Orientational responses of ants (Formicidae) towards the carcasses of the pulse beetle, Callosobruchus chinensis L. (Coleoptera: Bruchidae) in the field conditions

The concept of orientational responses of living organisms was put to experimentation in this study wherein the carcasses of the pulse beetles from the infested pulses in the laboratory cultures were collected and the orientational responses of the ants towards those dead beetles were recorded in the outdoor conditions where there were ant colonies in the vicinity. Two sets of dead beetles: the ones which had died within a week or so (freshly dead-FD), and those which had died more than a month ago (long dead-LD) were used for the field experiments. It was observed that the ants oriented towards the carcasses of beetles, and took lesser time in picking up FD beetles as against the LD ones. It indicates that olfactory stimuli emanating from the former were stronger in eliciting the orientational responses of the ants in comparison to those from the latter. Accordingly, the volatile olfactory cues in the smell from FD beetles could be water-soluble or polar compounds, as the same didn’t emanate from the completely dry dead bodies of LD beetles. In another experiment, turmeric powder was sprinkled on the dead beetles kept in the petri dish containers. It was observed that turmeric powder repelled the ants from picking up the dead beetles or they took much longer time to pick them up than in the ‘control’ condition or in the absence of turmeric powder. It can be inferred from the findings of these experiments that the ants can be employed for easy and effective removal of carcasses of pulse beetles from the infested stored grains in very little time, thereby preventing contamination of pulses from fungal growth which would otherwise occur in the presence of dead beetles. However, the orientational responses of ants towards dead pulse beetles were inhibited by the presence of turmeric powder. Results indicated that the volatile olfactory stimuli play a key role in eliciting the orientation of ants towards dead adults of C. chinensis, and these findings can be exploited in utilizing ants as key biological agents in pest management programs.