Insect Physiology Laboratory, Section of Entomology, Department of Zoology, Aligarh Muslim University, Aligarh-202 002, U.P. (India).
The effects of sub-lethal concentrations (10, 15, 20, 25 and 30 ppm) of monocrotophos applied topically on 5th-instar nymphs of Dysdercus cingulatus Fabr. was studied in the laboratory at controlled conditions (29 ± 1°C and 70–808 R.H.). The longevity and weight of the treated nymphs increased linearly and showed positive correlation. On the other hand, fecundity and fertility of the adults emerging from the treated nymphs decreased linearly and showed negative correlation with the increasing sub-lethal concentrations. The LD 50 value representing a very small percentage of monocrotophos (30 ppm/nymph) increased 5th-instar nymphal longevity by 43.14%, whereas the longevity of the adult males and females enhanced by 31.48 and 26.50%, respectively as compared to control. Similarly, the weight of the 5th-instar treated nymphs increased by 15.9%, but adult males and females gained 7.9 and 11.8% more weight as compared to control. On the contrary, fecundity and fertility of the females emerging from the surviving nymphs declined by 18.1 and 22.4%, respectively as compared to controls.
