Adults of these two species are brown to black with an oblong-oval beetle approximately 1.6 - 3.2 mm long and 0.9 - 1.7 mm wide. Adult khapra beetles are short lived rarely surviving more than 30 days and usually dying within a week of mating. Adult warehouse beetles on the other hand can live for up to 100 days, although average longevity is between 9 to 50 days depending on environmental conditions. Adults of warehouse and khapra beetle can only be distinguished by dissection of the genitalia or by DNA methods.
Larvae of both Khapra and Warehouse Beetles are similar in appearance and can only be separated by expert dissection of the mouthparts. Larvae of both species are approximately 7 mm in length and both have characteristic tufts of body hair. The colour of the larvae changes from yellow-white of the first instars darkening to red-brown of the final instar. Larvae of both species can enter diapause (suspended development) triggered by unfavourable environmental conditions such as low temperatures, crowding and starvation. Larvae entering diapause will usually seek out crevices for protection and can remain in diapause for several years. The survival of larvae through diapause makes eradication very difficult.
Figure 1 Khapra Beetle ( mag.x10), adult (left), larvae (right).
Figure 2 Distribution of warehouse beetle infestations
