Environmental stress in the pasture Scarab Sericesthis nigrolineata Boisd. II. Effects of soil moisture and temperature on survival of first-instar larvae.
In the work described in this second part [cf. preceding abstract], first-instar larvae of Sericesthis nigrolineata (Boisd.) were exposed, for various periods of up to 8 days, to a range of soil moistures equivalent to pF 1-5.8 at temperatures from 16 to 45 deg C. Maximum survival occurred at pF 2.7-4.2, equivalent to soil moistures of 5-10% in silt and 6-12% in loam. In drier soil, water loss was rapid and most larvae died in one day. Increase in temperature in the range 16-30 deg C caused a greater mortality in dry soil. In soils moister than pF 2.7, there was a significant increase in mortality after 2 and 4 days but the cause of death could not be identified. After all treatments, the larvae were maintained under optimum conditions until after ecdysis. No residual effect of temperature or moisture stress was apparent from a comparison of survival data before and after moulting.