Effects of cold stress on survival and reproduction of Haematobia irritans (Diptera: Muscidae).

Adult horn fly, Haematobia irritans (L.), survival, mating success, and ovarian development were measured following exposure of pupae to 4 degrees C for 2, 3, and 4 wk, and were compared with an untreated control group held at 29 degrees C. Survival varied inversely with duration of low-temperature exposure, and ranged from 92.1% in the control to 7.0% following a 4-wk exposure. Mating success also varied inversely with duration of low-temperature exposure, and ovarian development was delayed, especially in the week 4 group. Reproductive and population parameters were measured in a 2nd cohort of horn flies following exposure of pupae to 1-4 wk at 4 degrees C, and in a control. Adult longevity varied inversely with duration of exposure. Mean longevity was greatest in the week 1 group at 17.6 d, followed by the control at 14.7 d. Week 4 flies lived an average of 2.2 d and produced no eggs. The preoviposition period was longest in the week 3 group at 7.3 d. In cohort 2, control and week 1 flies produced the highest number of eggs, eggs per female, and eggs per day compared with other groups. Eggs were produced over a mean of 6.8 d by week 3 flies compared with 25.4 d by week 1 flies. Reproductive rates varied inversely with low-temperature exposure duration, as did F1 generation egg hatch, larval development, and adult emergence. Survivorship and fecundity schedules are discussed with respect to the effects of low-temperature exposure duration. The effects of low-temperature exposure duration on horn fly reproduction and life-history patterns are discussed with respect to rearing, storage, and ecology.