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Genus Forda

Pistachio-grass aphids

Species Overview: Genus Forda  Forda formicaria 

Genus Forda [Fordini]

These are medium-sized aphids. On the primary host they live in galls. Thefundatrix initially forms a small temporary gall near the apex of the leaf, but her offspring move to the leaf margin where they form characteristic leaf-edge galls by folding and rolling the leaf margins. Emigrant alates have a dark head and thorax and a pale body. Apterae on the secondary host are often yellowish-white and plump-bodied and are not waxy.

About 10 species host alternating (in the Mediterranean region and south-west Asia) from pistacchio (Pistacia) to the roots of grasses and cereals. Outside the range of Pistacia, several species are known only from their secondary hosts. They are attended by ants on the secondary host and often live in ants' nests.

 

Forda formicaria (Pistacchio-grass root aphid)

Forda formicaria apterae vary in colour from off-white to dull yellow to various shades of dark green or bluish-green. 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 (this distinguishes it from most other Forda spp. 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 body length of Forda formicaria is 2-3 mm.

 

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Alates migrating from the primary host have a black head and thorax and a green-yellow abdomen.

In the Mediterranean region and south-west Asia, Forda formicaria forms half-moon-shaped galls on its primary host Pistacia spp. (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.

Acknowledgements

We especially thank David Fenwick for the images of Forda formicaria.

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

  •  Blackman, R.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.