THE CANADIAN ENTOMOLOGIKT 225 



proximal fourth of 10. Inferior appendages scarcely longer than segs. 9 and 10 

 together, their apices distinctly incurved; median superior appendage about 

 one-fourth shorter, the basal tubercle in the male triangular, with a blunt, 

 rounded apex, about three-fourths as long as the paired superior appendages 

 (lateral appendages), which in the male are rather more, in the female barely 

 less, thau half as long as the inferior appendages. Ovipositor extending over 

 about one-fourth to one-third of seg. 10, the lateral gonapophyses (genital 

 valves) a little shorter, just about reaching to the base of that segment. 



Colour Pattern. Head almost uniform brownish, thorax with traces of 

 paler mottlings m some specimens. Legs nearly uniform, with more or less 

 distinct traces of two or three pale femoral bands, a median, an anteapical and 

 sometimes a basal band. Abdomen brownish with pale markings almost exactly 

 as in crciuita and iiifcrntpta. Extending practically the entire length is an ill- 

 defined brown median band, which tends to deepen in front of the dorsal punctae, 

 typically forming paired submedian. /\ -shaped spots at the front margins of 

 most of the segments. This band is bordered laterally by a pair of pale bands, 

 which are most distinct on the anterior segments, and on the anterior part of 

 each segment, forming in dark specimens a subcontinuous series of pale spots. 

 Laterad of these bands is a series of subcrescentic pale spots and a broad 

 marginal pale area, just enclosing the lateral scars, which are outlined in brown. 

 Punctae all dark brown. 



Length of body 31.5 to 32.5 mm.; mentum of labium 4.5 to 5.0 mm.; 

 hind wing-pads 7.5 mm.; hind femora 5.5 mm.; inf. apps. 3.0 to 3.25 mm. ; 

 ovipositor 2.25 to 2.5 mm. ; width of head 7 mm. ; width of abdomen 6 mm. 



The immature exuviae are similar to the full-grown examples, except 

 in size and length of wing-pads and genitalia. The paired superior appendages 

 of the males are only about three-eighths the length of the inferior pair, and 

 the ovipositor does not quite reach to the posterior margin of seg. 9 . The colour 

 pattern is similar but darker, and with more distinct markings than in most of 

 the full-grown exuviae. All are of about the same size and the measurements 

 are as follows : — 



Length of body 29 mm.; mentum of labium 3.S mm.; hind wing-pad 

 3.5 mm. ; hind femora 4.5 mm. ; inferior appendages 2.75 mm. ; ovipositor 

 6.0 mm.; width of head 6.0 mm.; width of abdomen 5.5 mm. 



As these exuviae evidently belong to the penultimate stage and as the 

 period of emergence was long -over when they were taken, it is evident that 

 the nymph of Acshna sitchcnsis enters the last stage during the season before 

 that in which it emerges. This appears to be the usual habit in boreal Odonata. 



As compared with Ris's description and excellent photographs (if the 

 female exuvia of A. cocrulea, that of sitchcnsis is seen to dififer very little 

 except in the form of the labium and the somewhat shorter caudal appendages. 

 The body of sitchcnsis is somewhat more slender, a^ is also true of the adults, 

 and the head is a little wider than the thorax, whereas in cocrulea it appears 

 to be of about the same width. The mentum of the labium is distinctly broader 

 in sitchctisis, its greatest breadth being equal to fully four-fifths of its length, 

 while in cocrulea it is equal to about two-thirds of its length. The inferior 

 paired appendages, besides being shorter, appear to be more strongly incurved 



