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Dark spruce stem aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Cinara obscura (see first picture below) are dark brown to black, with pale sections on the tibiae and basal parts of the fore and hind femora. They have paired, lightly sclerotized, broad black patches on the thoracic segments which continue unsclerotized (and hence not visible on the clarified slide mount) down the abdomen as far as the siphunculi. There are also four longitudinal rows of small brown spots dorsally on the abdomen, extending from the thorax to the area between the siphunculi, and two rows laterally, one on each side, around the spiracles. There is usually a partial spinal white wax stripe, and paired dorso-lateral segmental patches of white wax powder (none of which are visible on clarified mounts). The antennae are about 0.4 times the body length. Antennal segment VI is 0.12-0.14 mm, a little shorter than segment V. Secondary rhinaria are distributed 1-2 on segment III, 1-3 on segment IV, and 2 on segment V. The rostrum reaches to the hind coxae. The hind tibiae are less than 1.65 mm long (cf. Cinara hottesi, which has hind tibiae more than 1.65 mm long). Hairs on the hind tibiae are equal to or slightly less than the diameter of the tibia. There is no dark sclerotized crossband on tergite VIII (cf. Cinara pruinosa in Europe & North America, which has a crossband on tergite VIII). The siphunculi are set on large dark siphuncular cones.
Note: Blackman in AWP notes that Cinara pallidipes Hottes is probably a synonym for Cinara obscura.
Images above by permission, copyright Claude Pilon, all rights reserved.
Immature Cinara obscura (see two first instars in first picture above, third and fourth instars in second) are a lighter, more orange-brown than the adults, with the younger instars having the spinal white wax stripe, and paired dorso-lateral segmental wax patches, more in evidence. The wax covering presumably enhances crypsis. The images below show (first) a clarified mount of an apterous vivipara, and second an immature (first instar?) in preservative.
First image above copyright (2010) Her Majesty the Queen in Right of Canada, Agriculture & Agri-Food Canada.
The colour and markings of Cinara obscura alatae (not pictured) are similar to the apterae. Secondary rhinaria are distributed 4-6 on antennal segment III, 1-2 on segment IV and 2 on segment V. Hairs on the antennae are long, about 1.5 times the diameter of segment III. The rostrum extends as far back as the siphunculi.
Image above by permission, copyright Claude Pilon, all rights reserved.
Cinara obscura is monoecious on spruce (Picea), specifically white spruce (Picea glauca) and Engelmann's spruce (Picea engelmannii). Bradley (1953) first described the species after finding them in colonies on the bark of the lower stems of small white spruce growing close together in seed-beds. There are attended by ants, with Formica obscuripes and Formica subnuda being the species so far recorded (Bradley, 1961). Cinara obscura is most likely holocyclic, since fundatrices have been found on Picea glauca in Ontario, but sexuales have not yet been recorded. The species appears to be confined to Canada (Alberta to Newfoundland), although its main host (white spruce) extends into the United States.
Other aphids on the same host
Cinara obscura has been recorded from 2 Picea species worldwide (Picea engelmannii, Picea glauca).