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Appendiseta robiniae

Black locust aphid

On this page: Identification & Distribution  Biology & Ecology 

Identification & Distribution:

All adult viviparae of Appendiseta robiniae are alate. The mature adult alate (see first picture below) has two longitudinal white wax lines on the head and thorax, and four longitudinal rows of powdery white spots on the abdomen. The antennal terminal process is about 0.5 times the length of the base of the sixth antennal segment. The siphunculi are short, truncated cones with a single short hair attached at the base. The cauda is knobbed. The body length of the adult Appendiseta robiniae vivivipara is 1.6-1.9 mm. Immatures (see second picture below) are green with conspicuous long capitate hairs.

The picture below shows an alate vivipara in alcohol.

Appendiseta robiniae is found on the undersides of leaves of black locust (Robinia pseudoacacia) and (much less commonly) on Robinia neomexicana and Sophora japonica. It is native to North America, where it is widespread, and has been introduced to South America, much of Europe and the Middle East.

 

Biology & Ecology:

Life cycle

Appendiseta robiniae lives on the black locust tree (Robinia pseudacia). The tree is native to North America and northern Mexico, but was introduced to Europe in 1601.

The leaves of the black locust tree are pinnate with 9-19 leaflets comprising each leaf (see picture above). Much later the black locust aphid was also introduced.

The immature aphids are pale yellow green (see picture above). They always feed close to the mid-vein of the leaf (see picture below).

Immature aphids appear at first to be without markings, but close examination of the picture below reveals four faint broad bands (two spinal, two marginal) of white wax powdering. Presumably the wax powder in immatures is produced by the same wax glands that produce the four longitudinal rows of powdery white spots on the abdomen of the adult alate.

The "teneral" alate, when first moulted from its fourth instar, has no wax markings (see picture below).

The characteristic wax markings (see picture below) are produced over the next few days.

In September and October sexual forms are produced - the curious elongate apterous ovipara (see picture below) and the alate male.

Borowiak-Sobkowiak & Durak (2012)  carried out field studies on Appendiseta robiniae in Poland in 2008-2009. Their two-year study showed a maximum of 11 aphid generations can develop on Robinia pseudoacacia within the year in Poland. Females of the second and third generations were found to be the most fertile. Their findings indicated that the species had adapted well in Poland, and would probably rapidly increase its population, as happened in Croatia.

Acknowledgements

We especially thank the UK Forestry Commission Bedgebury Pinetum  for their kind assistance, and permission to sample.

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

  •  Borowiak-Sobkowiak, B. & Durak, R. (2012). Biology and ecology of Appendiseta robiniae (Hemiptera: Aphidoidea) - an alien species in Europe. Central European Journal of Biology 7(3), 487-494. 75-83. Full text