244 Maine: agricuIvTural e;xpe;rime;nt station. 1911. ■ 



Pe;MPHIGUS T]iSSE;ivI.ATA (aCERIFOLIi) 



on Alder and Adaple.* 

 Edith M. Patch. 



Since the identity of Pemphigus tessellata Fitch 185 1 and P. 

 acerifolii Riley 1879 was suggested (Patch 1908) the three 

 succeeding years' observations confirm the previous, evidence 

 and leave no room for doubt that the alder and maple repre- 

 sent two hosts of a single species, the alder being the summer 

 home of the progeny of the migrants from the maple. 



But, as the life-cycle outline on page 247 indicates, we do not 

 here have a simple case of alternate hosts ; for the alder, besides 

 serving for summer host for the progeny of the maple migrants, 

 maintains a continuous series of apterous viviparous partheno- 

 genetic females Thus, ignoring the maple for the present, we 

 have on the alder for the first spring generation the hibernat- 

 ing nymphs which over-winter under fallen leaves or loose 

 earth at the base of the alder. These young nymphs climb up 

 the alder stem on the first warm spring days sometimes in late 

 March but usually in April in the vicinity of Orono. This 

 apterous viviparous parthenogenetic generation becomes mature 

 late in June and the progeny, a similar generation, matures 

 about the middle of July. The third generation of viviparous 

 parthenogenetic females becomes mature about the first of Sep- 

 tember. Part of this third generation are apterous and the 

 progeny of these are the hibernating nymphs which become the 

 first generation of the following spring. 



But, as is indicated, part of the generation maturing about 

 the first of September are winged. These, sexuparae or moth- 

 ers of the true sexes, migrate to the maple where they do not 

 settle to feed but seek rough places in the bark in which to de- 

 posit the almost microscopic apterous oviparous females and the 

 still smaller apterous males. The over-wintering eggs are very 

 soon deposited by the minute females, which like the males, die 

 without feeding, both being without functional mouth parts. 

 The stem-mothers hatch from these eggs about May 6 (Aphid 

 2-09). Their full career has not been followed but a mature 

 stem mother (Aphid 9-09) was found on June 11 recently set- 



* Papers from the Maine Agricultural Experiment Station : Entomol- 

 ogy No. 49. 



