Female Sexual Signaling in a Capital Breeder, the European Glow-Worm Lampyris noctiluca

Abstract

Theory predicts that because costs constrain female sexual signaling, females are expected to have a low signaling effort that is increased with passing time until mating is secured. This pattern of signaling is expected to result from females balancing the costs associated with a higher than optimal signaling effort and those costs associated with a low signaling effort that increase the likelihood of delayed mating. We tested whether this prediction applies in the common glow-worm Lampyris noctiluca (Coleoptera, Lampyridae), a capital breeding species in which females glow at night to attract males. Contrary to predictions, we found that the duration of female sexual signaling significantly decreased with time. Moreover, when females experienced multiple light/dark cycles within 24 h, both signaling duration and intensity significantly decreased. These results imply that females attempt to signal as much as possible at first, with the decrease in signaling duration and intensity likely being due to female resource depletion. Because in capital breeding females the costs of a delayed mating are likely greater than the costs of sexual signaling, females should mate as soon as possible and thus always invest into signaling as much as possible.

Blinded by the Light: Artificial Light Lowers Mate Attraction Success in Female Glow-Worms (Lampyris noctiluca L.)

“…An extended glowing period has several costs for females. First of all, it has an energy cost as glow-worms are capital breeders and cease to feed once adulthood is reached and then rely on the resources built up during their larval stage [26,33,45]. An extended glowing period has indeed a cost on fecundity as the quantity of eggs decreases with time [26,46].…”

“…First of all, it has an energy cost as glow-worms are capital breeders and cease to feed once adulthood is reached and then rely on the resources built up during their larval stage [26,33,45]. An extended glowing period has indeed a cost on fecundity as the quantity of eggs decreases with time [26,46]. It has even been hypothesised that females can use their unlaid eggs as a direct energy source [47].…”

“…After mating, the female lays eggs and dies [21,24]. If a female does not succeed to attract a mate, she will glow again the next nights, remaining at the same location until she is found by a male, or dies [26]. During the day, adult females hide in the forest litter or under the vegetation [21,27].…”

Behavioral responses of bioluminescent fireflies to artificial light at night

“…L. noctiluca females that never glow are significantly less likely to attract nearby males (De Cock et al, 2014), while those that glow over multiple evenings likely do so only because they remain unmated (Tyler, 2002). Even if these females do eventually mate, delays are energetically costly: glow-worms are capital breeders that rarely feed as adults (Wing, 1989;Tyler, 2002), and the energy they require for self-maintenance and bioluminescence depletes over time (Baudry et al, 2021). Some of this energy comes from metabolized eggs (Wing, 1989), steeply reducing fecundity (Horne et al, 2017;Hopkins et al, 2021).…”

Mating status affects female choice when females are signalers

“…Through signaling, females attract males and thus affect male availability. In the extreme case of non‐flying females, like glow‐worms (Baudry et al, 2021 ; Elgert et al, 2021 ; Hopkins et al, 2015 ; South et al, 2011 ), praying mantids (Maxwell et al, 2010 ), or wingless moths (e.g., Roelofs et al, 1982 ; Wong et al, 1984 ), signaling is often crucial to secure a mate. The more males a female attracts, the higher her chance for mating and the more options to choose a mate.…”