Trombidiidae

Allothrombium fuliginosum (Hermann, 1804)

Biology

The female of this mite  mates in the autumn or spring. It spends winter sheltered in the ground.
When the summer weather arrives, if fertilized, she lays 700-1500 spherical eggs in a crack in the bark or the ground.
The eggs then hatch, giving rise to larvae. The larva has then to find an aphid host to attach itself as an ectoparasite. They have one week to do this, indeed if they fail they die. Once they find the host, the larva fixes itself indiscriminately on any part of the aphid’s body. In 3 or 4 days it extracts enough food to continue and accomplish its development.
As for the aphid, its development is blocked and it soon dies.
The parasite subsequently detaches itself, letting itself down to the ground to prepare its first metamorphosis. After about one month it becomes a “pre-adult” which then feeds abundantly on a wide variety of prey, including aphids.
When autumn arrives, a second metamorphosis occurs. The adult generally emerges, ready to mate, before winter.

Particular characteristics

This small red velvety ball runs around, zigzagging quickly over sun-exposed stones or bark. Of course this species is far less devastating for the aphid than the shock-troop predators like the ladybirds. However, these small bright red blobs seen fixed to the aphids. Even if the role of these Acari is played on a small-scale, they do contribute to aphid population regulation.