A dance on the snow: the mating of Chionea alexandriana (Diptera: Limoniidae)

• Published in: Journal of the Entomological Society of British Columbia 2021-12, Vol.118, p.71-75
• Main Authors: Cannings, R A, Kelly-Mcarthur, B
• Format: Article
• Language: English
• Subjects: Abdomen; Adults; Air temperature; Chionea alexandriana; Clearings (openings); Conifers; Copulation; Dance; Females; Forests; Hardwoods; Males; Museums; National parks; Pine trees; Roads; Snow
• ISSN: 0071-0733; 1929-7890

The site is generally forested but for roadways and small clearings around the dwelling and, although some observations were made on snow near the house, most were from forest-edge habitat, similar to that of the adjacent natural forest. [...]we prefer to document the predominant trees at the site: the forest consists of mixed conifers, mainly Picea engelmannii Parry ex Engelmann, Pinus contorta Douglas ex Loudon, Pseudotsuga menziesii (Mirbel) Franco, and Thuja plicata Donn ex D. Don, and hardwoods such as Betula papyrifera Marshall, Populus balsamifera Linnaeus, and P. tremuloides Michaux. The flies usually walked on snow when the air temperature was -4 °C to -5 °C, but once at -6 °C. This compares well to the temperatures measured during the snow walking of the European C. araneoides Dalman by Hågvar (1971): mostly -4 °C to -5 °C and sometimes as low as -6 °C. Chapman (1954) found C. alexandriana and other species active on snow mainly between 0 °C and -4 °C. All our observations were made on overcast days, agreeing with Byers and many observers he cites, who emphasise that Chionea is almost always seen late in the day, in the evening, or on cloudy days, and appears to avoid strong light. During copulation, as seen in Figure 4, the male approaches the female from behind, supported mainly by the hind legs; his abdomen is curved forward, ventral side up; the gonocoxites grasp the female's hypogynial valves, which slide under the epandrium, and the gonostyli grip the pleural membrane of segment 7.