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 species' 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 during winter. The sex ratio of wild-trapped N. nigrita was female-biased while laboratory-raised broods were slightly male-biased. Adult male 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 individuals was calculated for Big Creek Canyon. Analysis of mouse carcass transect data indicated that N. nigrita adults located dead mice more successfully in moist, cool, redwood-forested canyons than in six other habitat-types. Vertebrate scavengers, flies and ants were the most common competitors of N. nigrita for mouse carcasses. The reproductive biology of this species differed only slightly from known Nicrophorus biology. Carcass mass strongly predicted the mean pronotal width of the offspring in a brood. Nicrophorus nigrita differs from Nearctic congeners in the lack of elytral maculations, the greater length of time required to complete development from larva to adult and an apparent lack of reproductive diapause. It only shares year-round activity with Nicrophorus mexicanus Matthews.