Aphis gerardiae

Identification & Distribution

Adult apterae of Aphis gerardiae (see first picture below) are blackish-brown with black siphunculi and cauda. Their antennae are mostly pale, other than antennal segments I & II and the bases and apices of other segments which are dark. The hind tibiae are uniformly dark, or only a little paler in middle (cf. Aphis fabae, which has mostly pale hind tibiae, dark only at the ends). Their siphunculi are about 1.5 times as long as the cauda and equal to, or longer than, twice the length of the hind tarsi (exclusive of claws). The cauda has 7-11 hairs (cf. Aphis fabae, whose cauda has 11-24 hairs). The body length of adult apterae is 1.9-2.9 mm. Immature Aphis gerardiae (see second picture below) are reddish brown.

Note: Aphis gerardiae was covered under the name of Aphis rumicis var gerardiae in Hottes & Frison (1931) and Nielsson (1971).

Image above copyright Ethan Maitra under a Creative Commons Attribution License.

Aphis gerardiae is a specialist on false foxgloves (Agalinis and Aureolaria spp) in the broomrape family (Orobranchaceae). There is no host alternation, and sexual forms are produced in autumn. The false foxglove aphid is widely distributed in eastern USA from New York state southwards to Florida and westwards to Kansas.

Note: we do not know whether or not the species is ant-attended. Nielsson et al. (1971) recorded the ants Camponotus abdominalis floridanus and Solenopsis saevissima richteri attending 'Aphis gerardiae' on fireweed (Erechtites hieraciifolius; syn. Erechtites hieracifolia), but it is now known that the aphid in question was actually Aphis impatientis rather than Aphis gerardiae (Halbert, pers. comm.).

Other aphids on the same host

Aphis gerardiae has been recorded on four species of false foxglove: ridgestem false foxglove (Agalinis oligophylla), slender false foxglove (Agalinis tenuifolia), entireleaf yellow false foxglove (Aureolaria laevigata) and fernleaf false foxglove (Aureolaria pedicularia).

Blackman & Eastop list only 2 species of aphid as feeding on false foxgloves (Agalinis & Aureolaria) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).

Acknowledgements We are especially grateful to Claude Pilon for pictures of Aphis gerardiae. We also thank Susan Halbert (Florida Dept. Agric., Div. Plant Ind.) for passing on her findings regarding the identity of the aphids being attended by ants on Erechtites. 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).

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 Nielsson, R.J. et al. (1971). A preliminary list of ants associated with aphids in Florida. The Florida Entomologist 54(3), 245-248. Full text