Ds. Sikes, THE NATURAL-HISTORY OF NICROPHORUS-NIGRITA, A WESTERN NEARCTIC SPECIES (COLEOPTERA, SILPHIDAE), The Pan-Pacific entomologist, 72(2), 1996, pp. 70-81
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.