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Lachninae : Lachnini : Lachnus tropicalis
 

 

Lachnus tropicalis

Great chestnut aphid

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

Identification & Distribution

Adult apterae of Lachnus tropicalis (see first picture below) have the head and prothorax brownish-black and the rest of the body shining brownish-grey. Their eyes, antennae and legs are dark brown. The antennae are about half as long as the body with the terminal process 0.45-0.60 times as long as the base of antennal segment VI (cf. Lachnus roboris, which has the terminal process less than 0.45 times the length of the base of segment VI). There are about 9 round small secondary rhinaria on antennal segment III, 5 on segment IV and 1 on segment V. The rostrum is long, nearly reaching halfway down the abdomen. The body is broadly oval with four longitudinal rows of sclerites on the dorsum, which is clothed with numerous fine, short hairs. There is no large tubercle on abdominal tergite IV (cf. Lachnus sorini, which has a large tubercle on tergite IV and a smaller one on tergite V). The legs are long, especially the hind tibiae, with numerous short fine hairs. The siphuncular cones are large and dark, but quite low. The cauda and anal plate are rounded. The body length of adult Lachnus tropicalis apterae is 3.8-5.3 mm.

First image above, by permission Nigel Stott, Natural Japan, all rights reserved.
Second image KKPCW under a creative commons licence.

Alatae of Lachnus tropicalis (see second picture above) have the head light brownish, the thorax black, and the abdomen grey-brown. Their antennae, legs and siphuncular cones are dark. The antennae bear 12-16 secondary rhinaria on antennal segment III, 5-7 on segment IV and 1 on segment V. Alatae have the forewing wholly darkened, except for a clear patch between pterostigma and radial sector, a clear (interrupted) band from base of the media vein to the distal part of Cu1a, and small clear triangles at the distal end of all veins except the cubital veins.

Image above, by permission Nigel Stott, Natural Japan, all rights reserved.

Lachnus tropicalis is monoecious on chestnut (Castanea spp), oak (Quercus spp.) and stone oaks (Lithocarpus spp.). These aphids live rather densely on the upper side of the branches or on the stems, where they are often attended by Lasius niger. Takahashi (1924) comments that in autumn Lachnus tropicalis (=Pterochlorus tropicalis) is often seen grouped on the south side of the stems, where the rays of the sun are falling. It is very active in habit, and when approached, it elevates the posterior pair of legs (see first picture above). When strongly disturbed, it begins to walk away or drops to the ground. The species is holocyclic, apterous oviparae and alate males occur in autumn. After mating, each ovipara deposits 8-14 eggs which, when newly produced, are yellowish brown in colour (see second picture above), which in about a week gradually darken to a deep black. Lachnus tropicalis is found in east and south-east Asia from India to east Siberia, China, Japan, Korea, Vietnam, Laos, Java, and Malaya.

 

Other aphids on the same host

Lachnus tropicalis is recorded on 4 species of chestnut (Castanea crenata, Castanea henryi, Castanea mollissima, Castanea sativa).

Lachnus tropicalis is recorded on 2 species of stone oak (Lithocarpus dealbatus, Lithocarpus elegans)

Lachnus tropicalis is recorded on 15 species of oak (Quercus acuta, Quercus acutussima, Quercus aliena, Quercus dealbata, Quercus dentata, Quercus fabri, Quercus floribunda, Quercus gilva, Quercus glauca, Quercus mongolica, Quercus myrsinifolia, Quercus phillyraeiodes, Quercus semicarpifoilia, Quercus serrata, Quercus variabilis).

Acknowledgements

We are very grateful to Nigel Stott of Natural Japan for permitting us to reproduce his images of Lachnus tropicalis, and to KKPCW for making the pictures of the alate of Lachnus tropicalis available for use.

We have used the keys and species accounts of van der Goot (1916) (as Pterochlorus tropicalis) along 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).

Useful weblinks

References

  • Takahashi, R. (1923/4). Aphididae of Formosa. Part 2. Report of the Department of Agriculture Government Research Institute Formosa 4, p 136. Full text

  • van der Goot, P. (1916). On some undescribed aphides from the collection of the Indian Museum. Records of the Indian Museum 12(1), 1-4 Full text