254 CONNECTICUT GEOL. AND NAT, HIST. SURVEY [BuU. 



hamules of the second segment composed of large curved mesal 

 hooks and lateral lobes in the form of a rather wide ridge on the 

 side of the latter ; surface of abdomen almost or quite free from 

 hairs, terga 2 and 3 with transverse ridges. 



Female. — Lateral margins of the eighth terga projecting ven- 

 trad in a wide thin plate ; sides of thorax and abdomen yellow to 

 greenish ; femora with basal half or a little more, yellow ; tips of 

 wings sometimes to the distal ends of the stigma, brown. 



Measurements : total length, male 60 mm. ; length of abdomen, 

 male 38, female 37-38 mm. ; length of hind wings, male 45-50, 

 female 45-49 mm. ; width of hind wing, male 12, female 13.5 mm. ; 

 length of stigma, male 6, female 6.5-7 mm. 



There are two other recognized varieties, vibrans axillena, and 

 vibrans inccsta (PI. xxi. Fig. 2), the former differing from v. 

 vibrans (PI. xxi, Fig. 8) only in having the front, clypeus, and 

 labrum black instead of light-colored. V. incesta, however, is 

 smaller in size and the entire body is bluish pollinose in older 

 specimens. The wings also lack brown marks at the nodus, but 

 the tips of the wings are sometimes brown and there is sometimes 

 a basal streak. The face is yellowish, somewhat brownish above 

 in incesta. The forms v. vibrans and v. axillena have been con- 

 sidered as separate species by many authors, but there is apparently 

 no difference in the genitalia of the different varieties. 



L. vibrans axillena has a costal streak of dark color between 

 nodus and stigma. The measurements of the variety incesta^^ are 

 given below. 



Total length, male 52 mm. ; length of abdomen, male 30 mm. ; 

 length of hind wings, 39 mm. ; width of hind wings, 1 1 mm. ; 

 length of stigma, 5 mm. 



The nymph of incesta has been described by Byers (Ent. News, 

 38: 113: 1927) and is apparently closely related to auripennis, 

 differing from that species in the characters of the key, and also 

 in the lateral spines of segments 8 and 9, which are more incurvate. 



Connecticut. — E^st Haven, 9 July, 1908 (B. H. W.) var. vibrans; Guil- 

 ford, 13 July, 1920 (P. G.) var. inccsta. 

 New England. — July to September. 



Genus Plathemis Hagen 



Nymphs. — Head with 10 lateral setae on the palpi, and about 8 

 mental setae. Abdomen with rudimentary dorsal hooks on seg- 

 ments 3-5, and small lateral spines on segments 8 and 9; anal 

 appendages not decurved, the laterals about half the length of the 

 inferiors. 



Adults. — Wings with more than 10 antenodal cross-veins; 

 proximal and distal margins of the stigma parallel, more than 3 



^ Libellula vibrans var. incesta Hagen. Synopsis of the Neuroptera of North 

 America, i.i;s, i86i. 



