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Identification & Distribution:

On the primary host both the fundatrix and viviparous females of Capitophorus similis are pale greenish, frequently a little reddish, and with longitudinal rows of green spots. On the secondary host, the apterous viviparous female Capitophorus similis is whitish to yellowish white (see first picture below). For apterae on the primary host, the antennal terminal process is 5.0-6.0 times the length of the base of that segment; on the secondary host it is 6.1-7.5 times the length of the base of that segment. Abdominal tergites I-IV each have 4 spinal, 4 pleural and 6 marginal hairs (cf. Capitophorus elaeagni which usually has 2 spinal, pleural and marginal hairs on each of tergites I- IV). The apterous viviparae have siphunculi that are thin and not swollen (cf. Capitophorus hippophaes which have the distal two thirds to one half of their siphunculi slightly swollen). For apterae on the primary host, the siphunculi are about 3.5 times the length of the tongue-shaped cauda. For apterae on the secondary host, the siphunculi are thin, cylindrical, slightly curved towards their inner sides, with the apices curved outwards, and 3.7-5.0 times as long as the cauda. The body length of wingless viviparae on the secondary host is 1.5-2.6 mm.

The alate female Capitophorus similis (see second picture above) has a greenish-white abdomen, with rather large, dark marginal sclerite and postsiphuncular sclerites, a black quadrangular dorsal patch on tergites 3-6, and small sclerites on the posterior tergites. The micrographs below show a Capitophorus similis aptera from the secondary host in alcohol, dorsal and ventral views.

The clarified slide mounts below are of adult viviparous female Capitophorus similis : wingless from primary host, and secondary host, and winged spring migrant.

Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.

The buckthorn-butterbur aphid host alternates from the primary host, buckthorn (Hippophae) and oleaster (Elaeagnus) to the secondary host, coltsfoot (Tussilago) or butterbur (Petasites). Males and winged females are produced in autumn. Capitophorus similis is distributed throughout Europe into the eastern Himalayas in Asia.

 

Biology & Ecology

Life cycle

One of the primary hosts of Capitophorus similis is sea buckthorn (Hippophae rhamnoides) - a thorny shrub which grows in coastal areas (see images below). The other primary host is oleaster (Elaeagnus) (not shown).

 

Two species of Capitophorus are known to overwinter on sea buckthorn and oleaster in Britain, Capitophorus similis and Capitophorus hippophaes, and two others, Capitophorus elaeagni, and Capitophorus pakansus may do so. The picture below shows immature Capitophorus on oleaster (Elaeagnus angustifolia). Since the siphunculi are not swollen, they are most likely to be Capitophorus similis.

The picture below shows a mature Capitophorus similis on oleaster.

The secondary hosts of Capitophorus similis are the undersides of the leaves of butterbur (Petasites) (see first picture below) and coltsfoot (Tussilago) (see second picture below).

 

We have found large colonies of Capitophorus similis on butterbur leaves, with aphids fairly widely spaced out over the underside of leaves.

 

The capitate hairs characteristic of aphids of this genus are clearly visible in the picture of the apterous adult below.

Gynoparae (alate females which produce oviparae) and (usually somewhat later) alate males migrate back to the primary host in September to October. These stages are shown below.

The oviparae are yellowish green mottled with darker green and orange-yellow (see picture below).

The ovipara lays her overwintering eggs on the oleaster.

Natural enemies

Several likely predators were present on the butterbur leaves including midge larvae (see first picture below) and anthocorid bugs (see second picture below).

 

Note, however, that the anthocorid bugs may not have been predating the aphids, instead either feeding on plant liquids or on the aphid honeydew.

 

Other aphids on same host:

Primary hosts

Capitophorus similis has been recorded from 3 Elaeagnus species (Elaeagnus angustifolia, Elaeagnus commutata, Elaeagnus umbellata) and from 2 Hippophae species (Hippophae rhamnoides =Elaeagnus rhamnoides, Hippophae salicifolia).

Blackman & Eastop list 10 species of aphid as feeding on sea buckthorns (Hippophae species) and/or oleaster (Elaeagnus species) worldwide, and provide formal identification keys.

Of those aphid species, Baker (2015) lists 4 as occurring in Britain: Capitophorus hippophaes, Capitophorus elaeagni, Capitophorus similis and Capitophorus pakansus.

Secondary hosts

Acknowledgements

We especially thank Rye Harbour Nature Reserve for their kind assistance, and permission to sample. Also, Alan Outen Bedfordshire Invertebrate Group, for identifying the butterbur leaves shown above.

Our particular thanks to Roger Blackman for images of his clarified slide mounts.

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).

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