Diel rhythms and sex differences in the locomotor activity of hawkmoths

Abstract

Circadian patterns of activity are considered ubiquitous and adaptive, and are often invoked as a mechanism for temporal niche partitioning. Yet, comparisons of rhythmic behavior in related animal species are uncommon. This is particularly true of Lepidoptera (butterflies and moths), in which studies of whole-animal patterns of behavior are far outweighed by examinations of tissue-specific molecular clocks. Here, we used a comparative approach to examine the circadian patterns of flight behavior in Manduca sexta and Hyles lineata [two distantly related species of hawkmoth (Sphingidae)]. By filming isolated, individual animals, we were able to examine rhythmic locomotor (flight) activity at the species level, as well as at the level of the individual sexes, and in the absence of interference from social interaction. Our results confirmed classic descriptions of strictly nocturnal behavior in M. sexta and demonstrated a dramatically different activity pattern in H. lineata. Furthermore, we showed distinct species and sex-specific differences in the maintenance of the endogenous rhythm under conditions of constant darkness. In both species, female activity peaked in advance of males whereas male activity coincided with periods of female sexual receptivity. This suggests a role for circadian patterns of locomotor activity in synchronizing periods of sexual receptivity between the sexes.

From dusk till dawn: camera traps reveal the diel patterns of flower feeding by hawkmoths

“…d–f). Similar qualitative observations have been made by other field researchers (Table S1) and laboratory studies have shown that the short‐tongued hawkmoth Hyles lineata exhibits crepuscular flight rhythms (Broadhead et al ., ), in contrast to the long‐tongued hawkmoth Manduca sexta which exhibits flight activity throughout the night (Hoballah et al ., ; Broadhead et al ., ).…”

“…Information on the diel activity patterns of flower‐visiting animals is essential for understanding the ecology of pollination mutualisms (Stone et al ., ; Hoballah et al ., ; Broadhead et al ., ). However, there is little verified information regarding the activity patterns of nocturnal flower‐visiting insects, such as hawkmoths, as it is notoriously difficult to observe them in a manner that does not affect their behaviour, and because human stamina for all‐night observations is limited.…”

“…It has not been clear whether these represent primary or secondary peaks in activity and whether there is variation in activity patterns among different hawkmoth functional groups. There are also some data on general activity rhythms of hawkmoths from laboratory studies (Hoballah et al ., ; Broadhead et al ., ) and light‐trapping (Beck & Linsenmair, ; de Camargo et al ., ), but it has been uncertain whether these data reflect actual patterns of periodicity of flower feeding in the wild.…”

Light environment drives evolution of color vision genes in butterflies and moths

“…But it often fails for crepuscular species, and species that fly during the night and the day ("both"). For example, even though Manduca sexta is often considered crepuscular, one study has found it is almost entirely nocturnal when compared to Hyles lineata, which is active both during the night and day 75 .…”

Hawkmoth flight in the unsteady wakes of flowers

“…Flying animals rely on maneuverability to survive in unsteady environments whether evading predators, finding mates, or foraging for food (Dudley 2002b, Sprayberry & Daniel 2007, Broadhead et al 2017). As these animals actively move through their environments, locomotion depends on interactions between their body and the surrounding fluid to produce necessary forces and torques.…”