Insect neurobiology: What to do with conflicting evidence?

Sensory systems gather information from the environment so the nervous system can formulate appropriate responses. But what happens when sensory information is inconsistent? A new study demonstrates how flies respond to incompatible visual evidence of their own motion.

Carbon dioxide and blood-feeding shift visual cue tracking during navigation in Aedes aegypti mosquitoes.

Haematophagous mosquitoes need a blood meal to complete their reproductive cycle. To accomplish this, female mosquitoes seek vertebrate hosts, land on them and bite. As their eggs mature, they shift attention away from hosts and towards finding sites to lay eggs. We asked whether females were more tuned to visual cues when a host-related signal, carbon dioxide, was present, and further examined the effect of a blood meal, which shifts behaviour to ovipositing. Using a custom, tethered-flight arena that records wing stroke changes while displaying visual cues, we found the presence of carbon dioxide enhances visual attention towards discrete stimuli and improves contrast sensitivity for host-seeking Aedes aegypti mosquitoes. Conversely, intake of a blood meal reverses vertical bar tracking, a stimulus that non-fed females readily follow. This switch in behaviour suggests that having a blood meal modulates visual attention in mosquitoes, a phenomenon that has been described before in olfaction but not in visually driven behaviours.

Mosquito flight: Escaping attacks in dim light.

To avoid fast attackers, animals must move somewhere their pursuer cannot follow or does not expect. A new study shows that female mosquitoes of either a diurnal or a nocturnal species each exhibit a distinct escape strategy matched to the light level they experience as they hunt for blood.

Not Just from Blood: Mosquito Nutrient Acquisition from Nectar Sources.

Anthropophilic female mosquitoes are well known for their strong attraction to human hosts, but plant nectar is a common energy source in their diets. When sugar sources are scarce, female mosquitoes of some species can compensate by taking larger and more frequent blood meals. Male mosquitoes are exclusively dependent on plant nectar or alternative sugar sources. Plant preference is likely driven by an innate attraction that may be enhanced by experience, as mosquitoes learn to recognize available sugar rewards. Nectar-seeking involves the integration of at least three sensory systems: olfaction, vision and taste. The prevention of vector-borne illnesses, the determination of the mosquitoes' ecological role, and the design of efficient sugar-baited traps will all benefit from understanding the molecular basis of nectar-seeking.