THE NATURAL-HISTORY OF NICROPHORUS-NIGRITA, A WESTERN NEARCTIC SPECIES (COLEOPTERA, SILPHIDAE)

Nicrophorus nigrita Mannerheim is an atypical Nearctic burying beetle due to its lack of dorsal, elytral maculations. Aspects of this specie s' natural history were investigated and compared to those of Nearctic congeners. Adults from a central Californian coastal population were found to be crepuscular and active year-round, with minimal activity d uring winter. The sex ratio of wild-trapped N. nigrita was female-bias ed while laboratory-raised broods were slightly male-biased. Adult mal e pronotal width was greater than that of females (mean +/- SD) (5.84 +/- 0.74 vs. 5.67 +/- 0.66). A minimum population size of 4565 individ uals was calculated for Big Creek Canyon. Analysis of mouse carcass tr ansect data indicated that N. nigrita adults located dead mice more su ccessfully in moist, cool, redwood-forested canyons than in six other habitat-types. Vertebrate scavengers, flies and ants were the most com mon competitors of N. nigrita for mouse carcasses. The reproductive bi ology of this species differed only slightly from known Nicrophorus bi ology. Carcass mass strongly predicted the mean pronotal width of the offspring in a brood. Nicrophorus nigrita differs from Nearctic congen ers in the lack of elytral maculations, the greater length of time req uired to complete development from larva to adult and an apparent lack of reproductive diapause. It only shares year-round activity with Nic rophorus mexicanus Matthews.