118 MISCELLANEOUS STUDIES 



and less numerous. No sign of parasites was present, and the pre- 

 daceous enemies were not more abundant than usual, so a search for 

 the cause was made. Within fifty feet of the milkweed plants several 

 oleanders were found and on them was noticed a large yellow species 

 of Aphis. This supposedly was Aphis nerii Fonsc. In the laboratory 

 the author could find no structural difference whatsoever between this 

 species and the one on Asclepias, so he continued to watch them care- 

 fully on the hosts. As the days passed the Asclepias became freer and 

 freer of the infestation, while the Nerium became more and more 

 heavily infested. This continued through September and into October, 

 by which time the Asclepias had died down and incidentally no aphids 

 were left. The Nerium was very heavily infested then. This was 

 taken as a good proof that these were the same species. Later Essig 

 told the author that the summer before (1914) he had made transfer 

 tests in the laboratory of specimens from Asclepias to Nerium and 

 that they thrived there and bred well. This fact and the observations 

 above mentioned were noted in a letter to Davis. Following is his 

 answer : 



I have your letter relative to Aphis asclepiadis and nerii, and am interested 

 in your observations. In 1'914, Theobald described a species under the name of 

 Aphis nigrepes, which he now places as a variety of asclepiadis. He considers 

 nerii as distinct from asclepiadis because the latter lacks the black patches at 

 the base of the cornicles. Passerini's asclepiadis is entirely different from Fitch's 

 Aphis asclepiadis. Fitch's name has priority for, as you will notice, it was 

 described in 1851. This being the case, Passerini's name will have to fall and 

 be replaced by Aphis lutescens of Monell, which according to Mr. Monell 's data 

 does not bear the black patches around the base of the cornicles. 



This would seem to indicate that the California species on Asclepias 

 is Aphis nerii Fonsc. and not A. lutescens Monell, as brought out by 

 Essig 's experiment and by the author's observation. Consequently 

 this Californian species is Aphis nerii Fonsc., with Asclepias for its 

 summer host and Nerium for the winter host. 



136. Aphis oenotherae Oestlund 



Oestlund, Minn. Geol. Nat. Hist. Surv., Bull. 4, p. 62, 1887 (orig. desc.;. 

 Clarke, Can. Ent., vol. 35, p. 252, 1903 (list). 



Record. Oenoihera bectiana; Epilobium sp., Berkeley (Clarke). 



In 1903 Clarke recorded finding this species on primrose and 

 willow herb in Berkeley. Since then it has not been observed in Cali- 

 fornia. The author has had the opportunity to study specimens from 

 Minnesota, taken by A. C. Maxson. 



