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Aphidinae : Macrosiphini : Illinoia thalictri


Illinoia thalictri

Western meadow-rue aphid

On this page: Identification & Distribution Other aphids on the same host

Identification & Distribution

Adult apterae of Illinoia thalictri (see first picture below) are pale sea green to yellowish green, and faintly wax-powdered. Antennal tubercles are widely spaced, each with 3 hairs. Antennae are pale, except for the apices of the segments which are dusky, and segment VI which is dark. The antennae are 1.3-1.5 times the body length, and antennal segment III bears 1-7 secondary rhinaria on the basal 0.17-0.67 portion. The longest hairs on antennal segment III are about 0.5 times the basal diameter of that segment. The rostrum reaches to between the middle and hind coxae, with the apical rostral segment about 0.83 times the second hind tarsal segment. The legs are pale to slightly smoky, with the tips of tibiae slightly darker and tarsi much darker; the first tarsal joints have 5 hairs. The siphunculi are pale to dusky, in some specimens with the swollen area slightly darker. The siphunculi are 0.18-0.33 times the body length, with the apical 0.08-0.13 portion of the siphunculi reticulated; they are swollen over the distal 0.25-0.50 portion up to 1.2-1.7 times the smallest diameter basally. The cauda is conical, about 0.38-0.44 times the siphunculi, with 3 pairs of lateral and 1 dorso-apical hair. Body length of adult Illinoia thalictri apterae is 2.0-2.3 mm.

Note 1: The descriptions and ranges given above are based on a small sample (n=3).
Note 2: Blackman, in Aphids on Worlds, plants suggested that another of Andrew Jensen's images of an aphid on Thalictrum (see second picture below), labelled by Jensen as 'Illinoia corylina?', is also Illinoia thalictri. It is reddish rather than green, but several Illinoia species have both red and green forms.

Images above copyright Andrew Jensen under a creative common licence.

The alate vivipara of Illinoia thalictri has not yet been described. Immatures have a bright green spot at the base of each siphunculus.

Illinoia thalictri is monoecious on the leaves and petioles of Thalictrum sp. The species is holocyclic, with oviparae and brownish-red alate males in September. It is found in western North America.


Other aphids on the same host

Illinoia thalictri has been recorded on only 1 named Thalictrum species (Thalictrum fendleri), but it probably occurs on several others occurring in western North America.

Blackman & Eastop only list 1 species of aphid as feeding on Fendler's meadow-rue (Thalictrum fendleri) worldwide, namely Illinoia thalictri.


We are grateful to Andrew Jensen for making his image(s) of Illinoia thalictri available for use under a creative commons licence.

We have used the species accounts given by MacGillivray (1958) together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections as the source for the (summarized) taxonomic information we have presented. Any errors in information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks


  • MacGillivray, M.E. (1958). A study of the genus Masonaphis Hille Ris Lambers, 1939 (Homoptera, Aphididae). Temminckia 10, 1-131 (p. 36.)