No. 39] ODONATA OF CONNECTICUT: LIBELLULIDAE 24I 



Adults 



I. Male with prominent ventral hook on first abdominal segment; 

 structure of ventral surface of abdomen of the female as shown 



in Fig. 63, No. 2 Plathemis, p. 254 



Male without a prominent ventral hook on the first abdominal seg- 

 ment ; ventral surface of abdomen of female not as in Fig. 63, 

 No. 2 Libellula, p. 241 



Genus Libellula Linnaeus 



Nymphs. — Head with 5 to 9 lateral setae on the palpi, and 8 

 to 12 on mentum. Dorsal hooks on abdomen present or rudi- 

 mentary, the lateral spines on segments 8 and 9 small ; anal appen- 

 dages not decurved ; laterals about half the length of the inferiors. 



Adults. — Front wrinkled, the vertex projecting over the median 

 ocellus, truncate and usually concave at tip when viewed from 

 above ; wings with more than 10 antenodal cross-veins ; stigma 

 with proximal and distal margins parallel, more than three times 

 as long as wide, and supported by three or more cross-veins ; 

 triangle 3-sided and considerably farther distad in the front wings 

 than in the hind ; vein Mj with a conspicuous bend about as far 

 distad as the proximal end of the stigma; subtriangle absent; 

 Cu^ arising exactly from the caudal angle of the triangle in both 

 wings ; prothorax with caudal margin entire ; meso- and meta- 

 thorax hairy ; femora, tibiae and tarsi with a double row of heavy 

 spines beneath, the femora usually with one dorsal carina and the 

 tibiae with two ; tarsal claws with ventral tooth considerably 

 beyond the middle, the proximal portion of the claws much thicker 

 than the distal ; abdomen without ventral hooks on the first 

 abdominal segment of the male ; transverse median carinae on 

 segments 2 and 3 sometimes wanting on 2 ; general color usually 

 brown or black, often becoming pollinose. 



For literature on adults of the genus, see 

 Byers, C. F. Ent. News. 38: 113-115: 1927. (Key to Libellula nymphs.) 

 Ris, F. Catalogue des Collections Zoologiques du Baron Edm. de Selys 

 Longchamps. Libellulinen ; xi : 245-282: 1910. 



For the most part fresh water species are included in this genus, 

 although the only representatives of auripcnnis were taken near 

 brackish water. The nymphs occur in trash near the borders of 

 ponds or streams. The adults are perhaps our most common 

 dragonflies occurring throughout the summer in many localities. 



Key to Species 



Nymphs'" 



I. Dorsal hooks on the seventh and eighth abdominal segments, long 



and sharp 2 



Dorsal hooks on the seventh and eighth abdominal segments rudi- 

 mentary, hidden among scurfy hairs or wanting 6 



' This key applies only to full-grown individuals. 



