Larval food composition affects courtship song and sperm expenditure in a lekking moth

1. Variation in larval food composition can have far-reaching effects on the adult phenotype of insects. To maximise reproductive output, it is therefore beneficial if insects are able to plastically adapt to nutritional cues in their larval diet. 2. The expression of sexual traits implicated in pre- and postcopulatory sexual selection of the lesser wax moth, Achroia grisella Fabricius, across different rearing environments of varying diet composition was investigated.3. Moths reared on diet with relatively low amounts of carbohydrate, but more protein and fats, had lower survival rates, decreased body mass, and longer development times. Males reared on this diet produced songs with higher pulse pair rates (which are attractive to females) and transferred more sperm per copulation than males reared on the alternative diets. 4. There was no evidence for a trade-off between pre- and postcopulatory traits. Interestingly, individuals with both higher pulse pair rates and more transferred sperm came from the treatment group with higher mortality rates and generally poorer development. The present results suggest that both of these sexual characteristics are developmentally plastic, but that only moths reared on the protein-rich diet were able to benefit from this plasticity.