Geoica setulosa

Identification & Distribution:

Adult Geoica setulosa apterae on their secondary host (grass roots) are light yellowish brown, off-white or pale greenish-grey (see first picture below). The primary rhinaria are transversely elongated; slit-like, or of irregular shape with narrow diverticula. Geoica setulosa dorsal body hairs are pointed, spatulate or fan-shaped.

Adult Geoica setulosa have the anal plate enlarged and extended or displaced dorsally, surrounded on three sides by the U-shaped abdominal tergite 8 so as to form a trophobiotic organ to retain honeydew for collection by ants. The anal plate has long and usually pointed hairs arranged in two longitudinal rows (see second picture above), as well as finer, shorter hairs grouped near their anus (cf. Geoica utricularia which has only scattered, shortish hairs on the anal plate, and not arranged in two rows). The body length of the adult Geoica setulosa aptera is 1.6-2.6 mm. The body length of alatae on the secondary host is 1.8-2.3 mm.

The clarified slide mounts below are of adult viviparous female Geoica setulosa : wingless, and winged.

Micrograph of clarified mounted aptera and alate, courtesy Favret, C. & G.L. Miller, AphID. Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO.

On the primary host, (Pistacia khinjuk) in Iran, Geoica setulosa forms galls at the bases of leaflets. These galls open in late August-October. Emigrant alatae found colonies on roots of grasses (e.g. Agrostis, Briza, Festuca, Holcus), attended by ants. Where the primary host Pistacia khinjuk does not occur (most of the aphid's range), the hairy-tailed pistachio-grass root aphid spends its entire life cycle on grass roots reproducing parthenogenetically, often overwintering in the nests of Lasius flavus. Geoica setulosa is found over much of Europe, and has been introduced to USA.

 

Biology & Ecology:

Geoica setulosa is not uncommon on grass roots in southern Britain, often in the company of other species also living on grass roots - such as various Anoecia species and Teraneura ulmi. Ivens (2012) showed that frequency of alate production was very low in some other subterranean ant tended species including the closely related Geoica utricularia.

In Poland Depa & Wegierek, 2011 only found Geoica utricularia and Geoica setulosa) in the nests of Lasius flavus in moist meadow. Zwo1fer (1958) also found that Geoica setulosa was closely associated with ants, although in breeding experiments the aphids were able to survive without ants.

 

Other aphids on grass roots:

Paul (1977) found at least 16 other aphid species recorded on grass roots in Britain: Anoecia corni, Anoecia furcata (= A. nemoralis), Anoecia major, Anoecia (Paranoecia) pskovica Mordvilko, Anoecia vagans (= Anoecia willcocksi), Anoecia zirnitsi, Aploneura lentisci, Baizongia pistaceae (=Pemphigus cornicularius), Forda formicaria, Forda marginata, Geioca setulosa, Geioca utricularia, Paracletus cimiciformis, Rhopalosiphum insertum, Smynthurodes betae and Tetroneura ulmi.

 

Damage and control

Geoica aphids feeding on grass roots can be a major problem on golf courses because the Lasius ants that tend the aphids tend to construct nest mounds on the greens (Maier & Potter, 2005).

Acknowledgements Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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 Depa, L. & Wegierek, P. (2008). Ant-root aphid relations in different plant associations. Polish Journal of Entomology 77, 151-163.  Full text Ivens, A.B.F. et al. (2012). Reproduction and dispersal in an ant-associated root aphid community. Molecular Ecology  Full text Maier, R.M. & Potter, D.A. (2005). Factors affecting distribution of the mound building ant Lasius neoniger (Hymenoptera: Formicidae) and implications for management on golf course putting greens. Journal of economic entomology 98(3), 891-898. Abstract Paul, R.G. (1977). Aspects of the biology and taxonomy of British myrmecophilous root aphids. PhD thesis. Imperial College, London. Full text Zwolfer, H. (1958). Zur Systematik, Biologie und Okologie unterirdisch lebender Aphiden (Homoptera, Aphidoidea). Z. angew. Ent. Part I. 40(2): 182-221. Part II. 40(4): 528-575. Part III. 42(2): 129-172. Part IV. 43(I): 1-52.