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Illinoia corylinaDark-tipped green hazelnut aphidOn this page: Identification & Distribution Other aphids on the same hostIdentification & DistributionThe fundatrix of Illinoia corylina (see first picture below) is green with the siphunculi dark on their apical 75%. Subsequent adult apterous viviparae (see second picture below) are green with slightly swollen siphunculi, having only the tips dark, and the remainder dusky or pale. The antennal tubercles are well developed. The antennae are slightly longer than the body, progressively darker from the pale brown base to the dark brown apex, and bearing 2-4 flattish secondary rhinaria on antennal segment III. The rostrum just reaches the hind coxae. The apical rostral segment (RIV+V) is 1.4-1.5 times the length of the second hind tarsal segment (HT II), and bears 14-16 accessory hairs (cf. Illinoia macgillivrayae, which has RIV+V 1.95-1.25 times HTII and bears 6-9 accessory hairs). The dorsal cuticle is smooth, but not sclerotic. Marginal tubercles are small & low. The distal 12% of the siphunculi is dark brown. The siphunculi are slightly, but distinctly, swollen proximal to the reticulated subapical zone (cf. Macrosiphum pseudocoryli, which has long, but tapering siphunculi). The cauda is pale, elongated, bluntly triangular with no constriction, and bears 7 hairs. The anal plate is entire. The body length of adult Illinoia corylina apterae is 2.3-2.5 mm.
Images above copyright Andrew Jensen, under a creative common licence. Illinoia corylina alatae (not pictured) are apple green with the head and thoracic lobes dark green. The antennae are longer than the body, and bear 23-28 secondary rhinaria on antennal segment III. The wing veins are dark brown. The siphunculi are nearly one-third the length of the body, with the apical two-thirds dusky, and slightly swollen. The cauda is pale green, tapering and with the apex upturned. Illinoia corylina has generally been assumed to be monoecious holocyclic on Western beaked hazel (Corylus rostrata = Corylus cornuta var. californica). However earlier workers, and more recently Jensen, have found what appears to be the same species on Aquilegia and Thalictrum (both in the Ranunculaceae). A picture of a possible Illinoia corylina found feeding on Thalictrum is shown in aphidtrek. Illinoia corylina has also been found by Davidson (see Swain, 1919) on an unrelated species, Ninebark (Physocarpus capitatus) in the Rosaceae. It is found in the western USA (California, Oregon, and Washington). Other aphids on the same hostIllinoia corylina has been recorded on 1 Corylus species (Corylus cornuta).
Illinoia corylina has been recorded on 1 Aquilegia species (Aquilegia formosa).
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