Genus Jacksonia

Jacksonia [Macrosiphini]

Jacksonia are rather small aphids, much like Myzus except for the unusual shape of the siphunculus. Their antennal tubercles are well developed, rough and broad, but the median frontal tubercle is not developed. There are no marginal tubercles. Jacksonia apterae have no secondary rhinaria whilst alatae have large protuberant secondary rhinaria on antennal segments III-V. The siphunculi are slender, thinnest in the middle, and without a flange.

Only three species are known in the genus Jacksonia: two feed on grasses, and one on bellflowers (Campanula).

Jacksonia papillata (Olive-brown grass aphid)

Adult apterae of Jacksonia papillata are plump oval, little pigmented but appearing brownish- or greenish-ochreous, and lightly dusted with wax on the underside and legs - and sometimes intersegmentally on the first two or three abdominal segments. The entire body cuticle is strongly rugose with large frontal tubercles and scabrous spinules on the head. The antennae are about 0.7 times the body length, with the terminal process 1.7-2.1 times the length of the base of segment VI. The apical segment of the rostrum (RIV+V) is about 1.2 times the length of the second hind tarsal segment. The siphunculi of Jacksonia papillata are brown and scaly, swollen at the base and thinnest in the middle, with the rather small, slightly oblique aperture turned inwards; they are 1.5-1.8 times the length of the cauda. The cauda is short and tongue-shaped with 4-6 hairs. The adult aptera body length is 1.5-1.9 mm.

The alate of Jacksonia papillata has a dark green abdomen with dark marginal, intersegmental and pleural sclerites, cross bars on tergites I, II, VII and VIII, and a central patch on tergites III-VI.

The olive-brown grass aphid lives on grasses, for example meadow grass (Poa pratensis), cocksfoot (Dactylis glomerata), wavy hair grass (Deschampsia flexuosa) and red fescue (Festuca rubra). They usually feed concealed on the colourless basal parts of the stems close to the soil, their colour matching the withered brown leaves. They have also been found on the basal parts of some other plants such as potatoes (Solanum tuberosum) and speedwells (Veronica). They are not, or only exceptionally, visited by ants. Oviparae of this species are unknown, but males of genus Jacksonia have been trapped in Britain. Nevertheless most of the population is thought to overwinter as parthenogenetically reproducing viviparae.

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