Recent Studies on the Longevity and Fecundity of Gasteroclisus rhomboidalis (Coleoptera: Curculionidae) on Amaranthus Species

Both the cultivated and the wild spinach (Amaranthus species) have been found to be host to an
important beetle pest Gasteroclisus rhomboidalis. The longevity of the beetles was studied under a
variety of conditions. It was observed that the life span of the beetles varied widely with the beetles
capable of leaving up to 70 days (about 42 days 0n the average). The beetles generally lived longer
under the ambient condition than inside room condition. Studies on the survivorship of the immature
stages of the beetles revealed that the larva has the highest mortality rate amongst stages with the
egg being the highest surviving stage. Studies on the fecundity of the female adult beetles showed
that about 80% of their life span is utilised in egg-laying. On the average, about 2½ eggs are laid per
day (i.e. about 5 eggs laid within 2 days).