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Aphididae : Lachninae : Lachnini : Longistigma
 

 

Genus Longistigma

Longistigma aphids

On this page: Longistigma caryae

Longistigma [Lachnini]

Longistigma are very large, bark-feeding aphids. Their antennal tubercles are undeveloped. The antennae are 6-segmented with a short terminal process and few hairs. Secondary rhinaria are present on segment III and, in some specimens, segment V of alatae. Secondary rhinaria are absent in apterae, but commonly present on segment III in apterous-alate intermediates, which are common. The rostrum is clearly 5-segmented, but segment V is fused caplike to the apex of segment IV. The forewing has a long stigma, extending around the tip of the forewing. The radial sector is straight, reaching the margin at the wing apex. The media vein has 3 branches and the branches of the cubitus are narrowly separated basally, and divergent. Abdominal marginal tubercles are absent. The siphunculi are short, almost poriform, each on a large subcircular mammiform base. The cauda is short, almost arc-shaped and the anal plate is entire.

There are two Asian species and one North American.

 

Longistigma caryae (Giant bark aphid)

Adult apterae of Longistigma caryae are pale brownish-grey with 2 longitudinal rows of large black spots (not sclerotised) on each side of the median line of the dorsum, and a transverse series of small black spots along the intersegmental lines. Their dorsum is covered with a variable amount of bluish-white wax powder, and the body, legs and antennae have conspicuously long brown hairs. Antennal segment III is equal in length to segments IV plus V, whilst segment VI is short, about 3 times longer than wide and with the terminal process thumb-shaped. The coxae are dusky, the trochanters and femora, except tips, are reddish-brown, and the tips of the femora, together with tibiae and tarsi, are black except that the middle of the tibia is sometimes reddish-brown. The second hind tarsal segment (HTII) is 1.8-2.3 times the length of the first hind tarsal segment (HTI). The truncate siphuncular cones are black and hairy. The body length of adult Longistigma caryae apterae is 5.1-7.8 mm.

First image above by permission, copyright Claude Pilon, all rights reserved.
Second image above copyright Katja Schulz under a Creative Commons Attribution 2.0 Generic license.

Longistigma caryae do not host alternate, but are highly polyphagous, being found on the bark of numerous tree species in North America including basswood (Tilia spp.), hickories & pecan (Carya spp.), oaks (Quercus spp.) and sycamores (Platanus spp.). In northern USA and Canada sexual forms develop in autumn, producing alate males and apterous oviparae. The population then overwinters in the egg stage. In southern states of the USA populations are anholocyclic.

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Acknowledgements

We have used the keys and species accounts of Wilson (1909) and Foottit & Richards (1993), together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections 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

  • Foottit, R.G. & Richards, W.R. (1993). The Insects and Arachnids of Canada. Part 22. The Genera of the Aphids of Canada (Homoptera: Aphidoidea and Phylloxeroidea). Research Branch, Agriculture Canada. Publication 1885. 766 pp. Full text

  • Wilson, H.F. (1909). Notes on Lachnus caryae Harris, under a new name. The Canadian Entomologist 41 (11), 385-387. Abstract