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Eriosomatinae : Fordini : Forda formicaria


Forda formicaria

Pistachio-grass root aphid

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

Identification & Distribution

Adult apterae of Forda formicaria vary in colour from off-white to dull yellow to various shades of dark green or bluish-green, often with a slighly darker medio-dorsal stripe. The third antennal segment is about the same length as the fourth and fifth segments combined (cf. Forda marginata, which has the third antennal segment longer than the fourth and fifth segments combined). The primary rhinarium on the base of antennal segment 5 is very large, transversely long and extending around the segment. It is 4-5 times larger than the primary rhinarium on antennal segment 4 (cf. most other Forda species, which have the primary rhinarium on the base of antennal segment 5 almost circular and less than 2.5 times larger than that on antennal segment 4). The posterior abdomen has, at most, one curved dark cross-band (cf. Forda marginata, which often has two or more curved dark cross-bands on the posterior abdomen). There are no siphunculi. The body length of adult Forda formicaria apterae is 1.9-3.3 mm.

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Alates migrating from their primary host have a black head and thorax and a green-yellow abdomen. The third antennal segment has 25-42 secondary rhinaria and is conspicuously hairy.

In the Mediterranean region and south-west Asia, Forda formicaria forms half-moon-shaped galls on its primary host Pistacia species (pistachio). Alates leave the galls in September to November, and move to the roots of numerous grasses and cereals where they found colonies. In many other parts of the world (northern Europe, parts of Asia and North America), host alternation (and sexual reproduction) have been lost, and they live on the roots of grasses all year round. Forda formicaria are always attended by ants, and often live within ants' nests.


Other aphids on same host

Blackman & Eastop list 66 species of aphid as feeding on grass roots (Poaceae) worldwide (Show world list).

Paul (1977) found at least 16 other aphid species recorded on grass roots in Britain (Show British list).


Our particular thanks to David Fenwick for his images of Forda formicaria.

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


  • Paul, R.G. (1977). Aspects of the biology and taxonomy of British myrmecophilous root aphids. PhD thesis. Imperial College, London. Full text