Effect of temperature and humidity on the biology of Attagenus fasciatus (Thunberg) (Coleoptera: Dermestidae)

The effect of temperature and relative humidity (r.h.) on the biology of the carpet beetle Attagenus fasciatus was studied under laboratory conditions. The influence of two temperatures (30 °C and 35 °C) and three humidities (40, 60 and 80% r.h.) on the number, duration, mortality and pupation of larval instars, as well as on the biology of fed and starved adult beetles, was investigated. Attagenus fasciatus larvae were reared on dried milk. The mean duration of each successive larval instar generally increased slightly but there was much fluctuation, particularly for the later instars. The highest mortality was recorded during the first two or three instars. At 30 °C pupal duration decreased with increasing r.h. while at 35 °C there was a slight increase. However, the duration at 35 °C was always shorter than at 30 °C. There was 100% emergence of adults from pupae under all test conditions except 40 and 60% r.h. at 35 °C where it fell to about 90%. Humidity and starvation strongly affected egg hatchability under all conditions tested. At 35 °C, eggs took less time to hatch than at 30 °C and there was a positive correlation between egg duration and r.h. The duration of the egg stage was longer for eggs of starved females than those of fed ones. Adult longevity was longer at higher humidity, females lived longer than males and unmated beetles lived longer than mated ones. Starvation reduced adult longevity in all cases. The sex ratio was male biased at 30 °C except at 80% r.h. but the reverse was true at 35 °C.

Research highlights
► The mean duration of successive larval instars of Attagenus fasciatus increased slightly.
► Humidity and starvation strongly affected egg hatchability under all conditions tested.
► At 35 °C, eggs took less time to hatch than at 30 °C; the duration was longer for eggs of starved females than those of fed ones.
► Adult longevity was greater at higher humidity, females lived longer than males and unmated beetles lived longer than mated ones.
► The sex ratio was biased towards males at 30 °C except at 80% r.h., but the reverse was true at 35 °C.