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Polygonum aphid, Bistort aphidOn this page: Identification & Distribution Biology & Ecology Life cycle Other aphids on the same host
Identification & Distribution:
Apterae of Capitophorus hippophaes on the primary host (sea buckthorn) in spring are pale green or sometimes reddish, with a faint pattern of green spots. On the secondary host (redshank) the aphids are pale greenish to yellowish white (see first picture below), occasionally with longitudinal rows of green spots. The antennae are 0.8-1.2 times the length of the body. The siphunculi of Capitophorus hippophaes are 2.0-2.4 times the length of the cauda, with the distal two thirds to one half slightly swollen. (cf. Capitophorus elaeagni & Capitophorus similis both feeding on sea buckthorn which do not have swollen siphunculi) . The cauda has a cylindrical basal part and a triangular, pointed distal part. The body length of adult apterae is 1.7-2.4 mm.
Capitophorus hippophaes alates are greyish-green with a black head and thorax, dark antennae, legs and siphunculi and a large quadrate dark green patch on the dorsal abdomen. Fundatrices are broadly oval, greenish with reddish spots, and their antennae are dark, 5-segmented and have a short processus terminalis. Micrographs below show adult apterae in alcohol (first) from primary host, dorsal view and (second) from secondary host, ventral view.
Capitophorus hippophaes host alternates: The primary hosts are various species of Hippophae (sea buckthorn) and Elaeagnus (oleaster). The secondary hosts are various Polygonum and Persicaria species. Aphids live on the undersides of the leaves. Capitophorus hippophaes occurs in Europe, north Africa, south-west Asia, and has been introduced into North America. A subspecies, Capitophorus hippophaes javanicus occurs on Polygonaceae in south-east Asia, Australia, New Zealand, South America, and also in California, USA.
Biology & Ecology
The overwintering eggs laid the previous autumn on sea buckthorn hatch in spring to give the fundatrices. Like the regular viviparae, the fundatrix has swollen siphunculi, but is distinguished by its characteristic reddish colour (see picture below).
The offspring of the fundatrix are also reddish, at least in the nymphal stages (see picture below).
It appears that either some aphids remain on the primary host all summer, or else return much earlier, as Dave Fenwick found a colony with the characteristic swollen siphunculi on sea buckthorn in Cornwall in August (see picture below), when they should have moved to their secondary host.
Image above copyright Dave Fenwickall rights reserved.
However, many do migrate to their summer hosts, one of which is redshank (Persicaria maculosa) (see picture below).
The aphids on the secondary host are usually very pale and unmarked (see second picture above), but may also have greenish spots. The characteristic swollen siphunculi are clearly visible both on the apterae and alatae.
They normally return to the primary host in September/October . The first picture below shows a returning alate gynopara on sea buckthorn in late September. The second shows a returning alate male. Note especially the darkened siphunculi of the alate of this species.
By late October the offspring of the returning alates have developed to oviparae (not pictured), which, after mating, lay their eggs on the sea bluckthorn twigs.
Predators do not seem to be much in evidence on the primary host, but an exception is spiders (see picture below) which abound on the sea buckthorn leaves, eating the alates as they arrive.
Other aphids on same host:
Blackman & Eastop list 10 species of aphid as feeding on oleaster (Elaeagnus species) and/or sea buckthorns (Hippophae species) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 4 as occurring in Britain (Show British list).