Factors affecting the abundance of the copra beetle, Necrobia rufipes (Deg.) (Col., Cleridae)

Abstract

Some effects of temperature, relative humidity and food supply on the fecundity, length of adult life and rate of development of Necrobia rufipes (Deg.) are outlined.At 30°C. and 64–70 per cent. R.H., females laid few eggs when supplied with palm kernels as food, whereas when given freshly squashed larvae of Carpophilus dimidiatus (F.) as their only food supply they laid large numbers of eggs.When Aspergillus spp. commonly found on copra of high moisture content were cultured, conditioned and supplied as the only food at 30°C. and 81 per cent. R.H., newly emerged larvae died within two days. Complete mortality also occurred on palm kernels at 30°C. and 64–70 per cent. R.H., although a few larvae survived for 60 days.On copra alone, complete development occurred in all conditions attempted, except at 25°C. and 53 per cent. R.H. Development on this food was most rapid at 30°C. and 81 per cent. R.H. (mean period (larva + pupa) 66·5 days). The addition of fishmeal to copra reduced the mean period of development (larva + pupa) at 30°C. and 81 per cent. R.H. to 42·6 days. The shortest mean period of development (larva + pupa) recorded, 37·9 days, was with larvae of C. dimidiatus as food, at 30°C. and 64–70 per cent. R.H. Rapid development was also achieved by adding larvae of N. rufipes to a culture of Oryzaephihis mercator (Fauv.).