Disturbance of Epidermal and Fat Body Tissue after Feeding Azadirachtin and its Consequence on Larval Moulting in the Mexican Bean Beetle Epilachna varivestis (Coleoptera: Coccinellidae)
Feeding azadirachtin to larvae (L 3) of the Mexican bean beetle, Epilachna varivestis Mulsant 1850, causes disturbances of the epidermis and of parts of the fat body. Depending upon the point of time of treatment 2 different modes of epidermal degeneration can be observed which both lead to the inability of further moulting. Nevertheless, within some epidermal regions cuticula secretion can be observed suggesting that moulting inhibition may not be necessarily due to hormonal deficiencies. The distal fat body lobes are much more affected by azadirachtin treatment than the proximal lobes are. Firstly, within most of the distal fat cells, the mitochondria change both their size and their shape. This is followed by an increase in autophagy and final disintegration of most of the cells. A special kind of cell death (apoptosis) is described. Effects caused by starvation can be clearly distinguished from those caused by azadirachtin.