HEMIPTERA 



419 



juices, the Cimicidae or bed bugs, flightless and blood sucking, and 

 the families Nepidae (water scorpions), Hydrometridae or pondskaters, 

 Notonectidae and Corixidae, whose adaptations for aquatic life are of 

 great interest. The Homoptera contain the Cicadidae, large bugs, the 

 larvae of which burrow and suck the root juices of trees (in Cicada 

 septendecim this larval period lasts either thirteen or seventeen years, 

 and the adults appear periodically in vast numbers) ; the Membracidae 

 (tree hoppers) and the Jassidae (leaf hoppers) ; the Coccidae (scale 

 insects),* in which the female is always wingless and usually degenerate 



Fig. 310, External anatomy of Leptocoris trivittatus with wings spread on 

 one side. After Essig. aw. antenna; /?e. hemielytron. 



and covered by a secretion, sometimes waxy and sometimes resinous 

 (forming shellac), and the Aphididae (green flies). In the last family 

 the reproductive phenomena are of immense scientific importance. 

 A comparatively simple life cycle is that of Aphis rumicis. The winter 

 is passed on the spindle tree Euonymus as eggs laid in the autumn 

 after the fertilization of females. In spring these eggs hatch, giving 

 wingless parthenogenetic females which produce young viviparously. 

 A variable number of these parthenogenetic generations is passed 



27-2 



