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Capitophorus carduinus

Green thistle aphid

On this page: Identification & Distribution  Other aphids on the same host 

Identification & Distribution:

Wingless viviparae of Capitophorus carduinus are pale greenish white to yellowish green, 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 (cf. Capitophorus elaeagni  which has siphunculi with dusky to dark apices). The body length of wingless viviparae is 1.6-2.2 mm.

The alate Capitophorus carduinus (see second picture above) have a pale greenish abdomen with a blackish green dorsal patch. Unlike for the aptera, the siphunculi are dark. The ovipara is greenish to yellowish with rather dark swollen hind tibiae. The male is alate and has a greyish green abdomen with three crossbars. The micrographs below show an adult aptera in alcohol, dorsal and ventral view.

The clarified slide mounts below are of adult viviparous female Capitophorus carduinus : wingless, and winged.

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

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

 

Biology & Ecology

Life cycle

Although Capitophorus carduinus is known to produce sexuales, we have found evidence that it may also overwinter parthenogenetically. Viviparous apterae with nymphs have been found in November, for example the individual below was found in November 2018 apparently trapped in spider webbing.

Reproducing viviparae have also been found in mid-February, such as the individual shown below.

The aphids above were both found on the undersides of the lower leaves of thistles growing in suburban areas on paths or roadsides. These plants presumably provide a more favourable environment for the aphids, enabling them to reproduce parthenogenetically through the winter months.

 

Other aphids on same host:

Acknowledgements

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

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).

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