USEFUL HEMIPTERA. 197 



The larvae feed greedily on plant-lice, which they suck dry ; 

 they can generally be found wherever the latter are numerous. 



They grow rapidly, and pupate in firm, almost spherical 

 cocoons, suspended by a few threads between leaves, from 

 which the imagos emerge in 2 to 3 weeks. Generation double. 



The commonest species is Chrysopa perla, L. 



ORDER V. ORTHOPTERA (PSEUDONEUROPTERA). 

 Libclhdidae (Dragon-flies) . 



Imagos long, usually very slender and brightly coloured. 

 Head large, almost entirely covered with the large many- 

 celled eyes ; 3 ocelli. Mouth-parts strongly developed. An- 

 tennae short, fine, bristle-like, and generally 7-jointed. Wings 

 of equal size, many-celled, and membranous. Legs short, 

 strong; the tarsi 3-jointed. Abdomen formed of 11 segments, 

 with a short pair of forceps on the last. 



The 6-legged larvae, and nymphs are characterised by an 

 extraordinarily large labium, which can be extended forwards 

 from beneath the head and serves for seizing prey. 



The perfect insects fly in an extremely active manner in June 

 and July, laying their eggs either on the surface of the water 

 or on water-plants. The generation is annual, and dragon- 

 flies appear sometimes in incredible numbers. 



The larvae and pupae live in the water, and prefer small, 

 quiet ponds full of reeds. 



In all three stages, especially as imagos, they kill other 

 insects even moths. 



Species. Blue and green dragon-fly Aeschna juncea, L., 

 A. grandis, L., common especially in mountainous countries. 

 Libellula qiiadrimaculata, L., migrates, and therefore appears 

 sometimes in large swarms. 



L. depressa, L., very common. 



ORDER VI. HEMIPTERA. 



The tribe Geocores (land-bugs) alone includes insects useful 

 to the forester, and they may be characterised as follows : 

 Head small and flat, generally with 2 ocelli. Antennae large, 



