Larval Morph Variation in Chlosyne Lacinia (nymphalidae)

Mature larvae of the patch butterfly, Chlosyne lacinia (Geyer), exhibit striking color polymorphism. First described by T. D. A. Cockerell in Edwards (1893) and illustrated by Neck et aI. (1971), the three morphs are as follows: rufa, an all orange or orange-red form; nigra, an all black form; and bicolor, a form basically black as in nigra but with a prominent mid-dorsal row of orange to orange-red blotches whose proximity to each other gives the impression of a stripe. The black pigment is present in the cuticle while the orange pigment is in a deeper layer (hypodermis) that shows through window-like areas of the cuticle devoid of pigment. Laboratory crosses utilizing adults of known larval phenotypes revealed that the larval color polymorphism involves two unlinked autosomal loci (Neck et aI., 1971). At one locus bicolor (B) is dominant to nigra (b). At the second locus rufa (R) is dominant to non-rufa (r). The rufa allele is epistatic to the first locus; no phenotypic expression of the first locus occurs when the rufa allele is present at the second locus. Although there are only three major morphs in this species, a variety of subtypes exists which indicate the influence of genetic modifiers and/or environmental factors. The most common variant is a nigra form with circular light yellow-orange spots of varying intensity at the base of each mid-dorsal spine. This phenotype, named dot, is pictured in Plate ID of Neck et aI. (1971). It may be the same form reported by Cockerell (in Edwards, 1893) and Gorodenski (1969) although the description by Cockerell ("with numerous yellow-white spots") could possibly refer to the super-dot form described below. Nearly all nigra have a small spot at the base of each mid-dorsal spine. (42 of 50 or 84.0% nigra larvae collected 10 September 1972 at Austin were definitely dot; others had very small dot.) In some individuals it is inconspicuous enough to be unnoticed unless critically examined under a dissecting microscope. In other individuals the dot is so large as to create confusion with the bicolor morpho In most cases the dot of the nigra tends towards yellow whereas the block of the stripe in bicolor is more orange. In addition, a black mid-dorsal line present in those larvae is seen in the bicolor larvae only between the orange spots and