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Identification & Distribution

Adult apterae of Aphis neilliae (see first picture below) are dark olive-green or black (see first picture below), or sometimes reddish brown (see second picture below). The antennal tubercles are weakly developed. Their antennal hairs are long and fine, with the longest on antennal segment III being 2.3-3.5 times the basal diameter of that segment. Abdominal tergite VIII has a dark cross-band and bears 6-8 hairs. The siphunculi and cauda are uniformly dark. The siphunculi are tapering, being slightly swollen at the base. The cauda is short, tapering from a broad base to a rounded apex. The body length of adult Aphis neilliae apterae is 1.3-1.8 mm.

Images above by permission, copyright Claude Pilon, all rights reserved.

Immature Aphis neilliae (see pictures below) are dull green or reddish brown, with an indistinct pale spinal stripe.

Images above by permission, copyright Claude Pilon, all rights reserved.

Alatae (see below) are blackish and have 25-37 secondary rhinaria on antennal segment III, 14-23 on segment IV, and 7-15 on segment V.

Image of Aphis neilliae copyright CBG Photography Group under a Creative Commons - Attribution Non-Commercial Share-Alike License.

Aphis neilliae feeds on the leaves and stems of the ninebark shrub (Physocarpus opulifolius) and related Physocarpus species. It does not host alternate, remaining all year on Physocarpus. Sexual forms with apterous males develop in autumn, and the species overwinters in the egg stage. Hottes (1931) observed that in Urbana, Illinois, the species is at times extremely abundant on the undersides of the leaves - and on terminal portions of the new growth of nine-bark used in ornamental plantings. Aphis neilliae is widely distributed throughout North America.

 

Other aphids on the same host

Aphis neilliae has been found on two Physocarpus species (Physocarpus capitatus, Physocarpus ramaleyi) and on one Opulaster (=Physocarpus) species (Physocarpus opulifolius).

Blackman & Eastop list 5 species of aphid as feeding on ninebarks (Physocarpus spp.) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 3 as occurring in Britain (Show British list).

 

Damage and control

Physocarpus opulifolius is cultivated as an ornamental plant, and several cultivars have been bred. Wikipedia notes reports of "armies of aphids attacking some varieties" but that could be any one of the five species of aphid attacking this shrub. Aphids are unlikely to cause any noticeable damage to a shrub, and the best course of action is to leave it to their natural enemies to reduce the aphid numbers.

Acknowledgements

We are especially grateful to Claude Pilon for pictures of Aphis neilliae (for more of her excellent pictures see).

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. Identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Palmer (1952), Hottes & Frison (1931) and Oestlund (1887) supplemented with Blackman & Eastop (1994) and Blackman & Eastop (2006). 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

  • Hottes, F.C. & Frison, T.H. (1931). The Plant Lice, or Aphiidae, of Illinois. Illinois Natural History Survey Bulletin 19(3), 123-447. Full text

  • Oestlund, O.W. (1887). Synopsis of the Aphididae of Minnesota. Minnesota Geological Survey. Bulletin No. 4. Full text

  • Palmer, M.A. (1952). Aphids of the Rocky Mountain Region: including primarily Colorado and Utah, but also bordering area composed of southern Wyoming, southeastern Idaho and northern New Mexico. Thomas Say Foundation, Denver Full text