INSECTS 



175 



found. By observing a colony of aphids from day to day 

 it may be discovered that the young are born ahve, and 

 are without wings; that feeding is accomplished by a tiny 

 sucking beak, which is thrust into the soft, fresh, plant 

 tissue to suck up the sap; and that each aphid has a 



Fig. 132. — A family of forest tent-caterpillars (Clisiocau'pa disslria), rest- 

 ing (luring the day on the bark, about one-third natural size. (Photo- 

 graph from life by M. V. Slingerland.) 



pair of curious little tubes on its back, which are called 

 honey-tubes. It was long supposed that the honey-dew, 

 a sweetish secretion which the aphids produce, came from 

 these tubes, but it is now known to come from the ali- 

 mentary canal. Several generations of aphids are born 

 alive during the summer, but in the autumn the females 



