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.
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.
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.