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Identification & Distribution

Chaitophorus capreae apterae are white to yellowish-white to bluish-green (see pictures below) with no distinct dark dorsal abdominal markings (cf. Chaitophorus salicti, which has more-or-less extensive dark markings on the dorsum). Antennal segment III has only 0-4 hairs, the longest of which are 5-20 µm long. The body is not markedly narrow: the body length 1.8-2.1 times the maximum body width (cf. Chaitophorus horii beuthani, which is more elongate with a body length 2.1-2.5 times the maximum body width, and occurs on narrow-leaved Salix species). The dorsum and appendages bear numerous furcate (=forked) hairs (see second picture below). The cauda has a distinctly knobbed apex. The body length of Chaitophorus capreae is 0.8-1.9 mm.

Chaitophorus capreae alatae are yellowish white with no solid dark segmental bands on the abdominal tergites. Instead there is a much broken pattern on the middle tergites not forming anything like a mid-dorsal rectangular patch.

The pale sallow leaf aphid lives mostly on sallows (broad-leaved Salix spp.) especially great sallow (Salix caprea) and grey sallow (Salix cinerea). Aphids are usually scattered on the undersides of leaves although dense colonies can occasionally develop. They are not attended by ants (cf. Chaitophorus salicti and Chaitophorus ramicola, which are usually attended by ants). Brown oviparae and deep yellow apterous males (see pictures below) occur in October-November. Chaitophorus capreae is widespread in Europe, and eastward to Central Asia.

 

Biology & Ecology

Habitat

Typically Chaitophorus capreae is found scattered on the undersides of sallow leaves.

We have found Chaitophorus capreae in numerous locations in southern Britain from late April to November, usually in low numbers, as shown in the pictures below.

We have, however, found one very large colony on sallow planted for hedging in a car park. It is not unusual to find aphids, which typically occur in small numbers, occurring in abnormally large numbers when the host plant is cultivated - the same occurs with Myzocallis coryli when hazel is used for hedging. Note that the picture below shows a mixed-species colony - the larger green aphid in the bottom right quadrat is not a Chaitophorus capreae but a Cavariella species.

Life cycle

Chaitophorus capreae overwinters as eggs laid on the stems of Salix. These hatch in April to give the fundatrices. Numbers then increase although very dense colonies seldom occur. The species does not host alternate, but remains all year on broad-leaved Salix species. Very distinctive sexual forms then develop in the autumn.

The males are small and deep yellow with dark antennae (see picture below).

Teneral (=recently ecdysed) oviparae are pale green with darker green patches (see first picture below).

Mating then occurs between the oviparae and the males.

The ovipara are quite long-lived and over time they darken from green to brown (see picture below).

Ant attendance

Most of the literature (e.g. Shingleton (2005)) indicates that Chaitophorus capreae is not attended by ants, and we have never found ants in attendance even at the unusually large colony above. We note that Litschauer (2008) has reported that the species has a mutualistic relationship with ants in Austria, but this may be a result of misidentification of the aphid.

Natural enemies

In July the colony above was heavily attacked by a parasitoid. The first picture below shows two parasitized mummies together with some live nymphs.

The second picture above shows the adult braconid parasitoid that emerged from one of the mummies. The wing venation (namely the lack of forewing vein M+m-cu) and the host aphid suggest that the parasitoid is Adialytus salicaphis. This species has been recorded attacking Chaitophorus on broad-leaved sallows in south-eastern Europe by Tomanovic et al. (2006). Adialytus salicaphis was recorded for the first time in Britain by Baker & Broad (2009). They suggest that it may well be common, but has been overlooked because it does not attack pest aphid species.

The only predator we have encountered attacking Chaitophorus capreae is an immature anthocorid shown in the picture above.

 

Other aphids on same host

Chaitophorus capreae have been recorded from 23 Salix species.

 

Damage and control

Sallow has few uses other than for ornamental purposes, and is considered a weed in some countries. Hence there is seldom any need for control of the aphids. Unlike some other parasitoid species (for example Lysiphlebus fabarum), the parasitoid we have found (Adialytus salicaphis) does not seem to attack crop pest aphids, so Chaitophorus capreae populations would not provide a useful reservoir for parasitoids.

Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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

  • Baker, E.A. & Broad, G.R. (2009). Five aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) new to Britain. British Journal of Entomology & Natural History 22, 255-263. Abstract

  • Litschauer, C. (2008). Trophobiotic associations between ants and honeydew producers in Eastern Austria. M.Sc. thesis. Full text

  • Shingleton, A.W. et al. (2005). The origin of mutualism: A morphological trait promoting the evolution of ant-aphid mutualisms. Evolution 59(4), 921-926. Full text

  • Stroyan, H.L.G. (1977). Homoptera: Aphidoidea (Part) - Chaitophoridae and Callaphidae. Handbooks for the identification of British insects. 2 (4a) Royal Entomological Society of London. Full text

  • Tomanovic, Z. et al. (2006). Aphids and parasitoids on willows and poplars in southeastern Europe (Homoptera: Aphidoidea; Hymenoptera: Braconidae, Aphidiinae). Journal of Plant Diseases and Protection 113(4), 174-180. Full text