The life cycle stages of the spinach moth, Hymenia recurvalis (F.) (Lepidoptera: Pyralidae), was studied on the host plant, purple amaranth, Amaranthus blitum L. (Caryophyllales: Amaranthaceae) and adults was fed with 5% honey-solution. The larva of these moths is a major defoliator of amaranths in Nigeria and could cause total yield loss. The first rearing phase involved transfer of 16day old larvae collected from field on webbed leaves into improvised rearing chamber equipped with regulated conditions of R.H (75±5%) and temperature (24-300C) while the second phase was carried out on tagged webbed leaves under natural conditions. The results indicated that the developmental life history of H. recurvalis consists of the egg, six-larval instars, one pre-pupa and a pupa stage before adult. Each of the life stages was isolated, measured and described. Larval instars were separated on the basis of the cast off exuviae. The life cycle from egg to adult lasted an average of 32.7days while the average egg incubation period was 4.3days. There were six larval-instars with total mean duration of 22.1days. There were significant differences in the body morphometrics of the life stages (P<0.05) for body length, abdominal width and head-capsule. The sex-ratio of male to female was 1:1.09. The potential fecundity of the H. recurvalis was 250.42±15.13eggs per female from dissected gravid females whereas the mean actual fecundity from mated females was 224.9±13.59eggs per female. This in-depth knowledge of biology of H. recurvalis will assist in the development of efficient and ecologically-sound management strategies for its control.
Keywords: Hymenia recurvalis; Amaranthus blitum; life cycle; body morphometrics; fecundity; sex ratio.