INSECTS. 159 



on the lower side of the leaves of cabbage, rape, and 

 other crucifers. Habits : The pupa lives through the 

 winter ; the moths emerge in May, and fly about in 

 the evening. Two generations; the first generation 

 of caterpillars in the first half of July, the second in 

 late summer. The second generation is particularly 

 apt to be destructive to cabbage. Pupse found on 

 the leaves of the plants attacked, and surrounded by 

 a thick web. 



Sixth Order: Hemiptera (Half-winged Insects). 



The mouth parts are modified into a sucking and 

 piercing beak. Head small. Legs usually slender, 

 with two- or three-jointed feet. Wings are absent in 

 several species (e.g. bed bugs); in one section (e.g. 

 fruit bugs) the fore wings are half of 

 leathery, half of membranous texture 

 (Fig. 107) ; in others, all four wings 

 are membranous (winged plant lice), FiG.iot-Leftpairof 

 or the fore wings are somewhat harder ''"'g^ ot a Bug. 

 than the hind wings (frog-hoppers). Incomplete meta- 

 morphosis (p. 89). None of agricultural importance 

 except — 



Family: Aphidae (Plant Lice), 



Long, five- to seven-j ointed antennae. Long thin legs, 

 no power of springing. Sucking beak long and thin. 

 In the same species there are both winged and wing- 

 less aphides, mostly the latter. In autumn, male and 

 female specimens are found. After pairing, the latter 

 lay their eggs, which are destined to live through the 

 winter. The aphides hatched from these the follow- 

 ing spring are all females, but are distinguished from 

 those of the previous autumn by producing living 

 young, which contain at the time of their birth the 

 germs of a new generation. The number of young 

 produced by a single female, and the number of 



