On the Life-History of the Carabid Beetle Nebria Brevicollis (F.)

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Abstract
To supplement our knowledge of the life-history of Nebria brevicollis (Coleoptera, Carabidae) breeding experiments have been carried out. The egg production capacity appears to be much higher than known from literature. Egg production is positively influenced by the size of the beetles and by favourable conditions during larval development. The continuous presence of a male has a highly positive influence on both the number of eggs produced and the viability of the eggs. The sperm seems to remain viable for only 10-12 weeks and as most beetles have died in November the production of viable eggs will be impossible after December. Development of the lar- vae is influenced both by temperature and by quantity and quality of the food. Lower- ing of temperature prolongs development-as is the case when minimizing the amounts of food. In each instar larvae need to increase about twice in weight before they will moult. Presence of first and second instar larvae late in winter therefore indicates an insufficient food supply accessible in the field. A low feeding level during development also results in small beetles, and field data show that in general the size of these beetles is below that of beetles bred under optimal conditions. The size of the beetles, the presence or absence of first and second instar larvae during winter and early spring, the presence or absence of fully developed flight muscles, all give (indirect) information on the feeding level, and more generally on the overall conditions in the field during larval development. In the study area (Drenthe, The Netherlands) these conditions evidently are suboptimal, but in spite of this Nebria brevicollis is a highly successful species there, being both abundant and widespread

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