|scientific name Capnia vernalis |
Larger, warmer rivers.
Adults emerge from February to April.
This small (length = 4.5 to 6.5 mm for males and females respectively) winter stonefly has the male ninth sternum produced posteriorly into a bluntly pointed subanal plate with an elongate process at the tip lying between the subanal lobes. The elongate process has a second acute anterior projection dorsal to the sternum. Subanal lobes are each subacute and marked off from the sternum by a deep notch. The supra-anal process is extended forward to the hind margin of the ninth tergum; its distal one-third is narrower than the proximal two-thirds, and the tip is pointed. Female subgenital plate has a strongly sclerotized posterior lip about one-third the width of the sternum. The sclerotized floor of the genital tract is visible through the exoskeleton anterad to the posterior lip of the subgenital plate. Sterna 7 and 8 are connected by a narrow sclerotized bridge.
Eggs are laid in spring, hatch, and nymphs diapause throughout summer. Nymphal development occurs throughout fall and winter.
There are no major concerns.
Nymphs are detrivorous.
In Alberta, the species is known from the Saskatchewan River system. Capnia vernalis is widespread and common in North America, ranging from British Columbia to Quebec.
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