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Varicoloured spirea aphidOn this page: Identification & Distribution Other aphids on the same host
Identification & Distribution
Apterae of Illinoia spiraecola are various hues of red, green and yellow (see first picture below of immature green aptera), often with a darker spinal stripe. The longest hairs on antennal segment III of the adult aptera are 0.30-0.45 times the basal diameter of that segment (cf. Illinoia spiraeae and Illinoia macgillivrayae, which have the longest hairs on antennal segment III 0.20-0.25 times the basal diameter). Antennal segment V is 1.8-2.4 times the length of the cauda (cf. Illinoia spiraeae and Illinoia macgillivrayae which have antennal segment V 1.2-1.8 times the caudal length). The femora and tibiae are light brown and the tarsi black. The first tarsal segments have 3 hairs (cf. Illinoia spiraeae and Illinoia macgillivrayae which have 4-5 hairs on the first tarsal segments). The siphunculi are light brown with a dark tip; they have subapical reticulation with several rows of closed polygonal cells, and are slightly swollen to 1.2 to 1.5 times their basal diameter on the distal third. The body length of adult Illinoia spiraecola apterae is 2.5-3.2 mm.
Note: The other Illinoia species that have been found on Spiraea species (namely Illinoia spiraeae and Illinoia macgillivrayae) only occur in the west of the USA and Canada.
Images above by permission, copyright Claude Pilon, all rights reserved.
Alatae and immature Illinoia spiraecola (see pictures above) are similarly coloured to the adult apterae. Most of our images show the green form, but some of the young nymphs in the picture below are of the yellow form.
Image above by permission, copyright Claude Pilon, all rights reserved.
Illinoia spiraecola feeds on a variety of meadowsweets (Spiraea spp.). There is no host alternation, and it is assumed that sexual forms develop in autumn. Patch (1914) describes finding several colour varieties of the species in Maine on Spiraea x vanhouttei, namely vermillion (scarlet), rose pink, bright green, yellow green, and lemon yellow. It is widely distributed in North America.
Other aphids on the same host
Illinoia spiraeae has been recorded on 4 species of Spiraea (Spiraea alba var latifolia, Spiraea salicifolia, Spiraea thunbergi, Spiraea x vanhouttei). The last of these was given in the earliest record by Patch (1914), but is not included by Blackman & Eastop.