1913. 



NATURAL SCIENCES OF PHILADELPHIA. 



269 



followed in the direction of their flow till each was lost in the woods 

 and it was impossible to trace its course further. 



"The habits of the Agrionines at both locations (Wismar and 

 Rockstone) were identical. They rested on the extreme tips of dead 

 twigs, usually two or three feet from the ground, with outspread 

 wings and rigidly horizontal bodies. The color and the position 

 assumed gave the impression of alertness and self-reliance. The 

 flight was swift, and because of light-conditions also, was difficult 

 to follow. At rest they were fairly conspicuous. When one flew at 

 my approach I stood still and began examining the possible destina- 

 tions in the direction of its flight, and thus located it." 



Variations. — The smallest males are from Potoro Landing, followed 

 in order by those from Tumatumari, Wismar and Rockstone. The 

 order of the females by size from the smallest is not the same, owing 

 perhaps to there being but a single specimen of this sex from 

 Rockstone, viz.: Tumatumari, Rockstone, Wismar, 



The most remarkable variation in this species is in the number 

 of cubito-anal cross-veins, which varies from 1 to 4 on the front wings 

 and from 1 to 5 on the hind. Of the twenty specimens studied only 

 three (all males) have the same number on all four wings, and of 

 these three two have 2 cubito-anal cross-veins and the third three. 

 Two other specimens (females) agree with each other in the number 

 and arrangement of these veins on their four wings, leaving fifteen 

 out of the twenty no two of which are exactly alike in this feature when 

 all four wings are considered. The remarkable nature of this varia- 

 tion will be appreciated when it is recalled that in the great majority 

 of the Agrioninse of de Selys there is but a single cubito-anal cross- 

 vein on each wing. The conditions found in the present material are 

 summarized in the following 



Table II. 



Showing the Number of Wings of Twenty Individuals of Dimeragrion 

 peraihitale having the Specified Numbers of Cubito-anal Cross-veins. 



(The numbers in parentheses are those of the wings in which the most prox- 

 imal of these cross-veins is situated proximad to the level of the first antenodal.) 



