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Cavariella theobaldi

Willow - parsnip aphid

Identification & Distribution 

Identification & Distribution:

Adult Cavariella theobaldi apterae are green with the tips of the antennae and apices of the legs dark. The antennae are 0.50 times the length of the body and the terminal process is 2.1-3.5 times the base of the last antennal segment. The siphunculi are more than twice as long as the cauda and are cylindrical or tapering from base to the apex; they are not swollen (distinguishes from Cavariella pastinacae which has the siphunculi slightly swollen towards the tip). The supracaudal process is more or less quadrangular and small, about 0.3-0.7 times the length of the cauda. The body length of apterae is 1.8-2.8 mm. The alate has a dark abdominal patch formed by more or less fused cross bands on tergites III-VI. Cavariella theobaldi antennae are dark and the siphunculi are brownish.

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

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

The willow - parsnip aphid host alternates between willows (Salix spp.) and some umbellifers mainly wild parsnip (Pastinaca) and hogweed (Heracleum). Cavariella theobaldi is common over most of Europe and in North America.

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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