author(s)
Muhammad Tanani

abstract
The desert locust Schistocerca gregaria is a dangerous pest devastating agricultural productions and pastures in different countries. The objective of the present study was to assess the dual effect of cycloheximide (RNA and protein synthesis inhibitor), JH-like activity and anti-JH activity, against this pest. Five doses (200, 100, 30, 20 and 10 µg/nymph) were topically applied onto the sternites of newly penultimate (4^th) instar nymphs S. gregaria in Faculty of Science, Al-Azhar University, Cairo, Egypt. Cycloheximide exhibited a toxic effect on nymphs and adults. LD₅₀ was 8.53 µg/nymph. It exerted a potent suppressing action on nymphal growth and developmental rate. As a symptom of the suspended development, some of the treated 4^th instar nymphs failed to moult into the next instar but remained as permanent nymphs and died after 4-fold period of the control nymphs. The successfully moulted 5^th instar nymphs suffered an impairing action of cycloheximide; since malformed nymphs were produced and died after a few days. Some of the treated nymphs precociously metamorphosed into adultoids, skipping off the 5^th instar. These precocious adultoids spent more than one month and eventually died with mating. In addition, cycloheximide induced solitary tendency in the treated 5^th instar nymphs, at the lower two doses.