INSECUTOR INSCITI^ MENSTRUUS 13 



and fitchii. This appears to be a case of change of habits. 

 Concomitantly therewith we find a change in structure, affect- 

 ing, as would be expected, the larva only. The lateral comb- 

 scales are reduced in number and have each a very long stout 

 central thorn, with only small basal lateral fringes. 



The male genitalia scarcely differ perceptibly. The basal 

 lobe and spine are perhaps a little larger than in stimulans, but 

 a trace less than in mercurator, described below. 



No name exists applicable to this form ; but as I have no 

 larval material between Plattsburgh, New York, and Edmon- 

 ton, Alberta, a gradation may exist, and I do not suggest a 

 new name at present. 

 Aedes mercurator, new species. 



Female : Proboscis black ; head with narrow yellow scales, 

 almost replaced by a large black patch on each side. Meso- 

 notum with pale yellow scales, a broad dark brown and black 

 band in the middle ; posterior side-stripes narrow, of the same 

 color. Abdomen black, the basal segmental white bands nar- 

 row, obsolete posteriorly ; a median white spot at base of 

 second segment, forming large triangular patches on the sides ; 

 venter white, with median row^ of black spots. Legs black, 

 with many white scales ; femora white below ; tarsi with white 

 rings at the bases of the joints, broad on the hind legs on first 

 to fourth joints. Wing-scales black. 



Male : Similar. Genitalia : Side pieces three times as long 

 as wide, conical at tip ; clasp with long terminal spine ; apical 

 lobe conical, nearly nude, wath only a few small setae ; basal 

 lobe low-conical, transversely rugose, with non-projecting tu- 

 bercles and short, rather curved setae; a large spine on the 

 basal side. Harpes and unci normal. Harpago with rather 

 short stem, the filament longer than the stem, sickle-shape, a 

 sharp angular expansion beyond the middle. Basal lobes short, 

 with six long terminal spines. 



Types, male and female, No. 23615, U. S. Nat. Mus. ; Daw- 

 son, Yukon Territory, July 16, 1919 (H. G. Dyar). 



Larva : Head hairs, upper 4 or 3, lower 2 or 1, Lateral 

 comb of the eighth segment a large patch of scales, the tips 



