Complex sentence: In contrast to mayflies, which are small and usually live only 24 hours as adults because they do not eat, fishflies are quite large, their wing span being from 2.5 to 3.
Split into simpler sentences: In contrast to mayflies, which are small and usually live only 24 hours as adults because they do not eat. Fishflies are quite large, their wing span being from 2.5 to 3.