CLASS LNSECTA: OKDER HEMIPTEEA. 



221 



Fig. 378. 



deposited on the plants in the autumn hatch in the 



spring asexual and wingless individuals. These produce 



living young, likewise asexual, in succession, often to 



the twelfth generation. At the close of summer, winged 



and sexual ones appear. These pairing, 



their eggs do not hatch until the following 



spring. This method of propagation is 



called Parthenogenesis. It has been calcu- 



lated that a single Aphis will produce a 



billion joung in a summer. One species 



(Eriosoma lanigera), covered with a woolly, 



flocculent substance, causes the apple-blight by stinging the 



bark, when the leaves turn yellow and drop off. 



Fig. 379. 



Acrydkum aleutactum, Leather-colored Locust (upper figure). 

 Cyrtophyllus concavus. Katydid (lower figure). 



while gorging themselves with the honey extracted from the tender bark, and 

 observe the treatment they receive from the ants, which keep them, as we do cows, 

 extracting from them a sweet liquid of which they are very fond. 



