Bakfi — The Dimorphs of the Species of Chaitophorus. 87 



lows: Antennal Segment [,0.032mm.; II, 0.02 mm.; much thinner than 

 1 ; III, 0.112 nun. ; IV (0.04S mm. + 0.048mm.); length of the lamellae 

 about 0.004 mm. Length from vertex to tip of cauda, 0.528 mm. Color 

 pale green with dark brown eyes. Type in U. S. National Museum. 



Chaitophorus negundinis Thos. 



This species is intermediate in structure between americanus and japon- 

 icus. It can he separated from either of these by the relative lengths of 

 the antennal segments. It lives upon the boxelder and occurs commonly, 

 sometimes quite abundantly and in destructive numbers in different parts 

 of the United States and Canada. The dimorphs appear in large num- 

 bers during late summer. There are about 22 lamellae around the mar- 

 gins of the abdomen and these are slightly pointed as compared to those 

 met with in some of the other species. Average measurements are as 

 follows: Antennal segment I, 0.032 mm. ; II, 0.032 mm.; Ill, 0.08mm.; 

 IV (0.04 + 0.112 mm.). Length from vertex to tip of cauda, 0.576 mm. 



Chaitophorus testudinatus (Thornton). 



This species can be separated by the distinct sculpturing of the dorsum 

 which makes an arrangement of five rows of longitudinal plates. The 

 lamellae are broad and rounded, in this way resembling those of japonicus. 



Average measurements are as follows: Antennal Segment I, 0.032 mm. ; 

 II, 0.032 mm.; Ill, 0.128 mm.; IV (0.064 + 0.08 mm.). Length of 

 lamellae, 0.58 mm. ; length from vertex to tip of cauda, 0.64 mm. De- 

 scribed from specimens taken at Stettin, Prussia, July 26, 1898, by Theo. 

 Pergande. 



Chaitophorus laricae (Haliday). 



The writer knows nothing of this species. It is figured by Signoret 

 (Bull. Soc. Ent. France, Vol. VIII, IV Series XI). The fact that it was 

 described from larch, whereas all of the other forms live upon maple, 

 casts some doubt around the species and would make its rediscovery of 

 much interest. 



