48 THE CANADIAN ENTOMOLOGIST 



THE LARVA AND BREEDING PLACE OF AEDES ALDRICHI DYAR 



AND KNAB. (CULICID^, DIPTERA). 



BY ERIC HEARLE, 

 Dominion Entomological Laboratory, Mission City, B. C. 



Aedes aldrichi is the dominant mosquito in the Lower Eraser Valley, B. C, 

 and the main cause of the serious mosquito pest that at times occurs in that 

 district and casts an evil shadow over the most beautiful period of the year. 

 Previous to the summer of 1920, the larva had been unknown and there were no 

 definite data as to its breeding place. Extensive larval collections have shown 

 the main breeding places to be in the wooded river bottoms. These areas are 

 thickly covered with cottonwood and a tangled low growth of willow, rose and 

 spiraea. They are locally known as alder-bottoms. At freshet time flooding 

 converts them into temporary swamps capable of producing enormous numbers 

 of mosquitoes. Aedes vexans and Aedes cinereus occur with Aedes aldrichi in 

 these alder-bottom areas, but the latter is the chief species. 



Description of Larva of Aedes aldrichi. 



Stage IV. — A stout dark grey larva, very much like that of Aedes hirsuteron 

 and Aedes aestivalis, from which it differs mainly in the dorsal head hairs and, 

 in the case of hirsuteron, in the laterals of the sixth abdominal segment.* 



Head with a dark patch on the vertex; broad, narrowed before the eyes; 

 front roundly arcuate. Antennae, inserted at notch in head, yellowish, moderate, 

 curved, swollen at base, fairly thickly covered with large and small spines; 

 antennal tuft of about seven hairs of moderate length placed a little before 

 centre; at the apex are four short spines, one long spine and one short bud-like 

 process. Eyes transverse and pointed. Upper pair of dorsal head hairs usually 

 in twos and lower head hairs single; ante-antennal tuft of about seven hairs. 

 Mental plate broadly triangular with a small, central tooth and fourteen to 

 seventeen teeth on each side, those toward base largest. Thorax rounded, wider 

 than long, hairs abundant and fairly long. Abdomen stout, anterior segments 

 shorter and broader, hairs sparse, laterals moderately long, secondaries short; 

 laterals usually double from second to sixth segment, but often in threes on third 

 segment; first segment with two pairs of fairly long hairs. Air tube stout, 

 about three times as long as wide; pecten of about seventeen evenly spaced 

 teeth reaching to middle; teeth gradually larger distally; individual tooth a 

 long spine with broad base, a stout spine at base and a very small tooth be- 

 tween this and the main spine; a tuft of six hairs following the pecten. Lateral 

 comb of eighth segment of about twenty-five scales in a broad triangular patch ; 

 scales three deep; individual scales broadly elliptical, fringed with short delicate 

 spines from centre outwardly, a longish stout spine at apex. Dorsal plate 

 reaching nearly to ventral line. Dorsal tuft a brush of about eight hairs and 

 one long hair on each side. Ventral brush well developed. Anal gills ensiform 

 and about twice as long as eighth segment. Skin of larv^a covered with minute 

 spicules. 



*Note. — ^A great deal of variation occurs and a good series is needed to ensure accurate 

 determinations. The dorsal head hairs are net very constant. In many cases the upper dorsal 

 head hairs are in threes and the lower head hairs in twcs, sometimes they occur iVi fours and 

 in threes, but in only a very few specimens examined were the upper head hairs found to be 

 single as in aestivalis. In many specimens some of the abdominal laterals were found to be in 

 threes, but the sixth laterals are always paired, unlike those of hirsuteron, in which they are 



single. 



Mailed February 28th, 1921 



