CULISETA INCIDENS 481 



hair-tuft at tip; outer half sparsely haired without; two stout separate fila- 

 ments situated near suture subapically. Palpus moderate, with small apical 

 digits. Thorax rounded, wider than long, robust; hairs ajjundant, the single 

 hairs rather long, prothoracic tufts multiple and nearly as long as head. Abdo- 

 men stout, the anterior segments short ; hairs rather short, lateral hairs multiple 

 to fifth segment, double on sixth, single on seventh, confused by subdorsal and 

 subventral tufts which are rather long on third to sixth segments. Tracheal 

 tubes moderate, not band-shaped, flexuous posteriorly. Air-tube stout, tapered 

 outwardly, two and a half times as long as wide ; pecten of small teeth at base 

 becoming long hairs beyond basal fourth and running to apical third ; a large 

 tuft close to base, almost at base of pecten. Lateral comb of eighth segment of 

 many spines in a triangular patch; single spine with a round blunt basal 

 production and two similar ones at base of shaft, apical part long, even and 

 rounded, fringed with long spinules. Anal segment about as long as broad, 

 ringed by the plate ; dorsal tuft a group of three hairs and a brush on each side ; 

 a two-haired lateral tuft; ventral brush well developed, with small tufts pre- 

 ceding nearly to base. Anal gills small, shorter than the segment, tips abruptly 

 pointed. 



The eggs are laid in large boat-shaped masses or " rafts." They float on the 

 water, usually at the margin, where they are drawn by capillary action. The 

 eggs hatch in a few days after being laid, the time depending upon the tempera- 

 ture. The young larvae scatter in the water and begin feeding on the minute 

 particles in suspension. The growth is not very rapid, occupying about a month, 

 but varying vnth the temperature and amount of food present. The pupal state 

 lasts but a few days, when the adults are again on the wing. Several broods 

 succeed each other, so that adults occur throughout the season ; the adult females 

 finally go into hibernation to reappear early in spring. The larvas are inhabitants 

 of permanent water, cold spring holes or holes left by overturned trees being the 

 natural breeding-places. They take readily to artificial receptacles, such as 

 water barrels or small ponds in lawns and artificial fountains, when unsupplied 

 with running water. A small current of water is not detrimental to them, speci- 

 mens occurring in the edges of swiftly running ditches and similar locations. 

 Near Los Angeles, California, Dr. Dyar observed larvae in a wooden box inter- 

 posed in a supply pipe of running water; at San Diego, California, in a little 

 stream caused by a leak in a city water main. The larvae do not inhabit foul 

 water, but prefer that which is clear and cold and preferably well shaded. Water 

 which has collected in cellars with concrete floors is especially favorable to them. 

 The species has become semi-domesticated and is the common larva to be found 

 in water barrels in the region west of the Kocky Mountains. Eailroad trestles 

 and stations are generally supplied with rows of such barrels which are kept 

 filled v\dth water for use in case of fire ; these are generally to be found well 

 stocked vpith incidens larvae. Early in the season no larvae will be found, as the 

 adults are only just from hibernation, but later the larvae become increasingly 

 more abundant. The adults are not troublesome. They will occasionally bite, 

 but approach with caution and are easily frightened. On one occasion one of 

 us sat in the woods near Ashford, Oregon, and was approached by an individual 

 of this species. It alighted, but immediately flew away again, on a motion to 

 capture it being made, and lit on a bush about 10 feet off near the ground. Here 

 it remained for fully ten minutes, when it flew up and again cautiously ap- 

 proached. It was captured only at the third approach, Mdthout having bitten. 

 At Mount Shasta, California, a specimen was observed to bite a horse. We have 

 not observed the adults in houses. They frequent woods and the vicinity of 

 their breeding-places. The mating habits have not come under observation. 

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