Effects of Temperature and Humidity on Larval and Pupal Stages of the Common Cattle Grub

Abstract

A study of the effects of temp. and relative humidity on the development of free larvae and pupae of Hypoderma lineatum was made under both field and controlled laboratory conditions. A high survival rate of pupae was found to obtain under field conditions, even when larvae were placed in the field up to 18 days before the normal dropping period. Low temp. tests showed that some larvae survive a temp. of [long dash]20[degree]C but none survive [long dash]25[degree]. A group of larvae was seeded with water and a high percentage of these were frozen and killed when subjected to [long dash]5[degree]C. Pupae were reared at constant temps. of 15[degree], 20[degree], 25[degree], and 30[degree]C. The survival rate of pupae reared at 15[degree] was 44%; at 20[degree], 81%; at 25[degree], 33%; and at 30[degree], 0%. The length of the pupal period was 43.8 days at 15[degree], 19.8 days at 20[degree], and 12 days at 25[degree]C. Two groups of pupae were reared at constant rel. humidities of 0, 32, 56, 76 and 100%, one group at 20[degree]C and one at 25[degree]. Very little difference was found in the length of the pupal period and in the survival rate of pupae reared at rel. humidities ranging from 0 to 76%. At 100% R.H. the pupal period was slightly lengthened and mortality of the pupae was greatly increased. Evidently little aid in control of grubs can be expected in Wyoming from inclement weather during the dropping period.