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Aphidinae : Macrosiphini : Uroleucon obscuricaudatum
 

 

Uroleucon obscuricaudatum

Dusky-tailed sunflower aphid

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

Identification & Distribution

Adult apterae of Uroleucon obscuricaudatum are red-brown to reddish, with dark antennae & siphunculi, and a dusky cauda (see first picture below). Antennal segment III has 5-14 secondary rhinaria, and bears hairs of length 0.04-0.05 mm. The rostrum reaches or slightly surpasses the third pair of coxae, with the apical rostral segment (RIV+V) 0.75-0.95 times the base of antennal segment VI (cf. Uroleucon parvotuberculatus, which has RIV+V 1.0-1.2 times the base of antennal segment VI). Marginal tubercles are absent (cf. Uroleucon parvotuberculatus, where small pale marginal tubercles are sometimes present on abdominal tergites II-IV). The coxae are pale (cf. Uroleucon compositae which has dark coxae). Antesiphuncular sclerites are present, but fragmented (cf. Uroleucon helianthicola where crescent-shaped antesiphuncular sclerites are present and intact). The siphunculi are reticulated over the apical 0.33-0.4. The cauda is dusky, darkest at its apex, but always paler than the siphunculi (cf. Uroleucon helianthicola, which has a dark cauda; and Uroleucon ambrosiae, which has a pale cauda). The body length of adult Uroleucon obscuricaudatum apterae is 2.7-3.4 mm.

Note: Uroleucon obscuricaudatum belongs to the "ambrosiae complex" of the genus Uroleucon. The most diagnostic feature of this species is the smoky cauda.

First image above copyright Tom Murray, second image above copyright Beatriz Moisset,
both under a Creative Commons Attribution License.

Image above copyright Jeff Ward, under a Creative Commons Attribution License.

Uroleucon obscuricaudatum is monoecious holocyclic on sunflowers (Helianthus spp.) and false sunflowers (Heliopsis spp.). Note that several of the apterae in the picture above are hanging from the branch held only by the rostrum. We have noted this 'behaviour' by stem feeders several times on willow (e.g. Tuberolachnus salignus and Pterocomma pilosum). On one occasion several were dead, but sometimes all are alive. The dusky-tailed sunflower aphid is found in the USA and Canada.

 

Other aphids on the same host

Uroleucon obscuricaudatum has been recorded on 2 species of sunflowers, Helianthus hirsutus and Heliopsis helianthoides.

Acknowledgements

We are grateful to Tom Murray (as Uroleucon helianthicola) of Bugguide, and Beatriz Moisset and Jeff Ward, both of iNaturalist, for making their images of Uroleucon obscuricaudatum available for use under a creative commons licences.

We have used the species accounts of Olive (1965) (as Dactynotus obscuricaudatus) along with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections 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

  • Olive, A.T. (1965). Two new species of Dactynotus from Pennsylvania (Homoptera: Aphididae). Annals of the Entomological Society of America 58(6), 786-791 Full text