478 



NEW YORK STATE MUSEUM 



This is a common species about the upland spring bogs near Ithaca 

 and McLean N. Y. I have collected the nymphs by hundreds from 

 the brownish vegetable debris of the puny streams trickhng through such 

 places. 



The nymph differs from the preceding species in being a trifle smaller, 

 and considerably less hairy; the lateral margins of segments 8 and 9 of 

 abdomen are thin and sharp and bear sharp triangular spines; the labium 

 is less widened just before the bases of the lateral lobes ; the median lobe 

 is less produced, more deeply notched in the middle, and the two lobes 

 separated by this median notch are again cleft by a lesser notch. 



Possibly these differences in median lobe of labium and in lateral 

 margins of abdominal segments 8 and 9 may prove constant for the sub- 

 genera Z o r a e n a and Cordulegaster. 



Skimmers 

 This family is a host, and includes many of the commonest of our 

 species. Most of them are of well sustained flight, and are seen con- 

 tinually hovering over the sur- 

 face of still water, or are met 

 with on the uplands while for- 

 aging. The females do not 

 insert their eggs into the tis- 

 sues of plants, but drop them 

 loosely into the water, or hang 

 them in strings about plant 

 stems at the surface of the 

 water. 



The nymphs are sprawlers 

 on the bottom, mainly in shal- 

 low water, or clamberers over 

 fallen plant stems, and are 

 protectively colored. They 

 agree in the following char- 

 acters : the labium (fig. 17) 

 is masklike, spoon-shaped, 

 with raptorial setae, and with 

 its lateral lobe toothed on its 

 distal margin; the antennae 

 are seven-jointed, and setiform; the tarsi are three-jointed, with the third 

 joint never as long as the two basal ones together; the wing cases are 



- sm — 



t 



Fig. 17 Diagram of the Libellulid nymph labium (P e ri- 

 themis domitia). Sm submentum ; tn mentum; 

 ins mental setae ; ml median lobe ; II lateral lobes ; Is late- 

 ral setae ; t teeth ; h movable hoolc 



