MORPHOMETRIC VARIABILITY IN LARVAE OF THE ANTARCTIC FLY, BELGICA-ANTARCTICA (DIPTERA, CHIRONOMIDAE)

Morphometric variability is examined in the larval head capsule of the midge B. antarctica Jacobs. This species is the southernmost free-living holometabolous insect and occurs over about a 650 km range on the western side of the Antarctic Peninsula. Highly significantly differences were found between samples and between sexes for 9 larval head capsule characters. No morphometric effect was found due to chromosomal inversion heterozygosity. The expression of sexual dimorphism varied greatly between samples. Some samples exhibited no sexual dimorphism whereas others exhibited highly complex patterns of sexual dimorphism. Attempts to relate morphometric variability to geographic and ecological parameters met with only limited success. No correspondence was noted between the classification of samples based on inversion heterozygosity and that based on larval morphology.