GREEN GRASSHOPPERS (LCCUSTID&). 143 



the ground. The British Meconema varium lays in the 

 galls developed on oaks by the puncture of Cynips. 



FIG. 25. A cave-dweller (Dolichopoda palpatd). 



We find somewhat similar habits in North America, in 

 Xiphidium ensiferum, a very common Locustid in some 

 of the States, the silvery napiform galls produced by 

 a species of Cecidomyia on the stems of willows being 

 selected for the reception of the eggs. The insect 

 thrusts its ensate ovipositor in between the imbricated 

 scales, and leaves the eggs completely concealed, the 

 overlapping edges of the scales springing back to their 

 original positions as soon as the ovipositor is withdrawn. 

 Some of these Cecidomyia galls are more or less fusi- 

 form, with flat, closely applied scales, which are far less 

 well adapted than the more spacious interstices of the 

 globular galls for the eggs. Between the closely 

 appressed scales of the spindle-shaped galls, many are 

 so flattened as to be incapable of developing ; but the 

 Locustids appear to show no preference for the globular 



