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Waxy spruce aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Adult apterae of Mindarus obliquus are yellowish green, but appear whitish due to their covering of wax wool (see pictures below). The eyes of Mindarus obliquus usually have several facets in addition to the triommatidia (cf. Mindarus abietinus, which has eyes consisting only of triommatidia). The apical rostral segment (RIV+V) is about 0.5 times as long as the base of antennal segment VI. Marginal wax pore plates are usually present on abdominal tergites I-VII or II-VII, but spinal and pleural wax pore plates are reduced or absent except on their most posterior tergites. Small siphuncular pores are present in the apterous morph and the embryo (but not in the fundatrix), as can be seen in the preserved specimen further down the page (cf. Mindarus abietinus, which has no siphuncular pores in either the aptera or embryo). The body length of the Mindarus obliquus aptera is 1.2-1.9 mm.
First two images above by permission, copyright Claude Pilon, all rights reserved.
The winged viviparae of Mindarus obliquus (see second picture below) have dark dorsal abdominal cross-bands. They have 7-13 secondary rhinaria on antennal segment III, and 1-4 rhinaria located near the distal end of segment IV (cf. Mindarus abietinus, which has 14-27 rhinaria on segment III and usually only one rhinarium on segment IV). Antennal segment III is 0.23-0.32 mm long, and usually less than 0.31 mm (cf. Mindarus abietinus, where that segment is 0.31-0.49 mm long, but usually more than 0.31 mm). Alatae usually have the media of their forewing once-branched. The body length of alate Mindarus obliquus is 1.0-1.6 mm (cf. the alate of Mindarus abietinus, which is larger, having a body length of 1.5-2.7 mm).
Images above copyright CBG Photography Group under a Creative Commons License.
Mindarus obliquus is known to feed on several species of spruce especially Engelmann spruce (Picea engelmannii), white spruce (Picea glauca), and Sitka spruce (Picea sitchensis), but not on any firs (Abies spp.) which supposedly only host Mindarus abietinus. However, the molecular methods used to identify these aphids also indicated Mindarus obliquus for several samples from firs in Quebec, Canada (these specimens are not pictured above) - which suggests we have much more to learn about the host preferences of Mindarus species. Mindarus obliquus is thought to have originated in the Nearctic region given it does not feed on Palaearctic spruces such as Norway spruce (Picea abies). It feeds between the needles on new shoots in spring, but it does not deform the needles. The life cycle is holocyclic with small apterous sexuales developing in June-September. Mindarus obliquus is found in Canada and Alaska (and possibly some other northern U.S. states), plus Europe, east to Turkey (and possibly China).
Other aphids on the same host
Mindarus obliquus has been recorded on 5 species of spruce (Picea engelmannii, Picea glauca, Picea mariana, Picea omorika, Picea sitchensis).