to exterminate them on a large scale.

On the other hand, spotted-winged mosquitoes are generally much more rare than the other two varieties. They do not appear to breed in wells, cisterns, and vessels of water, and therefore have no special connection with human habitations. In fact, it is usually a matter of some difficulty to obtain their larvæ. Small pools of any permanence--such as they require--are not common in most parts of India, except during the rains, and then pools of this kind are generally full of minnows which make short work of any mosquito larvæ they may find. In other words, the breeding grounds of the spotted-winged varieties seem to be so isolated and small that I think it may be possible to exterminate this species under certain circumstances.

The importance of these observations will be apparent when I add that hitherto the parasites of human malaria have been found only in spotted-winged mosquitoes--namely, in two species of them in India and in one species in Italy. As a result of very numerous experiments I think that the common brindled and gray mosquitoes are quite innocuous as regards human malaria--a fortunate circumstance for the human race in the tropics; and Professor Grassi seems to have come to the same conclusion as the result of his inquiries in Italy.

But I wish to be understood as writing with all due caution on these points. Up to the present our knowledge, both as regards the habits of the various species of mosquito and as regards the capacity of each for carrying malaria, is not complete. All I can now say is that if my anticipations be realized--if it be found that the malaria-bearing species of mosquito multiply only in small isolated collections of water which can easily be dissipated--we shall possess a simple mode of eliminating malaria from certain localities.

I limit this statement to certain localities only, because it is obvious that where the breeding pools are very numerous, as in water-logged country, or where the inhabitants are not sufficiently advanced to take the necessary precautions, we can scarcely expect the recent observations to be of much use--at least for some years to come. And this limitation must, I fear, exclude most of the rural areas in India.

Where, however, the breeding pools are not very numerous, and where there is anything approaching a competent sanitary establishment, we may, I think, hope to reap the benefit of these discoveries. And this should apply to the most crowded areas, such as those of cities, towns and cantonments, and also to tea, coffee, and indigo estates, and perhaps to military camps.

For instance, malaria causes an enormous amount of sickness among the poor in most Indian cities. Here the common species of mosquitoes breed in the precincts of almost all the houses, and can therefore scarcely be exterminated; but pools suitable for the spotted-winged varieties are comparatively scarce, being found only on vacant areas, ill-kept gardens, or beside roads in very exceptional positions where they can neither dry up quickly nor contain fish. Thus a single small puddle may supply the dangerous mosquitoes to several square miles containing a crowded population: if this be detected and drained off--which will generally cost only a very few rupees--we may expect malaria to vanish from that particular area.

The same considerations will apply to military cantonments and estates under cultivation. In many such malaria causes the bulk of the sickness, and may often, I think, originate from two or three small puddles of a few square yards in size. Thus in a malarious part of the cantonment of Secunderabad I found the larvæ of spotted-winged mosquitoes only after a long search in a single little pool which could be filled up with a few cart-loads of town rubbish.

In making these suggestions I do not wish to excite hopes which may ultimately prove to have been unfounded. We do not yet know all the dangerous species of mosquito, nor do we even possess an exhaustive knowledge of the haunts and habits of any one variety. I wish merely to indicate what, so far as I can see at present, may become a very simple means of eradicating malaria.

One thing may be said for certain. Where previously we have been unable to point out the exact origin of the malaria in a locality, and have thought that it rises from the soil generally, we now hope for much more precise knowledge regarding its source; and it will be contrary to experience if human ingenuity does not finally succeed in turning such information to practical account.

More than this, if the distinguishing characteristics of the malaria-bearing mosquitoes are sufficiently marked (if, for instance, they all have spotted wings), people forced to live or travel in malarious districts will ultimately come to recognize them and to take precautions against being bitten by them.

Before practical results can be reasonably looked for, however, we must find precisely--

(_a_) What species of Indian mosquitoes do and do not carry human malaria.

(_b_) What are the habits of the dangerous varieties.

I hope, therefore, that I may be permitted to urge the desirability of carrying out this research. It will no longer present any scientific difficulties, as only the methods already successfully adopted will be required. The results obtained will be quite unequivocal and definite.

But the inquiry should be exhaustive. It will not suffice to distinguish merely one or two malaria-bearing species of mosquito in one or two localities; we should learn to know all of them in all parts of the country.

The investigation will be abbreviated if the dangerous species be found to belong only to one class of mosquito, as I think is likely; and the researches which are now being energetically entered upon in Germany, Italy, America, and Africa will assist any which may be undertaken in India, though there is reason for thinking that the malaria-bearing species differ in various countries.

As each species is detected it will be possible to attempt measures at once for its extermination in given localities as an experiment.

I regret that, owing to my work connected with _kala-azar_, I have not been able to advance this branch of knowledge as much during my term of special duty as I had hoped to do; but I think that the solution of the malaria problem which has been obtained during this period will ultimately yield results of practical importance.

FOOD POISONING.

BY VICTOR C. VAUGHAN,

PROFESSOR OF HYGIENE IN THE UNIVERSITY OF MICHIGAN.

Within the past fifteen or twenty years cases of poisoning with foods of various kinds have apparently become quite numerous. This increase in the number of instances of this kind has been both apparent and real. In the first place, it is only within recent years that it has been recognized that foods ordinarily harmless may become most powerful poisons. In the second place, the more extensive use of preserved foods of various kinds has led to an actual increase in the number of outbreaks of food poisoning.

The harmful effects of foods may be due to any of the following causes:

1. Certain poisonous fungi may infect grains. This is the cause of epidemics of poisoning with ergotized bread, which formerly prevailed during certain seasons throughout the greater part of continental Europe, but which are now practically limited to southern Russia and Spain. In this country ergotism is practically unknown, except as a result of the criminal use of the drug ergot. However, a few herds of cattle in Kansas and Nebraska have been quite extensively affected with this disease.