Aphis neogillettei

Identification & Distribution

Aphis neogillettei live in curled leaf pseudogalls (see first picture below) on red-osier dogwood (Cornus sericea = Cornus stolonifera). Their adult apterae are dark olive-green with some red-brown mottling and a more or less dense covering of grey wax powder (see second picture below). The siphunculi, cauda and the apices of the antennae, femora and tibiae are dark (cf. Aphis nigratibialis, which has the tibiae uniformly dark). The antennal terminal process is 1.1-2.1 times the length of the base of segment VI. The hairs on antennal segment III of Aphis neogillettei are long, clearly exceeding the mid-diameter of that segment (cf. Aphis spiraecola, Aphis asclepiadis, Aphis gossypii, Aphis cornifoliae and Aphis impatientis, which all have hairs on that segment short, shorter or equal to the mid-diameter of that segment). Antennal segment III has no secondary rhinaria (cf. Aphis viburniphila, which has 15-23 secondary rhinaria on antennal segments III). The dorsal hairs on abdominal tergites I-VI are usually long, more than 40 µm. Abdominal tergite VIII has 4-6 hairs (cf. Aphis salicariae, which has 6-12 hairs on tergite VIII). The siphunculi are often curved outwards distally, and are about 5 times longer than their width at base. The cauda has 6-11 hairs. The body length of adult apterae is 1.0-1.4 mm. Immature Aphis neogillettei, especially fourth instar alatoid nymphs, have serial white wax markings on the dorsum.

Both images above by permission, copyright Claude Pilon, all rights reserved.

Aphis neogillettei forms dense colonies on red-osier dogwood (Cornus sericea). It is a monophagous (= non-host-alternating) member of the asclepiadis group described by Lagos et al. (2014). This group comprises ten species (Aphis asclepiadis, cornifoliae, decepta, impatientis, neogillettei, nigratibialis, salicariae, saniculae, thaspii, viburniphila) five of which have Cornus as their primary or only host. Sexual forms of Aphis neogillettei develop in autumn. The males are apterous, olive-brown with light yellowish brown appendages. The apterous ovipara is brownish olive-green, but the middle of the dorsum appears yellowish to golden (see second picture above) due to eggs showing through the body wall. The red-osier dogwood aphid overwinters as eggs - which are golden brownish yellow when newly laid, but darken to shining black. Aphis neogillettei is widely distributed in North America.

Biology & Ecology

Life cycle

The life cycle of the red-osier dogwood aphid is described by Griffiths (1980). The fundatrix matures in mid-May and produces apterous fundatrigeniae. At maturity these reproduce on the rapidly developing flower terminals. From this time they produce apterous and alate viviparae, depending on local conditions. By mid-June large, dense, colonies can be found on the flowers. By early July these colonies migrate to the new leaves on growing shoots where they cause extreme leaf-curl. The aphids then slow their reproductive rate, a few alates are produced, and new colonies are initiated. In late August sexuales develop and mating occurs. The overwintering eggs are laid on dogwood throughout September, in the space between the leaf buds and twigs.

Ant attendance

In central Alberta, Canada, several species of ants (Formica fusca, Formica sanguinea subnuda and Tapinoma sessile) have been found tending Aphis neogillettei. Griffiths (1980) examined the effects of ant tending by Formica fusca on Aphis neogillettei. There was some evidence of increased survival of tended colonies. The ants provided protection from predators and parasitoids. Physiological effects of ant tending on the aphids included decreased alate production at low densities, and increased growth rate and fecundity of tended aphids.

Other aphids on the same host

Blackman & Eastop list 16 species of aphid as feeding on Red-osier dogwood (Cornus sericea) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 7 as occurring in Britain (Show British list).

Acknowledgements We are especially grateful to Claude Pilon for pictures of Aphis neogillettei. 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 Palmer (1952) and Lagos-Kutz et al. (2016) 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 Griffiths, C.L. (1980). Effects of ant attendance on aphids. Master of Science thesis, University of Alberta. Full text Lagos, D.M., Voegtlin, D.J., Coeur d'acier, A. and Giordano, R. (2014). Aphis (Hemiptera: Aphididae) species groups found in the Midwestern United States and their contribution to the phylogenetic knowledge of the genus. Insect Science 21 374-391. Full text Lagos-Kutz, D.M. et al. (2016). The status of the members of the Aphis asclepiadis species group (Hemiptera: Aphididae) in the United States of America. Annals of the Entomological Society of America 109(4), 585-594. 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