quality:correction, structural:summarization, linguistic:voice_change
Solitary and gregarious phases

One of the greatest differences between the solitary and gregarious phases is behavioural. The gregaria nymphs are attracted to each other, this being seen as early as the second instar. They soon form bands of many thousands of individuals. These groups behave like cohesive units and move across the landscape, mostly downhill, but making their way around barriers and merging with other bands. The attraction between the insects involves visual and olfactory cues. The bands seem to navigate using the sun. They pause to feed at intervals before continuing on, and may cover tens of kilometres over a few weeks.

Locusts in the gregarious phase differ in morphology and development. In the desert locust and the migratory locust, for example, the gregaria nymphs become darker with strongly contrasting yellow and black markings, they grow larger, and have a longer nymphal period; the adults are larger with different body proportions, less sexual dimorphism, and higher metabolic rates; they mature more rapidly and start reproducing earlier, but have lower levels of fecundity.

The mutual attraction between individual insects continues into adulthood, and they continue to act as a cohesive group. Individuals that get detached from a swarm fly back into the mass. Others that get left behind after feeding take off to rejoin the swarm when it passes overhead. When individuals at the front of the swarm settle to feed, others fly past overhead and settle in their turn, the whole swarm acting like a rolling unit with an ever-changing leading edge. The locusts spend much time on the ground feeding and resting, moving on when the vegetation is exhausted. They may then fly a considerable distance before settling in a location where transitory rainfall has caused a green flush of new growth.