BRITISH INSECTS 



been noticed by the reader, and wonder expressed as 

 to the cause of them. In a way these are galls, caused 

 by a fungus {Exoascus turgidus), but this does not come 

 within our province to deal with here, and is only men- 

 tioned as a matter of interest in passing. Of the Ichneti- 

 monidce, their parasitism, and usefulness in keeping 

 other forms of insect-life in check, much might be 

 written, but as there are several thousand British species, 

 the task is an impossible one on the present occasion. 

 Perhaps one of the commonest Ichneumons is Ophioti 

 luteus. It does not possess an English name. Some 

 Ichneumons are very small, almost microscopic, others 

 are two inches across the wings. As a rule, they have 

 long thin bodies, and very long legs and antennae. The 

 female Ichneumon Fly has a sharp-pointed ovipositor, 

 and with this she punctures a hole in the larva of some 

 other insect, and deposits an egg. The smaller Ichneu- 

 mons lay several eggs in the body of the larva, the larger 

 species only place one egg in the body. In a few days 

 the Ichneumon larva hatches, and commences to feed 

 upon the body of its host, leaving the vital parts until 

 last. Meanwhile, the doomed host goes on feeding, 

 until the inside tenant is ready to consume the remainder. 

 This it does, and having become full-fed, and its host 

 eaten up, it finds its way out of the larval skin (all that 

 is now left of its host), and at once spins a yellow cocoon 

 on the outside skin, and pupates. The perfect insect 

 eventually emerges, ready to carry on the work of its 

 ancestors, and it is perhaps of interest to note that, in 

 104 



