Great Basin Naturalist


Cicindela arenicola Rumpp is being considered for threatened and endangered status by the U.S. Fish and Wildlife Service. Little is known about the developmental biology of this species.

Adults of C. arenicola were active from April through late June and late August through early November, but generally they were not on the surface when temperatures were below 19 C or above 45 C, or when conditions were windy, cloudy, or rainy. Mating and egg-laying occurred only during the spring.

Five size classes (1-, 2-, 3-, 4-, and 5-mm diameters) of larval burrow openings were observed. Burrows of 5 mm had a mean depth of 42.23 ± 8.81 cm (1 S.D.). Larvae of C. arenicola were active from April through June and late September through mid-November.

Developmental times and larval size were affected by food supplementation. Nearly all food-supplemented, 1-mm, first instars molted to larger second instars of 3-mm diameter. Most nonsupplemented larvae spent several months as 2-mm second instars before growing to 3 mm in diameter. Food-supplemented larvae reached the third instar in approximately 13 months, while nonsupplemented larvae took slightly over two years to reach this stage. Development from egg to adult was estimated at two years for food-supplemented larvae and three and one-half to four years for nonsupplemented larvae.

Cattle had a significant effect on larval mortality. A high percentage (76–80%) of larval C. arenicola that were stepped on by cattle never reopened their burrows. Only 14% of undisturbed larvae never reopened their burrows. Approximately 15% of 150 larvae marked in 1988 reopened burrows in 1989.