ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. 5 CENTS PER COPY FIELD IDENTIFICATION OF MALARIA-CARRYING MOSQUITOES. As the transmission of malaria from one individual to another is effected through the exclusive agency of Anopheles mosquitoes, it is desirable that data for the field identification of the commoner of these insects be available to health officers and others concerned. The following schematic outline has been prepared with the idea of affording untrained observers a ready means of identification. For use in the field a small hand lens, magnifying from two to four diameters, is of service, although not essential. Mosquitoes are distinguished from other similar appearing insects by the fringe of scales along the posterior border of their single pair of wings, the wing veins being also fringed with scales. If the insect in hand lacks the posterior fringe of scales it does not belong FIG. 1.-Wing of Culex pungens-Berkeley, 1902, FIG. 2.-Wing of Diptera mistaken for mosquito-F. V. Theobald, Vol. 1, 1901, p. 92, Fig. 23. to the mosquito family, however much it may resemble that insect in appearance. There are three families of insects, the sand flies, the crane flies, and the midge flies, which may be confused with mosquitoes, but ordinarily the health officer will encounter little difficulty in making the differentiation even without examining the wing structure. The sand flies of the United States are much smaller in size than mosquitoes, while the crane flies are not only larger, but the body is long and slender and the length of the legs such as to be out of proportion even to that of the body. Midge flies, often called "midges," are usually seen in dancing clouds hovering over one's head in the late afternoon, and nearly all of those found in this country lack the long proboscis or biting part, have bare wings, and are more delicate than mosquitoes. Some species of Anopheles mosquitoes may fly a mile or more, but such long flights are unusual. Other varieties of mosquitoes are frequently carried several miles by the wind, but visitations of insects in this manner are not followed by outbreaks of malaria, as the insects are never Anophelines. The mosquito can not infect a person with malaria until at least eight days after it has bitten an individual with the malarial parasite in his blood, but once a mosquito is infected she probably remains so throughout life. Mosquitoes may 25511°-18 4 IDENTIFICATION OF MALARIA-CARRYING MOSQUITOES. live five or more months. The life cycle of the Anopheles mosquito includes four stages, the first three of which (egg, larva, and pupa) are invariably passed in water. Determination of sex.-Only the female bites, and for this reason it is essential that the sexes be differentiated. Fortunately this can be easily accomplished. Determination of genus.-After determining that the insect in question is a mosquito and that the specimen is a female, the next step is to decide whether or not it is an Anopheline. In making this decision there are many facts to guide us, each of which must be considered in its turn. For the purpose of comparison the most common variety of mosquito, the Culex, is selected and the differences throughout the various stages of development, beginning with the egg, noted. |