Ecological Studies On Carabid Beetles

At Schiermonnikoog the population structure of Calathus melanocephalus was analysed during four consecutive years (1962–1965), using the structure of the ovaries (in one year also the testes) as a key to the ages of individual adults. The following conclusions were drawn: 1. Part of the population which emerges June–July, and reproduces in August, hibernates. The ovaries of these individuals are spent with conspicuous corpora lutea. 2. Specimens belonging to this hibernating group resume activity in April and continue to the end of July. The females reproduce in July for a second time. 3. The hibernated specimens may be distinguished from newly emerged females by their clear corpora lutea, and lower mean egg-number. The newly emerged females are immature, or have only inconspicuous corpora lutea. 4. It seems that about one third of the adult population at Schiermonnikoog is of the second year category