FLEAS. 55 



where it has spread rapidly. It has also been found in Madagascar 

 and China. The natives in Africa who neglect to remove them 

 frequently lose their toes in consequence. 



Perhaps of all insects flies are man's greatest enemies, injuring 

 his crops, fruit trees and vegetables, whilst others attack domestic 

 animals, or are the means of conveying disease. 



They are very diverse in their habits, even in the same family. 



The Cetidomyiidffi are extremely small delicate flies. The larvae 

 of many species form galls, or swellings in the stems of plants. 

 Oligotrophus anmdipes (Hormomyia piligerd) forms hairy tubercles 

 on the upper surface of beech leaves (see model no. 87 on the east 

 side of the gallery). Contarinia tritici, a Corn Midge, is injurious 



Fig. 60. 



Jigger flea (Sarcopsylla penetrans}. Female with the abdomen distended. 

 (Enlarged 10 times.) 



to oats and barley. Mayetiola (Cecidomyia) destructor, the Hessian 

 Fly, often causes serious damage to barley in some parts of the 

 world. In England it appears to be kept in check by the numerous 

 parasites to which it is subject. 



BiMonidm. The larvse of Bibio live on decaying vegetable matter 

 in the earth ; and when they come in contact with the living roots, 

 they eat these. In this way, Bibio hortulanus, sometimes called 

 a Fever Fly, does considerable damage to hops. The flies often 

 appear in great numbers in the spring for a few days, and are seen 

 crawling and tumbling about on the ground. 



Culicidw. Gnats, for which the Spanish word, mosquito, is often 

 used, have of late years come much into notice in consequence of 



