226 ^flE CANADIAN ENTOMOLOGIST 



at the apices than in coerulea, though the curving is quite noticeable in the 

 figure of coerulea. The lateral spines ou segments 8 and 9 of the abdomen 

 appear to be a trifle shorter in sitchensis. 



The nymphs of these two related species are readily distinguished from 

 all other known nymphs of North American species of Aeshna by the entire 

 lack of lateral spines on the 6th abdominal segment. The nymph of sitchensis, 

 like the adult, is on the whole the smallest of North American species, though 

 coerulea scptcntrionalis is often no larger. A. calif ornica is the only other 

 species that is comparable to these two in its small size. 



Explanation of Plate. 

 Aeshna sitchensis Hagen. 



Fig. 1. Exuvia of full-grown male nymph. The head is slightly bent 

 forward. 



Fig. 2. Head of same, direct dorsal view. 



Fig. 3. Labium (closed), ventral view. 



Fig. 4. Left supra-coxal process. 



Fig. 5. Caudal appendages of male, dorsal view. 



Fig. 6. Terminal abdominal segments of female nymph, ventral view. 



A REVISION OF THE NEARCTIC SPECIES OF THE TACHINID 

 GENUS ERNESTIA R. D. (DIPTERA). 



BY JOHN D. TOT HILL, 

 In charge of Natural Control Investigations, Entomological Branch, Ottawa. 



(Continued from Page 205.) 



Description of Species. 

 Ernestia (Meriania) flavicornis Brauer. 



Head at vibrissae about as thick as at base of antennae; vibrissae well 

 above the oral margin. Palpi yellow. Eyes hairy, checks (below the eyes) 

 white pollinose on a black ground, subshining on the lower hairy part, a row 

 of stouter hairs or bristles at the oral margin. Distance from the oral margin 

 to base of eye equal to about one-third the eye height ; sides of face covered 

 with silvery pollen ; with some weak hairs on the upper part ; narrowest width 

 equal to or slightly greater than the length of the second antennal segment. 

 Facial ridges bristly on the lowest fourth. Facial depression silvery pollinose, 

 without any carina. Antennae reaching the lowest fourth of the face, all three 

 segments rufous; third segment about one and one-fourth times as long as the 

 second. Arista thickened on basal two-fifths to three-fifths, the penultimate 

 segment slightly longer than broad. Width of front in male equal to the 

 length of, in the female equal to two and a half times the length of, the 

 second antennal segment; the front silvery pollinose; frontal vitta dull, dark- 

 brown, at narrowest point equal in male and twice in female the width of either 

 side of front just cephalad of the ocellar triangle. Orbital bristles present in 

 female, absent in male. Ocellar bristles absent in male, present and proclinate 

 in female ; the single row of frontal bristles descending nearly to the base of 

 the third antennal segment. 



