Innate olfactory preferences for flowers matching proboscis length ensure optimal energy gain in a hawkmoth

Cost efficient foraging is of especial importance for animals like hawkmoths or hummingbirds that are feeding ‘on the wing', making their foraging energetically demanding. The economic decisions made by these animals have a strong influence on the plants they pollinate and floral volatiles are often guiding these decisions. Here we show that the hawkmoth Manduca sexta exhibits an innate preference for volatiles of those Nicotiana flowers, which match the length of the moth's proboscis. This preference becomes apparent already at the initial inflight encounter, with the odour plume. Free-flight respiration analyses combined with nectar calorimetry revealed a significant caloric gain per invested flight energy only for preferred—matching—flowers. Our data therefore support Darwin's initial hypothesis on the coevolution of flower length and moth proboscis. We demonstrate that this interaction is mediated by an adaptive and hardwired olfactory preference of the moth for flowers offering the highest net-energy reward

Larval sensilla of the moth Heliothis virescens respond to sex pheromone components

Female-released sex pheromones orchestrate the mating behaviour of moths. Recent studies have shown that sex pheromones not only attract adult males but also caterpillars. Single sensillum recordings revealed that larval antennal sensilla of the moth Heliothis virescens respond to specific sex pheromone components. In search for the molecular basis of pheromone detection in larvae, we found that olfactory sensilla on the larval antennae are equipped with the same molecular elements that mediate sex pheromone detection in adult male moths, including the Heliothis virescens receptors 6 (HR6) and HR13, as well as sensory neurone membrane protein 1 (SNMP1). Thirty-eight olfactory sensory neurones were identified in three large sensilla basiconica; six of these are considered as candidate pheromone responsive cells based on the expression of SNMP1. The pheromone receptor HR6 was found to be expressed in two cells and the receptor HR13 in three cells. These putative pheromone responsive neurones were accompanied by cells expressing pheromone-binding protein 1 (PBP1) and PBP2. The results indicate that the responsiveness of larval sensilla to female-emitted sex pheromones is based on the same molecular machinery as in the antennae of adult males