Photoperiodic induction of adult reproductive diapause in the ladybird beetle Cycloneda munda (Coleoptera: Coccinellidae)

Abstract

The developmental response and the induction and duration of adult hibernal diapause in a North American population of Cycloneda munda (Say) (collected at 38°N, 84.5°W) was determined by rearing individuals at four photoperiods (L : D 16 : 8, 14 : 10, 12 : 12, and 10 : 14) at 22°C. Preimaginal development of C. munda individuals was slower at L : D 10 : 14 than at three longer photoperiods. No C. munda females reared at L : D 16 : 8 entered diapause, 5% of females at L : D 14 : 10 were in diapause, whereas shorter photoperiods (L : D 12 : 12 and 10 : 14) induced diapause in 84% and 100% of females. Cycloneda munda females demonstrated a long-day response to photoperiod, similar to that observed in several other species of predaceous Coccinellidae that diapause as adults. * This paper was contributed to a virtual special issue in memory of Ivo Hodek, a long-time editor of the European Journal of Entomology, who died on June 11, 2021, shortly after his ninetieth birthday. INTRODUCTION Interactions between native and non-native species of predaceous Coccinellidae are infl uenced by a number of factors, including predator-prey and pathogen-host interactions (Cottrell & Shapiro-Ilan, 2008; Colvin & Yeargan, 2014; Jackson et al., 2017), intraguild interactions (Bahlai et al., 2015), phenotypic plasticity (Hodek & Michaud, 2008), and the seasonal occurrence and phenology of these species (Li et al., 2021). In a 5-yr study of adult Coccinellidae in tree habitats in central Europe Honek et al. (2015) documented that the native species Adalia decimpunctata was the most abundant species in spring, however the non-native Harmonia axyridis was consistently the most abundant species in late summer. Quantifi cation of differences in seasonal occurrence when examining communities of Coccinellidae that include native and non-native species is an important consideration for an understanding of the interactions of these species (Honek et al., 2015). Photoperiod infl uences the seasonal biology, particularly the induction of adult reproductive diapause, in many insect species, including predaceous Coccinellidae (Tauber et al., 1986; Hodek, 2012a, b; Tougeron, 2019). This area of research was of particular interest for Ivo Hodek, who elucidated and synthesized a large body of research on the effects of photoperiod and its interactions with temperature and food availability on the seasonal phenology of several species of ladybird beetles (e.g., Hodek, 1967, 2012a, b). One long-standing species of interest for Ivo Hodek was the seven spotted ladybird beetle, Coccinella septempunctata. Starting in the early 1960s and continuing into the 21st century, he published on the factors infl uencing the diapause and seasonal phenology of this widely distributed predatory species Eur. J. Entomol. 119: 148–151, 2022 doi: 10.14411/eje.2022.016