No. 39] ODONATA OF CONNECTICUT: GOMPHIDAE 141 



Measurements : total length, male 35-36, female 40 mm. ; length 

 of abdomen, male 26-28. female 28 mm.; length of hind wings, 

 male 22-26, female 25-26 mm. ; width of hind wings, male 7, 

 female 8 mm. 



Described from one female and two males in the collection of 

 P. P. Calvert, Philadelphia Academy of Sciences. 



Connecticut. — Cornwall, 16 Tulv, 1013, 28 June, 1918, 8 Tune. I02'? 

 (L. B. W.). 



New England. — May 26-July i. 



Genus Gomphus Leach 



Nymphs, — Proximal segment of labial palpus not truncate; 

 third antennal segment cylindrical ; middle coxae not more approx- 

 imate than the front; no dorsal projections on abdomen; ninth 

 segment without an acute spine at apex. 



Adults. — Subcostal vein absent ; triangles without cross-veins ; 

 anal loop indistinct or consisting of a single cell ; vertex with or 

 without an acute ridge between compound eyes ; dorsum of thorax 

 brown, with green or yellow stripes or yellow with brown stripes ; 

 hind femora with short spines of nearly equal length ; hind femora 

 extending beyond the caudal margin of the first abdominal seg- 

 ment; inferior anal appendages of the male bifurcate, the arms 

 usually widely divaricate. 



Another genus with the rapid dispersal habit. Cast exuviae 

 have been frequently seen in large numbers along the borders of 

 streams or small lakes, but no amount of collecting would appar- 

 ently reveal the adult. The nymphs most commonly inhabit small 

 streams with muddy bottoms into which they burrow and attach 

 to their bodies all manner of rubbish for the purpose of conceal- 

 ment. They are with a few exceptions found on the wing early 

 in summer — May, June or early July — and are most commonly 

 encountered near the streams where the nymphs are found. The 

 eggs of most species are probably laid by the dipping process while 

 the insect is in flight. 



Various authors have attempted to divide Gomphus into a num- 

 ber of groups, but thus far the subdivisions are apparently not dis- 

 tinct enough to warrant splitting the genus. The following 

 groups are offered as an aid to making determinations, but it is 

 realized that they do not agree fully with those of previous authors. 

 They apply only to species found in the northeastern United States. 



1. Brevis and abbreviatus fall into one group, distinguished by small 



size and color pattern, and structure of the nymph (p. 149). 



2. A miscellaneous and not entirely homogeneous group comprising 



exilis, descriptus, spiccitus, and Itvidus, distinguished by the fairly 

 slender abdomen of the adults, not at all expanded. Nymphs of 

 typical form shown in PI. in. Fig. 7 (p. 151). 



3. The pale thorax types including villosipes, furcifer, pallidus, and 



possibly borealis, though the latter may belong in 2. The nymphs 

 of this group have comparatively long teeth on the labial palpi 

 (p. 157). 



