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Chaitophorus salijaponicus niger (= Chaitophorus niger)
Dark willow leaf aphidOn this page: Identification & Distribution Biology & Ecology: Life cycle Colour Ant attendance Population dynamics Other aphids on the same host Damage & Control
Identification & Distribution
Adult apterae of Chaitophorus salijaponicus niger (see first picture below) are usually uniformly blackish-brown. The antennae are pale at the base and darker towards the apices. The last two fused apical rostral segments (RIV+V) are 0.8-1.07 times the length of the second hind tarsal segment (HTII) (cf. Chaitophorus salicti, which has RIV+V 1.1 to 1.6 times the length of HTII. Abdominal tergites II-VI 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 femora are mainly dark, but the rest of the legs are mainly pale. The first tarsal segments normally have 5, or occasionally 6, hairs (cf. Chaitophorus truncatus which usually have 6-7 hairs on the first tarsal segments). The siphunculi usually have a broad, clear basal ring separating them from the dorsal shield (best seen on the adult apterae in the second picture below). The cauda is mainly pale and has a distinct constriction dividing it into a triangular basal part and a globular apical knob. Immatures (see second picture below) are a characteristic wine red with a yellowish suffusion around the siphunculi.
Alate Chaitophorus salijaponicus niger (see third picture above) are dark, with broad dorsal abdominal cross-bands. The pale legs and antennae are useful distinguishing features.
The micrographs below show an adult apterous Chaitophorus salijaponicus niger, dorsal and ventral views, in isopropyl alcohol.
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
The fundatrices hatch from overwintering eggs on willow stems in spring.
Unlike the related species Chaitophorus salicti, Chaitophorus salijaponicus niger tends not to 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).
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.
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.
Other aphids on same host
Chaitophorus salijaponicus niger has been recorded on 35 Salix species.
Blackman & Eastop list over 120 species of aphids as feeding on willows worldwide.
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.