Bryobia praetiosa Koch Clover bryobia mite

This generally abundant species (along with the other species of Bryobia cited below) was once considered part of a complex of closely related biological races. Former members of this complex are structurally very similar, but there are noticeable differences in their habits and life-cycles. The clover bryobia mite infests clover (and many other legumes), grasses and various herbaceous plants; in glasshouses, damage is often caused to the leaves of cucumber plants. Especially in the early spring, the mites frequently invade buildings, where eggs may be laid; the mites also aggregate during the spring and summer on sunny window-sills and on recently constructed brick walls, where they also shelter in cracks and crevices. Infestations are particularly common in weedy, overgrown sites. Leaf injury on host plants varies from speckling to an overall bronzing or silvering and may result in premature leaf-fall; bryobia mites do not produce webbing (cf. fruit-tree red spider mite, Panonychus ulmi, p. 266; two-spotted spider mite, Tetranychus urticae, p. 267).


Mites produced from eggs deposited in the late summer or autumn develop slowly throughout the winter, and eventually reach the adult stage in the following February or March. Eggs deposited by the overwintered females produce a summer generation of mites, members of which feed on a wide variety of host plants and reach maturity by the autumn. Males are unknown and reproduction is entirely parthenogenetic. Migration to and from host plants is a common feature of bryobia mites and continues throughout the spring, summer and autumn, whenever the mites are active. Also, when about to moult from one growth-stage to another, nymphs usually vacate host plants to seek sheltered situations on nearby trees, walls or other structures, as do mature females when they are about to lay eggs.


Adult female 0.7 mm long, blackish-red or dark reddish-brown; legs pinkish, the first pair very long; body oval and flattened; dorsal setae spatulate (cf. stone mite, Petrobia latens, p. 267). Egg 0.2 mm in diameter, dark red, roughly spherical. Larva reddish-orange, 6-legged. Nymph dark green to brown or dark red.

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