The biology of Spodoptera cosmioides (Walk.) was studied on four natural hosts (onion leaves, castor oil plant, soy cv. Embrapa 48 and bean cv. Carioca). The duration and viability of immature phases and total cycle, instar number, pupals weight, sexual ratio, percentage of deformed adults and adults not released of pupal beg, adults' longevity, fecundity and eggs viability were evaluated. It was observed in castor oil plant and onion shorter duration and larger viability of total cycle (39.7 days and 21.7%; 40.5 days and 21.8%, respectively), in contrast of soy (46.0 days and 3.9%). The pupal weight was 444.6 mg on onion, 420.0mg on bean, 396.6mg on castor oil plant and 298.7 mg on soy. Onion and castor oil plant leaves had a predominance of six larval instars, also happening seven for some of them, while in soy the occurrence of seven prevailed, also happening eight instars, indicating less nutritional adaptation of this host. The females had pupal phase significantly smaller than the males in all the hosts, making adults emergency happen before the males. In onion, the longevity of the adults was significantly superior comparing with the other hosts. The fecundity was better on onion and castor oil plant (3224 and 3206 eggs/female, respectively), therefore on soy was observed 1353 eggs/female. In bean leaves, the development of the insect was harmed by morphologic characters, which promoted high mortality in the larval phase.
insecta; bioecology; nutrition of insects
