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Waxy dogwood aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Pseudasiphonaphis corni (see first picture below) are a fairly uniform reddish brown, covered in an extensive light greyish-white woolly wax secretion. The head is rounded in front, with no antennal tubercles. The antennae are light brown, slightly shorter than the body, with a few rather prominent fine hairs about 2-3 times as long as the width of segment III. The antennae have no secondary rhinaria. The terminal process is about 1.4 times the base of antennal segment VI (cf. Anoecia corni on Cornus, whose terminal process is less than 0.5 times the base of segment VI) . The rostrum reaches to the third pair of coxae. The entire dorsum is covered with wax glands. The prothorax and abdominal tergites I-VII bear prominent, toothlike marginal tubercles. The siphunculi are very small, papillate (=with nipple-like extensions), and inconspicuous, though visible in freshly mounted specimens (cf. Aphis gossypii and various Myzus spp. on other Pilea & Scutellaria spp., which have cylindrical or slightly swollen siphunculi). The cauda is brown, long, broad and tapering with about four rather prominent hairs on each side, with the terminal pair of hairs strongly incurved. The body length of adult Pseudasiphonaphis corni apterae is 1.7-2.1 mm.
Images above copyright Charley Eiseman, under a Creative Commons Attribution License.
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
Pseudasiphonaphis corni has been recorded on one dogwood species (Cornus asperifolia).
Pseudasiphonaphis corni has been recorded on 1 clearweed species (Pilea pumila).
Pseudasiphonaphis corni has been recorded on 1 species of clearweed (Scutellaria lateriflora).