Hormonal modulation of larval begging and growth in the burying beetle Nicrophorus vespilloides

Recent studies on birds show that two steroid hormones, testosterone and corticosterone, stimulate nestling begging and growth. Here, we seek to investigate whether juvenile hormone, a major regulatory insect hormone, has similar effects on larval begging and growth in insects. To this end, we experimentally elevated larval juvenile hormone levels by topical application of methoprene, a potent and stable synthetic juvenile hormone analogue, and monitored effects on larval begging and growth in the burying beetle Nicrophorus vespilloides. In this species, larvae feed partly by begging for predigested carrion from parents and partly by self-feeding. We showed that elevated juvenile hormone levels stimulate larval begging, suggesting that juvenile hormone in insects could have a similar function to that of testosterone and corticosterone in birds. We also showed that elevated juvenile hormone levels have a negative effect on larval growth and that this negative effect occurs regardless of whether larvae forage by begging or by self-feeding. This finding shows that the effects of juvenile hormone on larval growth are independent of the effects on begging, suggesting that the mechanisms by which juvenile hormone affects offspring growth in insects differ from those by which testosterone and corticosterone affect growth in birds.