Journal of the Kansas Entomological Society
The head capsule of the 1st larval instar of Coelioxys octodentata and Coelioxys sayi is delicate, whereas the head capsules of the 2nd and 3rd instars are heavily sclerotized with huge mandibles. Brevity of the 1st stadium and delicacy of 1st instar exuvia probably caused the 1st instar to have been overlooked by previous workers. In the 3rd instar, males of C. sayi have mandibles that are significantly shorter than those of both C. sayi and C. octodentata females and significantly longer than those of C. octodentata males. The 4th and 5th instars are progressively more similar to those of related bees such as Megachile. Females in the 4th instar have a more pronounced shoulder on the outer surface of the mandible than do 4th instar males. Sexes are separable in the 4th and 5th instars by a transverse slit on the 12th sternite of the male.
Baker, J. R., "Development and Sexual Dimorphism of Larvae of the Bee Genus Coelioxys" (1971). An. Paper 267.
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