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Genus Capitophorus [Macrosiphini]

Pale or almost translucent slender aphids with elongate legs and antennae. Wingless viviparae have long capitate hairs at least on the head and posterior abdominal segments. Winged viviparae only have short hairs and have a dark dorsal abdominal patch.

There are about 30 species worldwide. Some host alternate from oleasters (Elaeagnaceae) to daisies (Asteraceae) and docks (Polygonaceae) whilst others live year round on the secondary host.

 

Capitophorus carduinus (Green thistle aphid)

Wingless viviparae of Capitophorus carduinus are pale greenish white to yellowish green (see pictures below of the two colour forms), almost translucent, often with two indistinct darker green longitudinal stripes. The terminal process of the antenna is 4.6-6.3 times the length of the base of the last antennal segment.

 

Capitophorus carduinus have long capitate hairs on the head and posterior abdominal segments (clearly visible in the micrographs below). Their siphunculi are pale, slender and cylindrical, and are 2.4-3.5 times the length of the cauda. The siphunculi have no distal reticulation and are without dark apices. The body length of wingless viviparae is 1.6-2.2 mm.

Unlike many of the other Capitophorus aphids whose primary host is oleaster (hence sometimetimes known as oleaster aphids) the green thistle aphid does not host alternate. The green thistle aphid lives on the undersides of the lower leaves of thistles (Carduus and Cirsium spp.). Capitophorus carduinus is found in Europe and in various Asian countries.

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Capitophorus elaeagni (Common oleaster aphid)

Apterae in spring populations of Capitophorus elaeagni (see first picture below) on the primary host are pale green. Their abdominal dorsum is reticulate or sculptured, and abdominal tergites 1-4 each have 6-8 hairs, usually one pair each of spinal, pleural and marginal hairs. The siphunculi are cylindrical or tapering. The body length of wingless viviparae on the primary host is 1.9-2.5 mm. Winged viviparae produced on the primary host (see second picture below) have a black head and thorax, black antennae and a blackish dorsal abdominal patch. Wingless viviparae on the secondary host (various Asteraceae) are greenish white to yellowish green with dark tips to the siphunculi. The body length of wingless viviparae on the secondary host is 1.4-2.5 mm.

 

Note: our identification of these aphids as Capitophorus elaeagni was not checked microscopically. Blackman (2010) indicates that the sexual phase of Capitophorus elaeagni that occurs on Elaeagnus in continental Europe has not yet been recorded in Britain, casting doubt on our identification. It could instead be Capitophorus similis which host-alternates between Elaeagnus and Tussilago or Petasites. That said, we observed these forms in the south coast which, if sexual forms of Capitophorus elaeagni occur in Britain, is the most likely place to find them.

The common oleaster aphid host alternates from oleaster (Elaeagnus) or sea buckthorn (Hippophae) to various thistles and daises (Asteraceae). Capitophorus elaeagni is found over most of the temperate and warm temperate parts of the world.

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Capitophorus hippophaes (Polygonum aphid)

Apterae of Capitophorus hippophaes on the secondary host (shown below) are pale greenish to yellowish white, occasionally with longitudinal rows of green spots. The antennae are 0.8-1.2 times the length of the body. Their siphunculi are 2.0-2.4 times the length of the cauda, with the distal two thirds to one half slightly swollen. The cauda has a cylindrical basal part and a triangular, pointed distal part. Capitophorus hippophaes body length is 1.7-2.4 mm. Apterae in spring colonies on the primary host are pale green, slender, with a faint pattern of green spots.

 

Capitophorus hippophaes fundatrices are broadly oval, greenish with reddish spots, and their antennae are dark, 5-segmented and have a short processus terminalis. 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.

Capitophorus hippophaes host alternates from the primary host (various species of Hippophae (sea buckthorn) and Elaeagnus (oleaster)) to a secondary host (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.

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Capitophorus similis (Buckthorn-butterbur aphid)

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. The siphunculi are about 3.5 times the length of the cauda (they are a little shorter on the fundatrix) . On the secondary host, the apterous viviparous female Capitophorus similis is whitish to yellowish white (see upper aphid in first picture below). The antennal terminal process is 6.1-7.5 times the length of the base of that segment. The siphunculi are thin, slightly curved towards their inner sides, with the apices curved outwards, and 3.7-5.0 times as long as the tongue-shaped cauda.

 

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 buckthorn-butterbur aphid host alternates between the primary host, buckthorn (Hippophae) and 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.

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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

  •  Blackman, R.L. & Eastop, V.F. (2012). Aphids on the world's plants: an online identification and information guide. Full text 

 

Identification requests

David Fenwick, 4 August 2013, Aphid on Sea Buckthorn

The Sea Buckthorn the aphid was on is in an amenity setting (i.e. park with ornamentals) in an exposed setting in Bolitho Park, Wherry Town, in a shrubbery parallel with the promenade.

Very mixed coloured juveniles!

Images copyright www.aphotofauna.com  all rights reserved.

   

Bob, Influentialpoints:

  • Its genus is Capitophorus: "Pale or almost translucent slender aphids with elongate legs and antennae. Wingless viviparae have long capitate hairs at least on the head and posterior abdominal segments."

    Which species is a bit more tricky - it does not appear to be Capitophorus hippophaes because the siphunculi are more than 2.7 cauda.

    Could be one of several species...