Mass movement of “invisibles”: We know a lot about vertebrate migrations globally. However, the majority of animals that live on this planet are invertebrates, and we know very little about their movements. Hu et al. monitored the migration of large and small insects over the southern United Kingdom for a decade. They found that more than a trillion insects move across this region annually. The movement of such a large biomass has considerable impacts on the ecosystems between which the insects migrate. Science , this issue p. 1584

Not at the Mercy of the Wind: How can insects that migrate at high altitudes on fast-moving winds influence their direction of migration, when wind speeds typically exceed their self-propelled air speeds by a factor of three or four? Using automated vertical-looking entomological radar systems, Chapman et al. (p. 682 ) show that compass-mediated selection of favorable tailwinds, and partial correction for crosswind drift, are widespread phenomena in migrant insect species. Specialized flight behaviors have decisive influence on the migration pathways achieved by insects. Thus, contrary to popular belief, migrant insects are not at the mercy of the wind.

Radar has been used to study insects in flight for over 40 years and has helped to establish the ubiquity of several migration phenomena: dawn, morning, and dusk takeoffs; approximate downwind transport; concentration at wind convergences; layers in stable nighttime atmospheres; and nocturnal common orientation. Two novel radar designs introduced in the late 1990s have significantly enhanced observing capabilities. Radar-based research now encompasses foraging as well as migration and is increasingly focused on flight behavior and the environmental cues influencing it. Migrant moths have been shown to employ sophisticated orientation and height-selection strategies that maximize displacements in seasonally appropriate directions; they appear to have an internal compass and to respond to turbulence features in the airflow. Tracks of foraging insects demonstrate compensation for wind drift and use of optimal search paths to locate resources. Further improvements to observing capabilities, and employment in operational as well as research roles, appear feasible.