Behav Ecol Sociobiol (2005) 58: 578–586 DOI 10.1007/s00265-005-0947-1 ORIGINAL ARTICLE Jennifer C. Perry · Bernard D. Roitberg Ladybird mothers mitigate offspring starvation risk by laying trophic eggs Received: 5 October 2004 / Revised: 24 January 2005 / Accepted: 19 March 2005 / Published online: 1 June 2005 C  Springer-Verlag 2005 Abstract A large proportion of ladybird beetle (Coleoptera: Coccinellidae) eggs are apparently infertile— they do not develop an embryo and are consumed by larvae hatching within the egg batch. The predicted benefits of egg consumption for larvae are empirically well supported. An important question, however, remains: are these eggs a maternal strategy to feed offspring (i.e., trophic eggs) or did egg eating evolve to exploit unavoidably infertile eggs? We investigated the adaptive value of infertile eggs in lab- oratory experiments with multicoloured Asian ladybirds (Harmonia axyridis). Female H. axyridis were assigned to low and high resource environments for brief intervals; we predicted that tactics to facilitate egg cannibalism, such as infertile egg production and hatching asynchrony, would be adopted in low food environments in which starvation risk for offspring is greater. We conducted two experiments in this manner that provided females with information about resource levels through prey feeding or scent. We also observed female oviposition patterns and tested for infertile egg distributions that departed from random. Females produced 56% more infertile eggs in the low vs. the high food treatment; however, hatching synchrony did not change. We consider a potential confound between information and nutrition state unlikely because ladybirds are well able to tolerate low food for 24 h, the duration of trials, and because females were in good condition when trials began. Results suggest that ladybirds use information from prey encounter to manipulate the proportion of trophic eggs in a manner consistent with the adaptive hypothesis, the first evidence of trophic egg plasticity in a non-eusocial insect. Communicated by M. Elgar J. C. Perry () · B. D. Roitberg Behavioural Ecology Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada e-mail: jperry@zoo.utoronto.ca J. C. Perry Department of Zoology, University of Toronto, Toronto, ON M5S 3G5, Canada Keywords Coccinellidae . Harmonia axyridis . Hatching synchrony . Sibling cannibalism . Trophic eggs Introduction Parents in many species face the problem of high star- vation risk for their offspring. Furthermore, some parents (e.g., most insects) do not interact with their offspring fol- lowing oviposition; hence mothers in this situation are lim- ited to starvation-reduction behaviors that are expressed at the egg production or deposition stage. In the extreme case, a mother’s best option might be to provide food for offspring in the form of eggs themselves (Alexander 1974; Mock and Forbes 1995). Mothers should sacrifice some offspring to others when they gain more offspring from the increased survival of the cannibals than they lose as victims (Crespi 1992)—thus, when offspring star- vation risk is high and eating a sibling provides a large benefit. One way for mothers to ensure that offspring have a sibling to eat is to produce ‘trophic’ offspring that serve as a meal (Alexander 1974). This hypothesis provides a foundation for the study of trophic eggs—non-developing, ovariole-produced structures that are formed to feed offspring (Crespi 1992). In studying hypothesized trophic eggs, then, it is necessary to ask the functional question: is there an adaptive maternal strategy to feed offspring? The alternative hypothesis is that some infertile eggs are un- avoidably produced through some constraint (e.g., sperm limitation), and that offspring are adapted to consume such eggs. In some taxa, the adaptive nature of trophic eggs seems clear; for example, when they have a unique morphology, clearly different from viable eggs (e.g., West and Alexander 1963; Henry 1972), or when parents actively feed them to offspring (e.g., Nakahira 1994; Heying 2001). In ladybird beetles, offspring consume undifferentiated, apparently infertile eggs that occur within their natal egg batch (e.g., Kawai 1978; Osawa 1992). For ladybirds and similar taxa (e.g., Valerio 1977; Frechette