THE LIFE CYCLE OF HORMAPHIS HAMAMELIDIS. 



By T II MoKi-.AN and A. F. Shull. 



Pergande* has described the life cycle of this species as con- 

 sisting of seven generations, the tirst two and the sexual genera- 

 tions living on the witch hazel, and the other four on the black 

 birch (Betula nigra), the latter four generations consisting of three 

 aleurodiforms and one winged migrant. 



Failure on our part to discover the aleurodifonn generations 

 in localities where the witch hazel was abundant, and the disco\-- 

 ery that the winged migrants continued to emerge from the galls 

 from the end of July until October, thus leaving no time for the 

 intercalation of the four birch generations, led us to examine the 

 life cycle of this species in the vicinity of New York. 



Leaves of the witch hazel bearing galls of Hormaphis were 

 enclosed in bags of paraffin paper about the first of August, when 

 the migrants had begun to leave the gall. The bags were opened 

 at intervals of about a week, and the under surface of the leaves 

 examined. Nothing was found until about the first week in Sep- 

 tember, when the sexual forms were discovered on the leaves 

 which had been in the liags. At the same time the sexual fornis 

 were also found on the lea\-es outside. The results show at least 

 that the birch is not a necessary link in the life cycle of this species; 

 and since no aleurodiform individuals were seen at any time on 

 the witch hazel, their necessary occurrence in the life history 

 seems, in this locality at least, to be excluded. 



The final and conclusive evidence was obtained from a micro- 

 scopic examination of the migrants within the witch hazel galls, 

 and of the young stages. ])U])al and ])n-'i)U])al. Serial sections 

 show that all these forms contain eml)ryos that are males or fe- 

 males. The determination of the male embryos can be made 

 owing to the fact that the testes early develo]), and in the embryos 

 in the winged stages of the migrant the- characteristic sj^ermat- 

 coyte divisions can be found. In all of these, as in other ajjhids, 

 a lagging chromosome. is present, and two classes of sperm, tune- 

 tional and rudimentary, result. The determination of the sexual 

 female can be made owing to the presence of a sypegesis stage 

 in the eggs in \hv ovary. 



* Pergande, Then. "The Life History of Two Species of Plant-licc Inhab- 

 itinjj Both the Witch-Hazel and Birch." U. S. Dcjit. of At,M-.. Div. of Kntomol- 

 oKV, Technical vSeries No. «), UHll. 



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