Adult
Wing length 2.62 - 3.77 mm; width about 0.89 mm; VR about 1.05.
AR 2.75 - 3.41; frontal tubercles present about 23 µm; 18 - 38 clypeal setae; palpal proportions 5 : 30 : 32 : 43.
LR ant. 1.42 - 1.67; mid 0.58 - 0.62; hind 0.70 - 0.76.
Abdominal segments with broad basal fasciae which extend all the way to the base of most terga.
Pupa Cephalothorax blackish; abdomen infuscate with marginal markings and swim fin blackish. Total length 6.13 - 8.44 mm (males). 65 - 74 recurved hooks on second tergum. Spurs highly variable with from 1 -6 spines, usually more than two. Swim fin with 57 - 85 flattened setae.
Larva a small to medium thummi or semithummi-type (i.e. lateral projections up to about 0.05 mm long); posterior pair of ventral tubules usually longer. Gular region and frontocylpeus pale. Ventral head length 290 - 370 µm. Mentum with pointed teeth; centre tooth tall and relatively narrow, side teeth well separated; 4th laterals slightly reduced (type II). Pecten epipharyngis with 11 - 17 teeth. Mandible with 3rd inner tooth well developed and darkened (type III).
Cytology: 4 pairs of chromosomes with the maturus arm combination AF, BE, CD, G.
Arm G normally paired except in the area of the virtually terminal nucleolus; two
Balbiani rings whose position varies due to inversion polymorphism. No nucleoli
in the long chromosomes. Inversion
polymorphism in arms B, C, D and G.
whiA1: 1a-e, 2d-3, 12-10, 2c-1f, 9-4, 15-13, 16-19; i.e. as maturus A2
whiB1: Puff with distal dark bands near the end of arm, but further from end than in whitseli.
whiC1: 1-6b, 11c-8, 15-11d, 17a-16, 7-6c, 17b-22 ie. as aberratus, pilicornis, tenuistylus, etc.
whiC2: 1-2b, 11bc, 6b-2c, 11a-8, 15-11d, 17a-16, 7-6c, 17b-22
whiD1: 1-3g, 11-18d, 7-4, 10-8, 18g-24
whiE1: 1-3e, 10b-3f, 10c-13: i.e. as frommeri, halophilus,
etc.
whiF1: 1-2, 15e-12d, 8-3, 9-12c, 15f-23
Found: California - horse trough, Santa Clara Co. (type locality); Berkeley, Alameda Co.; 2 ml n. Lafayette,
Kennsington, 1 ml s. Martinez and Wildcat Creek, El Cerrito, Contra Costa Co.;
Pico Rivera, Los Angeles Co., 12 ml ne. Portal, Mariposa Co.; 6274 Arlington, Experimental
Ponds UCR & 448 N. Orange St., Riverside, Riverside Co.; 5 ml n. Vacaville, Solano Co.
Pools and shallow flowing parts of creeks and rivers. The sample from near Vacaville was in sulphurous water.
Pupa with cephalothorax blackish. Length about 9 mm (female) and 6.1 - 8.4 mm (male). Spur with variable number of spines from 1 - 6, mostly with 2 or more.
Morphology described by Sublette and Sublette (1974), cytology by Wülker and Martin (1974), pattern of arm C1 in Wülker (1991) and of arm D1 in Kiknadze et al. (2004).