USEFt'L 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 lirm, 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). 

 lAhcUnUdae {DnKjon-flies) . 



Imafios 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 njjmi)hs 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 — AescJma jiincea, L., 

 A. r/mndis, L., common especially in mountainous countries. 

 Libellula quadrimaculata, L., migrates, and therefore appears 

 sometimes in large swarms. 



L. depressa, L., very common. 



Order YI. — Hemiptera. 

 The tribe Georores {land-biiris) alone includes insects useful 

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

 Head small and tlat,* generally witli 2 ocelli. Antennae large, 



