A Life-history Study ofAnthrenus flavipesLec. (Col., Dermestidae)

Abstract

Anthrenus flavipesLec. (voraxWaterh.), commonly known as the Furniture Carpet Beetle, is a widely occurring species of wool-destroying insect in India. It feeds on woollen materials, feathers, bristles, furs, horse-hair, horny substances and other materials of a keratinous nature. The adult beetles feed on pollen and nectar of flowers in nature and are harmless; and it is the larva which destroys the above materials. The life-history of the pest has been studied at several controlled levels of temperature and humidity, and also in a room where the humidity was controlled at 70–75 per cent. R.H. and the temperature fluctuated between 25 and 31°C. over the year. The results are compared with those of earlier authors. The sex-differentiating characters have also been investigated in the pupa and adult.Temperature influences the duration of the egg stage and the viability of eggs. The incubation period of eggs at 25, 30, 25 to 31, 35 and 37·5°C. is about 13, 8, 7, 6 and 4 days, respectively. The viability of eggs is greater at 25 to 31, 35 and 37·5°C. than at 25 and 30°C. The fluctuating temperature (25 to 31°C.) has a more favourable effect on the incubation period and viability of eggs than the constant temperatures of 25 and 30°C. Humidity, however, has no effect on either the duration of the egg stage or the viability of eggs.Temperature has a marked effect on the total larval period and to a lesser extent on the number of larval instars. The larval period is appreciably less at 25 to 31°C. and 35°C. than at 30°C. The number of larval instars is greater at 30 and 35°C. than at 25 to 31°C. though the duration of each instar is less at 35°C. than at 25 to 31 and 30°C. The fluctuating temperature (25 to 31°C.) is more favourable to rapid larval development than the constant temperature of 30°C. and also reduces the number of instars. Humidity has no effect on the number of larval instars and the total larval period.Larvae thrive most satisfactorily on woollen fabric treated with 10 to 20 per cent, commercial yeast.The duration of the pupal period and the number of adults emerging are dependent on temperature. The pupal period is about 14, 12, 9 and 7 days at 25, 25 to 31, 30 and 35°C. and is nearly the same for the male and the female. Humidity has no effect on the pupal period. These results are discussed in relation to those of earlier workers.The pre-emergence (quiescent) period extends over 7 to 9, 7 to 8, 6 to 8 and 5 to 6 days at 25, 25 to 31, 30 and 35°C., respectively, irrespective of sex. Humidity has no appreciable effect on this period. These results are at variance with those reported by earlier workers.The length of life of the adults is dependent on temperature but humidity has no appreciable effect on this period. The nature of food influences the length of life of the adults. A female starts laying eggs 4 to 10 days after emergence, depending upon temperature and humidity, and lays 12 to 41 eggs. The sex ratio between male and female was found to be 0·8:1.The entire life-cycle is shortest at 35°C. Under conditions similar to those of the experiments described, there are one to one-and-a-half generations of the insect in a year depending upon the temperature conditions.