352 THE NEMOCERA. 



Upon the leaves and stems of various plants. This 

 genus also includes two of the most formidable foes 

 of the wheat crops^ — the common Wheat-fly of this 

 country {C. Tritici), and the Hessian-fly (C.c?e5/rz<c/or), 

 which, although not unknown in Europe, is especially 

 celebrated for the ravages which it has committed in 

 the United States of North America. The mode in 

 which these two flies attack the wheat plant is, how- 

 ever, exceedingly dififerent. The first, which is a 

 small pale-orange fly, about a tenth of an inch in 

 length, with clear and almost veinless wings, fringed 

 with hairs round the edges, visits the flowers of the 

 wheat just as they are opening, and deposits its eggs 

 amongst the organs of the flower, by means of a long, 

 extensible ovipositor. The young lars^se hatched from 

 these eggs are supposed to feed upon the pollen, and 

 thus prevent the fertilization of the seed, by which 

 means it is said that as much as five per cent, of 

 the crop is frequently destroyed. The Hessian-fly, 

 on the contrary, lays its eggs in the stem of the 

 wheat, and the larvse live and feed in its interior, 

 thus weakening it to such an extent, tha,t when the 

 ear begins to be formed, the straw is no longer strong 

 enough to bear its weight, but falls to the ground as 

 though beaten down by strong wind and rain. 



Amongst the species of this group there is one 

 which may be met with in abundance in our houses,, 

 especially during the winter months, which not only 

 does not appear at the first glance to be very nearly 

 allied to the Gnats and Tipul(B, but might even 

 mistaken for a member of a very dififerent order| 

 This is the Psychodon phalcenoides (so called from its 

 general resemblance to a moth), a little active twoJ 

 winged insect, less than the twelfth of an inch in] 



