Effect of larval starvation on survival and cannibalistic behavior, and adult fertility of the Mediterranean flour moth Anagasta kuehniella (Zeller)

In the present research, we studied the effects of larval starvation on survival rate, incidence of cannibalism and survival time in the larval stage of Mediterranean flour moth, Anagasta kuehniella (Zeller) (Lep.; Pyralidae). Effects of starvation and cannibalism of fifth larval instars were also evaluated on adult's fertility and percentage of female larvae in next generation. All experiments were carried out at 27±2 ºC, 70±5% R.H., and L:D 16:8 h. Feeding of larvae on natural food mixture (wheat flour and bran; 3:1) was considered as the control. According to the results, all individuals of the first and second larval instars, and a high percentage of third, fourth (about 87%) and fifth larval instars (about 73%) died because of starvation but it should be noted that cannibalism behavior increased the survival rate of larvae (about 33-73%) compared to the starvation. Negative effects of starvation were most obvious in first and second larval instars. The mean rate of cannibalism increased significantly on eggs by third, fourth and fifth larval instars and also on larvae by fourth and fifth larval instars. The highest fertility of females was observed in female fifth instars that fed on natural food (the control). Fertility of females that produced from fifth instars that had eggs and larvae cannibalism decreased considerably. Feeding state of fifth instars (natural feeding, starvation, and cannibalism) had no significant effect on the percentage of female fifth instars in the next generation. The results showed that in the case of larval starvation due to transient absence of nutrients, larvae of this species can increase their viability by cannibalizing on larvae of earlier instars or wretched larvae and therefore would increase the opportunities or energy required for penetration into the nutrients.