CHAP. XVI. FAMILIES OF HEMIPTERA. 



113 



species are viviparous, while the last broods of the season are 

 oviparous. 



From their honey-tubes they occasionally eject a sweet fluid, 

 of which the ants and flies are very fond. The Cabbage- Aphis 

 (Fig. 23), the Grain-Aphis (Fig. 291), and the Woolly-Aphis 

 (Fig. 292), belong to this Family. 



MEALY-WINGED BUGS (Aleurodidae). These insects have four 

 opaque wings, which are covered with a mealy powder ; the 

 feet are two-jointed, and the beak apparently arises from the 



