. Animal parasites and human disease. Parasites; Medical parasitology; Insects as carriers of disease. LIFE HISTORY OF CHIRONOMIDS 475 rest with the front legs elevated, though not all species have this habit. In most Chironomidae the thorax of the adult insect projects like a hood over the head, but in the subfamily Cera- topogoninae, which alone interests us here, this is not the case, and this negative characteristic is the best distinguishing mark of the subfamily. There are a number of genera and many species included in this group of blood-suckers, but they fall naturally into two groups
. Animal parasites and human disease. Parasites; Medical parasitology; Insects as carriers of disease. LIFE HISTORY OF CHIRONOMIDS 475 rest with the front legs elevated, though not all species have this habit. In most Chironomidae the thorax of the adult insect projects like a hood over the head, but in the subfamily Cera- topogoninae, which alone interests us here, this is not the case, and this negative characteristic is the best distinguishing mark of the subfamily. There are a number of genera and many species included in this group of blood-suckers, but they fall naturally into two groups according to the habits and structure of the larvae. In one, of which the principal genera are Ceratopogon and Forcipomyia, the larvae differ from all other Chironomidae in being terrestrial, living in damp places under bark, stones, moss, etc., and in being covered with spines (Fig. 217). In the other group, of which the principal genus is Culi- coides, the larvae are orthodox in being aquatic and unspined (Fig. 216C); a few spe- FlG- 217' ^?££T2E&*p"","fc cies are marine. Most of the blood-sucking midges become active at dusk, but if dis- turbed they will bite in the shade even on bright sunny days. Life History. — The eggs of aquatic midges (Fig. 216B), sev- eral hundred in number, are laid in water, either floating free or moored to some object. Each one is covered with a gelatinous envelope, and the eggs adhere in chains or in little masses, thus resembling very diminutive bunches of frog or toad eggs. In about six days, more in case of low temperature, the eggs hatch into almost microscopic larvae (Fig. 216C). The latter are worm- like creatures practically without hairs or spines in the aquatic species, but with conspicuous bristles in the terrestrial forms. Usually the only hairs present are in a pair of tufts on the last segment. In most midge larvae there is a footlike outgrowth on the first and last segments of the abdomen. The larvae have inc
Size: 3610px × 692px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyo, bookyear1922
