First Record and Ecological Observations on the Eastern Red-winged Blister Beetle (Tricrania sanguinicollis) in Manitoba
By Deanna Dodgson and Robert E. Wrigley |
Website and document preparation by Doug Collicutt |
On March 19, 2021, Deanna noticed a number of red and black beetles crawling slowly over the ground in the Portage Sandhills, south of Portage la Prairie, in south-central Manitoba. This was an unexpected discovery so early in the spring, and in fact there were still patches of snow in low areas. She identified the species as the blister beetle Tricrania sanguinicollis and notified Robert, who visited the site the following day. Over the next couple of weeks, we observed large numbers of live individuals (some mating) as well as dead ones. This is the first report of this species in Manitoba, with the closest records in the Minneapolis area, about 650 km to the southeast. Since this beetle lacks wings and has weak crawling ability (falling over easily and is challenged to right itself), the question arose how did it manage to reach southern Manitoba sandhills, with few suitable sandhill habitats in between.
Further research in the field and the literature revealed that this beetle’s life history is closely synchronized with that of early emerging, ground-nesting, cellophane bees, such as Colletes inequalis. In early spring, the beetle emerges from its burrow as soon as the ground thaws in elevated sandy sites exposed to the sun. The male beetle searches for a mate by crawling over the ground until it finds a female or her pheromone trail to follow, and mating occurs. The female lays fertilized eggs, which hatch in a few days into highly mobile larvae. These attempt to attach to a male bee while on the ground, the latter also having recently emerged from its hibernaculum underground. The bee searches for an emerging female bee, and during copulation, the beetle larva transfers to the female bee, which then gathers pollen and nectar to supply its own eggs laid in its burrow. The successful larva then dislodges from its host in the bee burrow and commences feeding on the bee eggs and possibly the food stores.
Following a number of growth-moults over the summer, the beetle larva enters a pupal stage for the winter, still secluded in the bee’s burrow. It remains in this stage until the ground warms in the spring, and is stimulated to emerge from its pupal case and up onto the surface, where the life cycle is repeated. The beetle is therefore entirely dependent on the bee to provision its young (described as an obligate brood parasitoid). The large number of dead beetles on the sand is evidence that the species does not feed as an adult, and that numerous individuals are killed by freezing temperatures and snow events usual at this time of the year.
We surmise that the beetle dispersed as far north as southern Manitoba via its larvae attached to dispersing bees, as the prairie community replaced the melting Pleistocene glacier. We have now detected the beetle’s and bee’s presence at several sandhill locations distributed from the Portage area west to Shilo.
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