THE CABBAGE-FLY AND ITS ENEMIES. 187 



with fine bristles along the outer or costal edge, nearly to the tip. At 

 the apex of the first vein is a slight notch, where is a coarser bristle. 



" The female differs in having the eyes smaller and farther apart, 

 and the black stripe between them is much broader, and is tinged with 

 tawny-red in its middle, and forked at its upper end, with a small 

 black spot between the forks. The black stripes on the fore body are 

 obsolete, as are also the black bands on the sutures of the hind body." 



Natural Enemies. 



According to Curtis, the cabbage-fly is not known to have any para- 

 site destroying it in Europe. A small four-winged Ichneumon, be- 

 longing to the Hymenoptera, known as Alysia manducator, lives in the 

 pupas of several flies allied to AnfhomyiidcB. It undergoes its transfor- 

 mation in a thin, yellow case, within the pupae, and emerges in the 

 spring and summer, when it' may frequently be seen about decaying 

 turnip and other roots. It may, therefore, be inferred that it is a 

 gerieral parasite of these flies, and that the cabbage and turnip larvae 

 do not escape its vigilance. 



In our own country, a parasite upon A.hrassicce has been discovered, 

 from which much service is expected in checking the depredations of 

 this injurious species. It is a small beetle, belonging to the family of 

 Staphylinidm, vyhich are sometimes known as rove- beetles. 



Tlie Staphylinidm. — These beetles are characterized by their nar- 

 row, elongated and somewhat flattened bodies, which vary iu size 

 from about an inch in length to a microscopic form. Their wing- 

 covers are very short, often extending only over a small portion of the 

 abdomen, leaving the greater part uncovered and left free to be raised 

 upward in running, or employed for folding and packing up the true 

 wings under their abbreviated covers after flight. The end of the body 

 often bears two bristly processes. The jaws (mandibles) are long 

 and curved, and are used in a menacing and formidable manner when 

 the insect is taken in the hand ; when at rest, or in cabinet specimens, 

 they are usually crossed at the tips. The antennae are short, composed 

 of short rounded or lenticular joints, which frequently increase in size 

 toward the tips. Their food consists largely of decaying animal and 

 vegetable matter, rendering them very useful as scavengers. Some of 

 the species attack and destroy other living insects, and are so canni- 

 balistic as to prey upon their own species. Others are true parasites, 

 and find their food in the larvae of ants' nests, in the nests of wasps, 

 in beetles, and doubtless, from recent observations, and an increased 

 knowledge of their habits — in many more insects than are now sus- 

 pected. • The family is a very large one, more than five hundred North 

 American species having been described. Leistotrophus cingulatus 



