NOTES ON THE BIOLOGY OF NECROBIA RUFICOLLIS, FABR. [COLEOPTERA, CLERIDAE.

Abstract

SUMMARY. 1 Necrobia ruficollis bred abundantly in the “Fly Room” at the Imperial College of Science, London, in 1917–8. The larvae lived in the debris in the vessels in which houseflies were bred. This debris consisted of remains of food provided for the fly-maggots (a mixture of bread or bran, casein, and banana or beetroot), sawdust, and numbers of empty puparia. 2 During long periods in which the room-temperature was at or above 64°F. (about 18°C.) the Necrobia continued breeding regardless of season. 3 Observations made tend to confirm the view already expressed by some writers, that the larvae of this insect are usually saprophagous, but that they sometimes return to the predaceous habits characteristic of the Cleridae, and kill and devour other larvae. They were observed to eat the soft parts of dead adult flies, and to be attracted to mouldy cheese; they sometimes bore into puparia of flies (two were watched in the act); and with considerable difficulty some were induced to kill and eat fly-maggots. 4 For pupation the larvae make use of existing cavities, and screen over all spaces with hardened, white, opaque, secretion; or they make themselves cells, and line these with the secretion. As recorded by earlier writers, a very frequent method is to enter an empty fly-puparium, and screen over the open end. But they also readily excavated and lined cells in sawdust, sometimes even when empty puparia were ready to their use. Two larvae pupated without any cell or cocoon, but this was probably a result of unfavourable conditions. 5 The adult beetles were observed to eat dead fly-maggots and the soft parts of dead adult flies. They were attracted in numbers to mouldy cheese and to sugar-and water. The evidence was against their killing fly-maggots. 6 Some notes on the form of the larva and pupa are given, including observations which indicate that slight changes in the number of setae, etc., occur at the larval moults.