Wrackbed-specialist
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Coelopa frigida
seaweed fly, kelp fly
Coelopa frigida is a seaweed fly and the most widely distributed species in its genus, found on temperate Northern Hemisphere shorelines with stranded algae. Adults are 5–6 mm with dark brown to black bodies, lighter legs, and large translucent wings. The species exhibits a chromosomal inversion polymorphism (αβ system) that generates two distinct size morphs with different developmental rates and life-history strategies. It has become a model organism for studying sexual selection, particularly female choice and sexual conflict, and for investigating the genetic basis of local adaptation through chromosomal inversions.