Vol. 31, pp. 85-88 June 29, 1918 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



THE DIMORPHS OF SPECIES OF CHAITOPHORUS. 



BY A. C. BAKER. 



The species of Chaitophorus feeding on maples produce in 

 most species dimorphic forms in summer. These are small pale 

 green flattened forms armed about the margin with hairs or 

 leaf like structures. All the species which the writer has studied 

 with the exception of C. lyropecta Kess. produce these forms. 

 These species are as follows: C. aceris Linn., C. americanus 

 Baker, C. japonicus Baker, C. negundinis Thos., and C. testudi- 

 natus Thornton. There has existed some little confusion in 

 regard to the different species possessing these forms. Ameri- 

 can species have been determined as European ones and the 

 European workers themselves have not been agreed in regard 

 to the different forms. As far as the writer's observations ex- 

 tend, neither of the European forms, aceris and testudinatus 

 occur in this country, but the species distinguished as unde- 

 scribed have often been referred to by these names. While the 

 other forms of the species are often quite difficult to distinguish 

 the dimorphs give a ready means of separating the species with 

 ease, as the following key will show. This key does not include 

 laricae Haliday, which is unknown to the writer. 



Key to Dimorphs. 



1. Armed with long stout hairs aceris Linn. 



Armed with lamellae 2 



2. Antennae nearly as long as the body; haseof distal segment about 



one-quarter as long as unguis americanus Baker 



Antennae considerably shorter than body; base of distal segment 

 one-third to as long as unguis 3 



3. Base of distal segment one-third to one-half as long as unguis 



negundinis Thos. 



25— Proc. Biol, Soc. Wash., 1 ,Vou 31, 1918. (85) 



