Figure 2.

Female larviposition preferences. (a) Absolute number of larvae deposited during experiments. Grey: total number of larvae deposited across cages per experiment. Yellow: number of larvae deposited in stimulus trays, rather than on the floor. Larvae deposited on the floor were not included in the analysis. (b) Choice index for larvipositing on trays versus on the floor. The choice index was corrected for surface area. Across experiments females prefer to larviposit on trays. (c) In the ‘substrate’ condition, females were offered the choice between natural-colour sand and leaf litter as larviposition substrate. (d) The preference index (PI) for the ‘substrate’ condition shows a strong preference for leaf litter (median PI = 0.817). (e) A ridge histogram of larval count for each stimulus in the ‘substrate’ condition shows a significantly higher larval count in leaf litter (p < 0.001, Wilcoxon rank-sum test). (f) In the ‘pentadecane’ condition, females chose between the proposed larval pheromone n-pentadecane and the solvent paraffin oil as a control stimulus. (g) PI for the ‘pentadecane’ condition shows no preference for n-pentadecane. (h) The distributions of larval count in the stimulus and control trays strongly overlap. (i) In the ‘naturalistic’ condition, females chose between sand conditioned with 20 1-day-old pupae, and unconditioned sand. (j) PI for the ‘naturalistic’ condition shows no preference for conditioned sand. (k) The distributions of larval count in conditioned versus unconditioned sand strongly overlap. (l) Conditional effects predicted by a Bayesian model of female choice. The model supports a preference only in the ‘substrate’ condition (estimated median = 0.906, s.e. = 0.02) but not in the ‘pentadecane’ or ‘naturalistic’ conditions (estimated medians 0.502 and 0.5125, respectively). (m) In a subset of experiments, the cage had one dark wall. The PI for cage side shows that females depositing in trays do not have a preference for the darker side of the cage (no difference from normal distribution, mean = 0, s.d. = 1, Kolmogorov–Smirnov test), but females depositing on the floor prefer the darker half of the floor (median PI = 0.402; difference from normal distribution, mean = 0, s.d. = 1: p ≪ 0.001, Kolmogorov–Smirnov test).