Reproductive diapause in North American populations of the introduced lady beetle hippodamia variegata (Coleoptera: Coccinellidae)

The Palearctic lady beetle species, Hippodamia variegata (Coleoptera: Coccinellidae), first collected in 1984 near Montreal, Quebec, Canada, is expanding its distribution into northeastern and north central portions of North America. Examination of responses to abiotic factors that influence the seasonal biology of H. variegata may provide insights into its potential range expansion in North America. The induction and duration of adult hibernal diapause in three North American populations of H. variegata, collected between 40°N and 44°N latitude, was determined at four constant photoperiods (L:D 16:8, 14:10, 12:12, and 10:14) at 22°C. Thirteen to twenty-one percent of females reared at L:D 16:8 entered diapause, whereas shorter photoperiods (L:D 12:12 and 10:14) induced diapause in 100% of females. Variation in the response to L:D 14:10 was observed among the three populations, 27-100% of females exhibited reproductive diapause. Pupae and young adults were sensitive to changes in constant photoperiods (L:D 16:8 ‡† 10:14). Individuals reared at L:D 10:14 that were moved to L:D 16:8 on the day of pupation or the day of adult eclosion produced ovipositing females. Individuals reared at L:D 16:8 and transferred to L:D 10:14 on the day of pupation or the day of adult eclosion produced females that did not oviposit within 30 d of eclosion.