Pseudasiphonaphis corni

Identification & Distribution

The alate Pseudasiphonaphis corni has a very prominent median ocellus, and rather large ocular tubercles. The antennae are uniformly brown throughout. Antennal segment III has 7-10 more-or-less circular secondary rhinaria, which are very irregular in size and in a generally straight row over most of the length of the segment. Antennal segment IV has 0 to 2 rhinaria, and segment V has none. The rostrum reaches to the third pair of coxae. The wings are hyaline, the veins dark brown or black, and the stigma dusky. The abdomen is a uniform reddish-brown. The siphunculi are slightly larger and more conspicuous than those on the aptera.

Tissot (1928), who first described this species, describes how a few colonies of this aphid were found in April feeding on the underside of the leaves, and along the tender shoots of a toughleaf dogwood (Cornus asperifolia = Cornus microcarpa). The aphids were confined to two or three plants growing in close proximity to each other. At this time, about half of the mature individuals were winged. For the next few weeks numbers were stable, but by early summer the number decreased rapidly, and by midsummer very few could be found; however they were never entirely absent, which would seem to indicate that they do not host alternate. When the weather became cool in the fall, they began to increase in numbers, and by November there were a few flourishing colonies, all of apterous individuals. Ants were never observed attending the colonies, and at no time were any parasites or predators found. No sexual forms were observed, and it was assumed that, at least in Florida, populations were anholocyclic.

However, in the 1960s, Robinson (1965) reported that Pseudasiphonaphis corni (as Asiphonaphis anogis) had been found further north in the United States on clearweed (Pilea pumila, in the Urticaceae) and mad-dog skullcap (Scutellaria lateriflora, in the Lamiaceae). Also Asiphonaphis anogis was synonomized with Pseudasiphonaphis corni, and Hottes & Frison (1931) had reported alate males of that species being found in October on Pilea. Robinson (1967) therefore concluded that they were host alternating between Cornus, as the primary host, and Pilea/Scutellaria, as the secondary hosts. This is the currently accepted life cycle, albeit there are no records of the return migration to Cornus. Pseudasiphonaphis corni is found in eastern USA and Canada.

Other aphids on the same host

Primary host

Pseudasiphonaphis corni has been recorded on one dogwood species (Cornus asperifolia).

• Blackman & Eastop list 2 species of aphid as feeding on toughleaf dogwood (Cornus asperifolia) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).

Secondary hosts

Pseudasiphonaphis corni has been recorded on 1 clearweed species (Pilea pumila).

• Blackman & Eastop list 1 species of aphid as feeding on Canadian clearweed (Pilea pumila) worldwide, and provide formal identification keys (Show World list). That one species is Pseudasiphonaphis corni. It has not been recorded in Britain (Show British list).

Pseudasiphonaphis corni has been recorded on 1 species of clearweed (Scutellaria lateriflora).

• Blackman & Eastop list 1 species of aphid as feeding on mad-dog skullcap (Scutellaria lateriflora) worldwide, and provide formal identification keys (Show World list). That one species is Pseudasiphonaphis corni. It has not been recorded in Britain (Show British list).

Acknowledgements We are grateful to Charley Eiseman for making his images of Pseudasiphonaphis corni available for use under creative commons licences. We have used the keys and species accounts of Tissot (1929) (as Pergandeidia corni), Hottes & Frison (1931) (as Asiphonaphis anogis), Robinson (1965)(as Pseudasiphonaphis anogis), and Robinson (1967) together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in 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. (p. 225) Full text Robinson, A.G. (1965). A new genus, new species and previously undescribed morphs of aphids (Homoptera : Aphididae). The Canadian Entomologist 97 1009-1015. Robinson, A.G. (1967). A new genus Misturaphis and a new species of Cryptaphis from Manitoba (Homoptera: Aphididae) with a note on Pseudasiphonaphis anogis. The Canadian Entomologist 99(6), 565-569 (p. 569) Tissot, A.N. (1929). A new dogwood aphid from Florida. Florida Entomologist 13(1), 1-4 (p. 2) Full text