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Geoica utricularia

Short-haired pistachio-grassroot aphid

On this page: Identification & Distribution Other aphids on the same host

Identification & Distribution

Geoica utricularia induces a smooth, globular yellowish gall on its primary host Pistacia terebinthus (see first two pictures below). Adult apterae are very plump-bodied, off-white, cream or yellowish, usually with scattered globules of wax. The head, prothorax, appendages and anal region are brownish. Geoica utricularia has no siphunculi (cf. Tetraneura ulmi which has small siphunculi). The anal plate has scattered, shortish, sometimes spatulate or flabellate (=fan-shaped), hairs. They are not arranged in two longitudinal rows (cf. Geoica setulosa which has the anal plate with long and usually pointed hairs arranged in two longitudinal rows). The body length of adult apterae is 1.6-3.0 mm.

Note:
The name Geoica utricularia is conventionally applied to anholocyclic populations of this group on grass roots throughout Europe and in North Africa (Morocco), the Middle East, Central Asia, North America, and China (as subpecies urunquiensis Qiao). However Blackman notes that these populations vary considerably in chaetotaxy (=the arrangement of bristles), particularly of the apical rostral segment, abdominal tergite 8, cauda and anal plate, and it is possible that more than one species is involved, or that the name is being applied incorrectly.

First image above, by permission, copyright Ben van As
Second image above, copyright Houard 1909;
Third image above, by permission, copyright Mariusz Kanturski all rights reserved.

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

Micrographs of clarified mounts courtesy Favret, C. & G.L. Miller, AphID. Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO.

Geoica utricularia alatae have a dark head and thorax and a pale yellowish-green abdomen with dark transverse bars, longer on the more posterior tergites.

On its main primary host, Pistacia terebinthus, in the Mediterranean area and south-west Asia Geoica utricularia usually forms its gall near the base of a leaflet, close to the main vein. Colour, texture and shape seem to vary somewhat with the host species, but on this Pistacia species they are smooth and yellowish with a pinkish tinge. These galls open in July-October. Emigrant alatae found colonies on roots of grasses (such as Agrostis, Avena, Bromus, Deschampsia, Festuca, Hordeum, Lilium, Phleum, Poa), attended by ants.

 

Images above, by permission, copyright Mariusz Kanturski all rights reserved.

Where none of the primary hosts occur (most of the aphid's range), the short-haired pistachio-grassroot aphid spends its entire life cycle on grass roots reproducing parthenogenetically. Geoica utricularia is found throughout Europe and in North Africa, the Middle East, Central Asia and North America.

 

Other aphids on the same host

Primary hosts

Geoica utricularia is found on 4 or 5 Pistacia species (Pistacia chinensis, Pistacia integerrima, Pistacia palaestina (?), Pistacia terebinthus, Pistacia vera).

Blackman & Eastop list 19 species of aphid as feeding on those species of Pistacia worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015) lists 6 as occurring in Britain: Baizongia pistaceae, Forda formicaria, Forda marginata, Geoica utricularia, Paracletus cimiciformis, and Smythurodes betae.

Secondary hosts

Paul (1977) found at least 16 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, Forda formicaria, Forda marginata, Geoica setulosa, Geioca utricularia, Paracletus cimiciformis, Rhopalosiphum insertum, Smynthurodes betae and Tetroneura ulmi.

Acknowledgements

We are extremely gratefulto Ben van As for his picture of the gall on Pistacia terebinthus in Greece, and to Mariusz Kanturski for the excellent images of Geioca utricularia on grass roots in Poland; also to Willem Ellis, bladmineerders.nl, for putting us in touch with Mariusz.

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).

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