42G 



AN INTRODUCTION TO ENTOMOLOGY 



studded with short and stout excretory tubercles (Fig. 496); from 

 each of these there issues a short, glassy, beautifully iridescent, waxy 

 rod. The second and third instars of this generation are marked by 



a reduction of the antennae, 

 beak, and legs. The fourth 

 instar, which is found about 

 the middle of June, is aley- 

 rodiform (Fig. 497). The 

 fourth and fifth generations 

 resemble the third, there be- 

 ing three aleyrodiform gen- 

 erations. The members of 

 the sixth generation become 

 winged and are the return 

 migrants. These fly to 

 witch-hazel, where they give 

 birth to the seventh genera- 

 tion, which consists of males 

 and oviparous females. 

 These pair and the females 

 lay the winter eggs; each 

 female produces from five 

 to ten eggs. The males and 

 In this species the antenna 



Fig. 496.^ — Hormaphis hamamelidis , first instar 

 of the third generation. (From Pergande.) 



the oviparous females are both wingless. 

 of the winged forms are three-jointed. 



Later experiments by Alorgan and Shull ('10) indicate that this 

 species can complete its life-cycle on 

 the witch-hazel. According to these ,,r"',-T7 



authors there are only three genera- , "^ ''■"",' '"*'''- /, 



tions; first, the stem-mother, which 

 causes the growth of the cone-gall; 

 second, the winged forms, which are 

 developed in the gall and which spread 

 to the leaves ; and third, the males and 

 oviparous females. No aleyrodiform 

 individuals were found on the witch- 

 hazel. 



The spiny witch-hazel-gall aphid, 

 Hamameltstes spinosus.— The winter 

 eggs of this species are commonly de- 

 posited near the flower-buds of witch- 

 hazel, late in June or early in July, 

 but they do not hatch till May or 

 June of the following year. The 

 stem-mother attacks the flower-bud. 



which becomes transformed into a large gall of the form shown in 

 Figure 498. Within this gall the stem-mother produces the second 

 generation; these crowd the gall and develop into winged migrants, 

 which leave the gall, from July to late fall, and fly to birches. The 



Fig. 497. — Hormaphis hamamel- 

 idis, foiirth instar of the third 

 generation. (After Pergande.) 



