glands, and through which saliva is injected when the mosquito bites. Above this, the upper lip, shaped like a grooved director, with the groove turned down, and which, with the tongue, makes a second canal, communicating with the mouth, through which the blood passes into the stomach of the mosquito, during the act of biting. Around these structures, four lancets, two above called the maxillae, two below called the mandibles, and wrapped around everything else, the lower lip, forming a complete tube. There is yet another feature of the anatomy of the adult mosquito to be considered. You remember that in the larval state, the organism consists of a tube within a tube-the body wall constituting the outer tube, and the alimentary canal the inner, and the space between the two tubes being called the perivisceral space, and that in this space the fluid which we loosely call blood circulates, and through this space the subdivisions of the tracheae ramify, reaching every part of the insect. To all intents and purposes this is true of the adult. It is true the stomach is larger, and sexual organs have been developed, but the essential features are little changed. Prior to 1894 there was very little literature on mosquitoes, and very few species had been described. But when it was found that they have a role to play in the transmission of disease, this gave new life to the subject, and scores of investigators all over the world, at once plunged into the study of mosquitoes. And as each one was on untrodden ground he had to adopt his own basis of classification, and create his own terminology, so the only thing that could happen under these circumstances, did happen. The same mosquitoes were described in different parts of the world, by different observers, and on different characteristics, and given different names, so that the most hopeless confusion arose. The yellow fever carrier, for instance, has been christened no fewer than eighteen times, his latest cognomen being Stegomyia calopus, instead of S. fasciata. But out of all this confusion, one fact loomed up very prominently— the fact that there are a good many different kinds of mosquitoes, and the consequent necessity of finding some satisfactory basis of classification. At first, such general characteristics were depended upon, as, color, relative length of palpi, tarsal claws, and venation of the wings. But these superficial characters are too variable to have any great value. At length F. V. Theobald hit upon scale characteristics as a basis of classification, which has gone a long way toward the final solution. He found the scale on the nape, clypeus, and scutellum, belonged to five different types, and upon these he founded the five sub-families: "Megarhina, Resting position of Anopheles above, Culex below. (Howard.) Anophelina, Culicina, Aedomina, and Corethrina." These he subdivided into twenty-four genera, and gradually species after species has been added until now there are no fewer than six hundred and seventy known. Let us now consider a few of the more important species. The Culex pipiens is as we have said, the most generalized, and I may add, one of the most abundant. In this State it is universally distributed. It is this mosquito that is responsible for the transmission of the filaria. The Anopheles are characterized by their resting position, which is quite different from other mosquitoes; by their long palpi, which in both male and female are Anopheles maculipennis, male at left, female at right. (Howard.) about the same length as the proboscis; by their long slender legs; their dark complexion; and by the fact that they are capable of transmitting malaria. Five different species have been reported in this State. Of these the A. crucians is the commonest. It is distinguished from other Anopheles by having three black spots on the last vein of the wing. The A. maculipennis has also been found in Florida but not abundantly. The A. punctipennis was found by the late Dr. Andrade, in Jacksonville, also the A. pseudo-punctipennis, but unfortunately no specimens were preserved. The A. argyritarsis is characterized by having white hind feet. This mosquito is indigenous to Cuba, but has been found only once in this State. That was in Key West. It was possibly brought over in some vessel. Female of Anopheles punctipennis, enlarged. (Howard.) |