Abstract
We report an extreme morphological difference betweenDrosophila sechelliaand related species of the pattern of hairs on first-instar larvae. On the dorsum of most species, the posterior region of the anterior compartment of most segments is covered by a carpet of fine hairs. InD. sechellia,these hairs have been lost and replaced with naked cuticle. Genetic mapping experiments and interspecific complementation tests indicate that this difference is caused, in its entirety, by evolution at theovo/shaven-babylocus. The pattern of expression of theovo/shaven-babytranscript is correlated with this morphological change. The altered dorsal cuticle pattern is probably caused by evolution of the cis-regulatory region ofovo/shaven-babyin theD. sechellialineage.