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Chaitophorus salijaponicus niger (= Chaitophorus niger)

Dark willow leaf aphid

On this page: Identification & Distribution  Biology & Ecology  Damage & Control 

Identification & Distribution:

Adult apterae of Chaitophorus salijaponicus niger are usually blackish-brown with a pale ring around the bases of the siphunculi (see first picture below). Abdominal tergites 1-6 or 2-6 are fused into a solid carapace. The dorsal cuticle is sculptured with wavy lines of small bead-like or denticular spinules that tend to form reticulations in the mid-thoracic and anterior abdominal region. The antennae, legs and cauda are mainly pale. Immatures are either wine red with a yellowish suffusion around the siphunculi or blackish.

Alate Chaitophorus salijaponicus niger (see second picture above) are dark, with broad dorsal abdominal cross-bands. The pale legs and antennae are useful distinguishing features.

Dark willow leaf aphids live separately or in small colonies on leaves of willow (narrow-leaved Salix spp.), only rarely visited by ants. Oviparae and males occur in September-November. Whether males are apterous or alate seems to depend on geographical location. Chaitophorus salijaponicus niger are found in Europe and across Asia to Siberia, but are replaced by a different subspecies in China and Japan.

 

Biology & Ecology:

Life cycle

The fundatrices hatch from overwintering eggs on willow stems in spring.

Unlike the related species Chaitophorus salicti,  Chaitophorus salijaponicus niger does not concentrate along the main veins. Instead they form small groups over the leaf surface. The colony below has all stages present, from the wine red young nymphs, to the somewhat darker fourth instars, to the black apterae.

Sexual forms develop in October (see picture below of the ovipara).

 

Colour

All the colonies we have found on narrow-leaved willows (such as Salix alba) have had wine-red immatures as shown in the picture below.

But the single colony of this species on sallow (Salix caprea) had dark brown immatures (see picture below).

We initially thought that perhaps we had misidentified the sallow-feeding aphid, and that it was instead the dark form of Chaitophorus salicti, a not uncommon species on sallow. But the pattern of dispersion of the aphid (not concentrated along the main veins) convinced us that they are indeed Chaitophorus salijaponicus niger.

 

Ant attendance

Occasionally ants will attend Chaitophorus salijaponicus niger for the honeydew (see picture below).

But this species is rarely ant-attended, possibly because it has rather short mouthparts since it feeds on the leaves rather than the stem.

The hypothesis put forward by Shingleton et al. (2005)  that it is not worthwhile for aphids with short mouthparts (and hence a short 'escape time' from predators) to invest the necessary energy in attracting ants to their honeydew.

 

Population dynamics

Molnár (2003)  looked at the population dynamics of willow aphids including Chaitophorus salijaponicus. Numbers showed two peaks, with the spring peak higher than the summer one. There was no significant  relationship between numbers and rainfall.

We have not yet found parasitoids of this species, but Rakhshani et al. (2007)  has recorded Adialytus salicaphis parasitizing Chaitophorus salijaponicus in Iran.

 

Damage and control

Willows (narrow-leaved Salix species) have many commercial uses especially for biofuel, environmental purposes and (for a few items) the wood. Its use for biofuel has prompted renewed interest in the pest complex attacking willows. However, Chaitophorus salijaponicus niger is seldom common enough to be worth any specific control measures.

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 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

  • Molnár, N. (2003). Population dynamics features of willow-feeding aphids. Acta Phytopathologica et Entomologica Hungarica 38 (1-2), 125-135. Full text 

  • Rakhshani, E. et al. (2007). Parasitoid (Hymenoptera, Braconidae, Aphidiinae) associations on willows and poplars in Iran. Acta Zoologica Academiae Scientiarum Hungaricae 53(3), 281-292. 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