Males become stuck in females after copulation; ca. 50% of such matings exhibit this phenotype. sk¹ males not infrequently are able to disengage eventually on their own; if so, appendages of their terminalia are held in aberrantly protruding positions. A stuck vs. non-stuck mating result is stochastic (as opposed to being a pure penetrance problem, as it were), given that (for example) re-testing a non-stuck case can readily lead to stuck outcome in a subsequent mating. Mutant male-female pairs are more difficult to separate (by vortexing) than are normal copulating pairs. Females unaffected by the genetic variant(s).

Males become stuck in females after copulation; ca. 78% of such matings exhibit this phenotype. There is anatomical abnormality in the strain (near time of isolation): affected males showing narrowing of abdomen. If mutant males are unable to withdraw after copulating, he and the female die within a few days (14% as mortality frequency for mated pairs).