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Oceanspray -- cornlily aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Aphis cercocarpi (see first picture below) are shining lead-grey to greenish-black. Their antennae and legs are pale with the tips of the joints dusky and the tarsi, siphunculi, cauda, anal plate and genital plate black. The antennal terminal process is 1.3-2.2 times as long as of the base of antennal segment VI. The rostrum almost reaches the 3rd pair of coxae, and the apical rostral segment (RIV+V) is 1.2-1.7 times the length of the second hind tarsal segment (HTII). The abdominal dorsum is reticulated and has dark spots or patches, but no solid dark shield (cf. Aphis craccivora, which has an extensive solid dark shield on the abdominal dorsum). Abdominal tergites II-IV are usually without marginal tubercles, rarely with just 1 or 2 (cf. an undescribed Aphis sp. on Veratrum in western USA, which consistently has marginal tubercles on tergites II-IV). The tibial hairs are rather long, equalling the diameter of the tibia. The siphunculi are cylindrical, broadening at the base, and longer than the cauda (cf. Aphis schuhi, which has siphunculi shorter than the cauda). The short rather wart-like cauda is bluntly tapering to spatulate with a distinct constriction near the base, and bearing 4-12 hairs (cf. Aphis fabae, which has a cauda bearing 11-25 hairs). The body length of adult Aphis cercocarpi apterae is 1.0-2.3 mm.
Note: Aphis cercocarpi was originally thought to have been collected on Cercocarpus montanus (as Cercocarpus parvifolius), hence the specific name of Aphis cercocarpi (Gillette and Palmer, 1929). However, this is now thought to have been a host misidentification, with the true (primary) host being Holodiscus. Hence Jensen (2021) synonomized Aphis holodisci with Aphis cercocarpi. The aphid is now known to host alternate to Veratrum in summer, leading Jensen to also synonomize the Veratrum-feeding Aphis coweni with Aphis cercocarpi.
Images above copyright Andrew Jensen under a cc by-nc-sa licence.
Aphis cercocarpi alates (see second picture above) have a black head and thorax, and a blackish green abdomen. Their antennae are mostly dark, the tibiae are pale with blackish tips, and the siphunculi and cauda are dusky. There are 15-34 large round secondary rhinaria scattered over the entire length of antennal segment III, 0-13 secondary rhinaria on segment IV, and 0-1 rhinaria on segment V (rhinaria are absent in the aptera).
Aphis cercocarpi was until recently considered to be a monoecious holocyclic species on mountain mahogany (Cercocarpus spp.). Jensen (2021) has now shown experimentally that the species is instead heteroecious holocyclic, migrating from the primary host, ocean spray (Holodiscus spp.) to the secondary host, corn lily (Veratrum spp.). Blackman noted that the presence of apterous males in some locations indicates there is either life-cycle variation or that two cryptic species are involved. Jensen states this is a common species in Oregon and Washington, feeding on Holodiscus discolor. Aphis cercocarpi is often tended by ants. The species is known to occur in western USA and Canada.
Other aphids on the same host
Aphis cercocarpi has been recorded from 2 ocean spray species (Holodiscus discolor, Holodiscus dumosus).