ENTOMOLOGY

BIOLOGICAL NOTES ON BLOODSUCKING FLIES 9l9l5and animals. Sambon considered Simulium as the carrier of pellagra,but his theory has not been substantiated. Jobbins-Pomeroy has givenquite a full treatment of the life history of several species of this genus,and Malloch has presented a classification of our American forms. ThelarVa! breed usually in swift-flowing water.The eggs are small, r ather triangular or ovoid objects, and somewhat:.vellowi h in color after a few days. They are laid in masses on grassblades, or leaves, or on stones and other forms of debris at the surfaceof the water or under the surface. The egg stage varies in each speciesaccording to the temperature, but m Jobbins-Pomeroy's studies of fiveFIG. 43. Larva of a buffalo gnat, Simulium.(Jobbins-Pomeroy.)species, the incubation period ranged from 7 to 13 days. A single femalemay lay f~om 500 to 1500 egg according to published claims.The larVa! are invariably aquatic, and are quite characteristicallymarked by the possession of two large appendages on the head in frontof the antennae, which are provided with f an of long hairs. The e fansserve to brush food particles into the mouth of the larva (fig. 43).The meso thorax is provided with a single retractile proleg armed atits apex by a circular row of short hooklets or spines. This pseudopodwith its sucker is used by the larva in attaching itself to objects. A similarbut larger sucker-like disk is situated on the caudal extremity of thelarvre. Respiration takes place through rectal gills located dorsally tothe caudal sucker. These gins are retractile into the rectum, but are