Anystis baccarum

Identification & Distribution

Anystis baccarum mites (see two pictures below) are orange-red in colour, long legged and very mobile. They range in size from 1.0 to 1.5 mm in diameter and are important predators in apple orchards (cf. the orchard mite pest Panonychus ulmi - the European fruit tree red spider mite - which is much smaller at 0.4 mm in diameter, is relatively sedentary and is only found on the underside of leaves). Cuthbertson et al. (2014) summarizes the key characteristics based on Meyer & Ueckermann (1987) as follows:

• On the dorsum, the prodorsal shield is almost rounded anteriorly and indented posteriorly, bearing two pairs of long setae and a pair of sensilla. The anterior margin of the idiosoma has also a pair of sensilla. Two pairs of eyes are located postero-lateral to the prodorsal shield.
• The legs of Anystis baccarum are densely covered with short smooth setae. Each tarsus terminates in two claws, and an empodium with brush-like setae is present.
• On the gnathosoma, the palptibia has three claws and the palptarsus bears four small solenidia. There are many long serrated setae of which the terminal setae is the longest. The two chelicerae each contain two setae. The distal half of the reticulated peritremes are flared.

There are at least 18 species of Anystis mites. Anystis baccarum is the best known species of that genus, and is considered an important generalist predator in cereals and orchards. It is popularly known as the "whirligig mite" owing to its spiral-like running fashion. Anystis agilis is a general predator of insect pests in American vineyards and Anystis wallacei was introduced (unsuccesfully) to Australia in an attempt to control redlegged earth mite (Halotydeus destructor).

Biology & Ecology

Male Anystis baccarum have not been recorded, and females reproduce by parthenogenesis. Eggs are laid in clusters numbering between 15 & 24 under bark and in soil litter.

In Britain we have found what appears to be Anystis baccarum predating the ivy aphid Aphis hederae (see picture below).

We have also found it in coniferous woodland predating the grey waxy pine needle aphid Schizolachnus pineti (see picture below).

Note, in both the above cases, the exudations from the aphid's siphunculi. Such exudations would normally indicate release of an alarm pheromone, but in this case there was no indication of any response from the other aphids in its colony. Waxy pine needle aphids show what is called "contact clustered aggregation" - in which the bodies of individuals are in mutual contact in rows along the pine needles. Schizolachnus pineti use touch to communicate the presence of a predator, and there is no evidence for an alarm pheromone (Kidd, 1982).

Interestingly, other predators are seldom observed attacking either the ivy aphid or the waxy pine needle aphid. The former is protected by toxins from its foodplant, and the latter is protected by its wax covering. Perhaps whirligig mites are more successful predators when they are not having to compete with a host of other predators, which may well predate the whirligig mites along with their normal prey.

We have also observed an Anystid mite predating an unidentified aphid on bulrush (Typha).

Biological control of Aphids

Anystis baccarum has been shown to play a possible role in the biological control of aphids in cereals (Sitobion avenae). It has also been found feeding on the apple-grass aphid Rhopalosiphum oxyacanthae, and is considered a potential biocontrol agent in UK apple orchards (Cuthbertson & Murchie, 2008).

In Canada, Grobler 1962 found that Anystis agilis was an important predator of Schizolachnus piniradiatae, causing a 30-50% mortality among overwintering eggs.

Acknowledgements For aphids we have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References  Cuthbertson, A.G.S. et al. (2003). Detection of Rhopalosiphum insertum (apple grasss aphid predation by the predatory mite Anystis baccarum using molecular gut analysis. Agricultural & Forest Entomology 5, 219-225. Full text Cuthbertson, A.G.S. & Murchie, A.K. (2005). Anystis baccarum - an apple orchard assassin. Biologist 52 (6), 324-327. Full text Cuthbertson, A.G.S. & Murchie, A.K. (2008). Anystis baccarum - a potential biocontrol agent in UK apple orchards. In: Proceedings of the Third International Symposium on Biological Control of Arthropods, Christchurch, New Zealand. Full text Cuthbertson, A.G.S. et al. (2014). Anystis baccarum: An important generalist predatory mite to be considered in apple orchard pest management strategies. Full text Grobler, J.H. (1962). The life history and ecology of the woolly pine needle aphid, Schizolachnus pini-radiatae (Davidson) (Homoptera: Aphididae). The Canadian Entomologist 94(1), 35-45. Abstract Kidd, N.A.C. (1982). Predator avoidance as a result of aggregation in the Grey Pine Aphid, Schizolachnus pineti. Journal of Animal Ecology 51(2), 397-412. Full text Meyer, M.K.P.S. & Ueckermann, E.A.A. (1987). A taxonomic study of some Anystidae (Acari: Prostigmata). Entomol. Mem.. 68, 1-37. Abstract