Studies on Beetles of the Family Ptinidae. VI.—The Biology ofPtinus fur(L.) andP. sexpunctatusPanzer

Abstract

The development ofPtinus fur(L.) andP. sexpunctatusPanzer at 70 per cent. R.H. and several temperatures has been studied.The optimum temperature for rapid development ofP. furis about 23°C., at which temperature it completes its development in a mean period of 132·1 days on fishmeal. ForP. sexpunctatusthe optimum temperature for rapid development is slightly below 30°C., development being completed in approximately 111 days on wheatfeed at this temperature.Eggs ofP. sexpunctatus, but not those ofP. fur, hatch at 30°C., which is near the maximum temperature for development ofP. fur.Larvae ofP. furnormally moult three times at 23°C. on fishmeal, but some have an extra moult.Well defined diapause as mature larvae in cocoons occurs at low temperatures in some individuals ofP. fur; at 23°C. this lasts about 220 days after normal larvae have pupated ; the period at 20°C. is about 280 days. Diapause at this stage also occurs inP. sexpunctatus. In experiments, the development periods of the diapausing and non-diapausing larvae overlapped to form a continuous series.SomeP. sexpunctatuspass through a period of quiescence as mature adults in cocoons ; at 23°C., this lasted 43·5 days on fishmeal and 103·0 days on wheatfeed (mean periods). InP. furthe pre-emergence period is 30 to 60 days, considerably longer than that of other warehouse Ptinids studied.Of the foods, wheatfeed allows the quickest development for both species, but fishmeal produces the heaviest beetles.The adult beetles live for several months. They require food and drinking water. Egg output is small, the mean number of eggs laid per female at 25°C. being 38·6 forP. furand 21·3 forP. sexpunctatus.P. sexpunctatuswas able to overwinter in an unheated outbuilding and could possibly become a pest on some foods.P. furis unlikely to occur in large numbers, owing to its long development period, small egg output and tendency to larval diapause.