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When field-collected larvae of Conoderus exsul and Agrypnus variabilis were maintained in the laboratory on insect (Inopus rubriceps) larvae, plant (germinating wheat seeds), or mixed (both larvae and seeds) diets, mortality was higher and growth rate lower (in A. variabilis) on the insect diet than the other diets. Head capsule measurements indicated at least five larval instars in C. exsul.

Larvae of Inopus rubriceps (Macquart) were reared from eggs originating from spring and autumn adult emergence periods (1975–78), under both insectary and field conditions. Rate of development appeared to depend largely on temperature. Autumn-hatched larvae showed little growth for the initial 6 months, but then grew rapidly until the end of summer. Spring-hatched larvae also grew rapidly over summer, but their development slowed over winter. Year-to-year differences were found in larval survival, weight gain, and rate of development, and in subsequent adult emergence. Pest status appeared to be related to the cumulative yearly heat budget. Overall, larval survival was higher and growth and development were more rapid in the insectary than under field conditions. A male-dominant sex ratio was demonstrated.