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Manitoba dogwood aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Macrosiphum manitobense (see pictures below of first and second generation apterae on Cornus) are green or pinkish green. The siphunculi are mostly dusky, but dark on the distal 0.10-0.15 and pale on the basal 0.20-0.30. Antennae have the tips of segments III-IV, and all of segments V & VI, dusky to dark. The antennal tubercles are diverging and not strongly produced, and the median frontal tubercle is prominent. The base of antennal segment VI is much shorter than segments I + II together (cf. Macrosiphum cornifoliae on Cornus in the Far East, which has the base of segment VI about the same length as segments I + II together). There are 4-6 secondary rhinaria on the basal 0.4 of antennal segment III. Hairs on antennal segment III are less than half as wide as the segment at mid-length. The rostrum reaches to the third pair of coxae. Marginal tubercles are usually present on the abdominal segments, and there are usually a pair of spinal tubercles on each of abdominal segments VII and VIII. Dorsal body hairs are short, usually with globose apices. The abdomen is not sclerotic. There are small dark spots which show a cell-like pattern along the sides of the abdomen. The siphunculi are imbricated, cylindrical, tapering, and with a flange. The siphunculae are slightly attenated at the reticulated area, which covers the apical 0.15. The cauda is denticulate (=finely toothed) with 7 hairs, and rather short, usually about 0.1 of body length (cf. Macrosiphum euphorbiae & Macrosiphum hamiltoni, both in North America, where the cauda is over 0.14 times the body length). The body length of adult Macrosiphum manitobense apterae is 2.5-2.8 mm.
Alatae of Macrosiphum manitobense (not pictured here) are colored as the apterae, but have the head and thorax dusky, and the antennae dusky or dark. There are 24-43 secondary rhinaria on antennal segment III. The abdomen is pale, except for light brown marginal sclerites, and rows of cell-like markings mostly along the sides of the abdomen. Most dorsal hairs are globose at the apices. The siphunculi are pale at the base, becoming gradually darker towards the apex.
Macrosiphum manitobense feeds on red osier dogwood, Cornus sericea (=C. stolonifera), and on an unidentified Cornus species. It is thought to be holocyclic, but the presumed secondary host is unknown. So far it has been found in Manitoba, Canada, and in western Oregon and Washington, USA.
Other aphids on the same host
Macrosiphum manitobense has been found on 2 dogwood species (Cornus sericea = Cornus stolonifera, Cornus sp.).
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).
Macrosiphum manitobense is thought to have a secondary host, because it disappears from Cornus in July and August. However, the identity of that presumed secondary host is as yet unknown. It has been suggested that it is Potentilla on the supposition that Macrosiphum manitobense is the primary host form of Macrosiphum potentillae, a species occurring in the same area first described by Oestlund (1887) (as Nectarophora potentillae).