ORDER DIPTERA 



271 



large, and those known to be leaf -miners fall within three or 

 four genera, — Pegomyia, Hylemyia, Chirosia, and perhaps 

 Coenosia. 



The two genera first named are well represented in North 

 America and these will be discussed here. 



The eggs. The eggs are linear — oblong, white and rather 

 conspicuous for their size. They are laid singly or in small 

 clusters, flatwise, on the under side of leaves, and on hatching 

 the larvae enter the leaf immediately. The mine is at first 

 linear but very soon it becomes blotched. 



Fig. 88. Larva of Hylemyia fugax. 



The larva. The larvae taper strongly to the front end and 

 are blunt in the rear, with the last segment obliquely trun- 

 cate and tuberculate above. The body segments are trans- 

 versely wrinkled. 



The adult. The flies have a wing expanse of less than half 

 an inch. They are rather slender, grayish in color, and are 

 rather thereby beset with stout black bristles. The legs are 

 blackish in Hylemyia and yellowish in Pegomyia. 



HYLEMYIA 



Many of the species of Hylemyia mine in the roots, stems, 

 and leaves of plants. To this genus belong several well- 

 known species, such as the cabbage maggot (Hylemyia 

 brassicae), the onion maggot (H. antiqua), and the seed-corn 

 maggot [H. cilicrura). There are only a few known North 

 American leaf-mining species in this genus. 



