The effect of temperature and relative humidity upon the development and fecundity of Dermestes lardarius L. (Coleoptera, Dermestidae)

Abstract

Dermestes lardarius L. larvae were bred on a diet of fishmeal, wheat-germ, yeast and cholesterol at 12.5, 15, 20, 25, 30 or 32.5°C with a constant 65% r.h. and at 25°C with 40, 50, 60, 70 or 80% r.h. Whenever possible emerging adults were paired and kept under the same conditions when their fecundity and longevity were recorded. Complete development of some larvae occurred under all conditions except 12.5°C but 12 of the 13 adults produced at 15°C were deformed and mortality at 32.5°C was very high. The period from egg hatch to emerged adult ranged from about 145 days at 15°C to about 48 days at 25°C and above: little difference was noted in the rate of development of males and females. The weight of adults produced increased with temperature up to 30°C. At 25°C most rapid development was found at the highest humidity used. Adults lived from up to 61 days at 15°C to over 300 days at the higher humidities at 25°C. Above this temperature life was shorter, up to 169 days at 30°C and up to only 23 days at 32.5°C. No eggs were obtained from pairs reared and subsequently kept at 30° and 32.5°C. Eggs were laid at 20° and 25°C and two types of oviposition pattern were noted. There was always a main oviposition period starting about 100 days after emergence and lasting about 90 days, but in some cases there was also a period of oviposition which started a few days after emergence and lasted for up to a month. Temperature and humidity had little effect upon the length of the main pre-oviposition and oviposition periods but the early oviposition period was found at 25°C only and occurred most frequently at 80% r.h. Within the main oviposition period many more eggs were found in the three days following access to a drink of sugar solution than in a similar period when no such drink was offered. The number of eggs laid by a female in the early oviposition period varied from 3 to 38 and in the main oviposition period from 26 to 131. Egg mortality was very variable and the mean percentage hatch was relatively low (about 50%). The comparative value (in terms of rate of increase) of the first egg laid in the early oviposition period at the optimum condition (25°C, 80% r.h.) is calculated to be 25 times that of the first egg in the main oviposition period. Values for the first eggs in other conditions are given.