Boreus hyemalis is a very small insect (body length of 3-5 mm) with long legs and downward pointing beak (mouthparts at the end). It is a yellow-brown colour with dark head (no ocelli), antennae and pronotum. The male genital capsule is swollen but not to the extent as Panorpa species. The female has a pale ovipositor. This species is strongly sexually dimorphic. The female has vestigial wings, but those of the males are modified as spines, serrated on the inner edge, to support the female who sites on his back during mating.
The adults are present during winter (active October to April).
Widely distributed in England, Wales and Scoltland, but not recorded in Ireland.
Small size with modified wings, males spine-like, serrated on the inner edge, and females very short. Ocelli are absent. Females with a distinctive ovipositor, male genital capsule is somewhat swollen, however not as dramatically as Panorpa species. Callipers in the male are curved (lateral view).
A. Male Boreus hyemalis close-up. Photograph: Gilles San Martin (CC-BY-SA 2.0)
B. Male Boreus hyemalis. Photograph: lopinga74 (CC-BY-NC)
C. Male Boreus hyemalis head. Photograph: Gilles San Martin (CC-BY-SA 2.0)
D. Female Boreus hyemalis. Photograph: Gilles San Martin (CC-BY-SA 2.0)
Modifications: images have been compiled and text added
The snow flea is unique in being mature during winter. While the larvae are active during late spring and the summer, the adult is active from October - April, with a peak of activity in November and December when it can be seen walking across snow-covered ground, especially in upland areas.
Heathland, moorland or woodland, often seen crawling over moss or in upland areas snow-covered ground