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Aphididae : Aphidinae : Macrosiphini : Illinoia
 

 

Genus Illinoia [Macrosiphini]

Illinoia are medium to rather large usually greenish aphids with long siphunculi. The antennal tubercles are well developed, with their inner faces divergent. The median tubercle is frequently also well developed. The siphunculi are weakly to moderately swollen, similar to those of Amphorophora, but with a few rows of rather large polygonal cells occupying the distal 0.06-0.2 of total length. The cauda is shorter than siphunculus, slender and finger shaped.

There are about 45 mostly North American Illinoia species, although some have been introduced to other parts of the world including Europe. Most species retain a sexual stage in the life cycle. There is no host alternation and many species in the two main subgenera are associated with the Heath and Rhododendron family (Ericaceae). Other species feed on taxonomically diverse plants. They are not attended by ants. Some species are important pests of ericaceous plants.

 

Illinoia corylina (Dark-tipped green hazelnut aphid) Western North America

The 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).

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Illinoia crystleae (Pale-streaked honeysuckle aphid) Western North America

Adult apterae of Illinoia crystleae (see first two pictures below) are pale yellowish green, with whitish streaks along the margins of the abdominal tergum and bluish-white wax-dusting on the femora. The femora are pale green, the tibiae pale brown and the tarsi dark. The antennae are 1.3-1.5 times the body length. Antennal segment III has 18-40 small scattered secondary rhinaria on one side of the basal 0.62-0.75 of the segment (cf. Macrosiphum raysmithi on Lonicera ledebourii in California, which only has 0-4 very small rhinaria on segment III). The longest hairs on antennal segment III are 0.42-0.75 times the basal diameter of that segment. The apical rostral segment (RIV+V) is 0.9-1.1 times the second hind tarsal segment (HTII), and bears 13-24 accessory hairs. The legs are mostly pale including the apex of the tibia apart from the tarsi which are dark (cf. Macrosiphum euphorbiae, which has the apices of the tibiae dark like the tarsi). The first tarsal joints have 5 hairs. The siphunculi (see second picture below) are about 0.12-0.28 times the body length, with the apical 0.08-0.12 reticulated. They are swollen on the distal quarter, up to 1.1-1.3 times the smallest diameter basal to it. The cauda is elongate conical with faintly convex sides, at base usually slightly constricted, slightly pointed, about 0.40-0.44 the siphuncular length, with 10-16 hairs. Illinoia crystleae are unusually large, the adult apterae have a body length of 3.7-5.0 mm.

First image above copyright Andrew Jensen under a creative common licence;
second image above copyright Jesse Rorabaugh, no rights reserved.

The alate viviparous female Illinoia crystleae has been described from only one specimen. It is similar to the apterous viviparous female, but antennal segment III bears 42-47 rhinaria scattered along one side over most of its length. The cauda is shorter and more slender.

Illinoia crystleae is monoecious holocyclic on the leaves of bearberry honeysuckle (Lonicera involucrata). It normally feeds on the undersides of the leaves. Oviparae and alate males occur in August-September. The pale-streaked honeysuckle aphid occurs in western North America.

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Illinoia goldmaryae (Bright green daisy aphid) North, Central & South America, Europe, North Africa

Adult apterae of Illinoia goldmaryae (see first picture below) are bright green and elongate oval. The antennal tubercles are well developed and moderately divergent, and the antennae are about 1.1-1.4 times as long as the body. Antennal segment III has 1-7 (usually 2 or 3) secondary rhinaria, extending in a row over about basal third. The longest hairs on segment III are very short at 0.17-0.23 times the basal diameter of that segment (cf. Macrosiphum euphorbiae, which has conspicuous hairs on segment III , the longest 0.5 times the basal diameter or more). The rostrum reaches just past the second pair of coxae (see clarified mount below), with the apical rostral segment 0.81-1.32 times as long as the second hind tarsal segment, and bearing 2 accessory hairs. The abdominal dorsum is smooth with 14-16 hairs on each of tergites I-VI. The legs are light brownish with the apices of the tibiae and the tarsi darker; the first tarsal segments are usually with 3 hairs. The siphunculi (see third picture below) are pale but dusky-tipped, 1.8-2.5 times as long as the cauda, clearly somewhat swollen proximal to the reticulated zone, with 4-5 rows of polygonal reticulations at apex, and a well developed apical flange (cf. Macrosiphum euphorbiae which usually has cylindrical siphunculi). The cauda is elongated, moderately blunt with 6 hairs. The body length of adult Illinoia goldmaryae apterae is 1.8-2.9 mm.

First image above copyright Andrew Jensen, second & third images above copyright Hwalran Choi,
all under creative common licences.

The alate Illinoia goldmaryae (not pictured) is similar to the apterous morph, but has a dark head and thorax, and has dark marginal sclerites and smaller transverse pleural intersegmental sclerites on the abdomen. Antennal segment III bears 17-20 secondary rhinaria over almost the full length of the segment. The last rostral segment is as long as or a little longer than 2nd joint of hind tarsi. The apices of the siphunculi are slightly darker and are reticulated; the swollen area is about 1.1-1.4 times as wide as the widest diameter more basal.The cubital veins in fore wings are slightly bordered.

Illinoia goldmaryae feeds on the the young growth of various genera of Asteraceae, including asters (Aster), horseweeds (Conya), fleabanes (Erigeron) and goldenrods (Solidago). In their native North America, populations are usually monoecious holocyclic, with fundatrices on Solidago in April and males in September, although presumed anholocyclic populations are known where the species has been introduced to other countries. The species is widespread in USA and eastern Canada, Central America and some South American countries. Introduced populations have been reported in England, the Azores and Tunisia.

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Illinoia lambersi (Rhododendron aphid) North & South America, Europe, South-east Asia

Winged and wingless Illinoia lambersi both exist as green, pink and yellow forms (see first picture below of yellow aptera) which can occur in mixed populations (cf. Illinoia azaleae which is always green). The apices of the antennal segments and the tips of the legs are dark. The second segment of the hind tarsus is rather short and less than 1.5 times longer than maximum diameter of the swollen part of the siphunculi (cf. Illinoia azaleae which has the second segment of the hind tarsus more than 1.5 times longer than that diameter). The siphunculi are mostly pale but with darkened apices. They are slightly swollen, strongly attenuated near the tip, and 2.0-2.5 times longer than the cauda. The cauda is mainly pale but dusky towards the tip. The body length of Illinoia lambersi apterae is 2.2-3.3 mm.

The alate of Illinoia lambersi (see second picture above of green alate) has rather indistinct abdominal marginal and intersegmental pleural sclerites. The antennae are only slightly longer than the body and have 21-30 secondary rhinaria placed along the whole segment, not precisely in a row (cf the antennae of Illinoia azaleae which have 7-21 secondary rhinaria in a row).

Colonies of Illinoia lambersi are mainly found on the new shoots and flower buds of rhododendrons and azaleas (Rhododendron), but have also been found on holly (Ilex aquifolium) (cf. Illinoia azaleae which mainly occurs on azaleas). Illinoia lambersi is indigenous to North America where it is widely distributed and sexual forms occur. It is now also well established on rhododendron in South America (Chile), Japan and parts of Europe including Denmark, England and the Netherlands where it overwinters as viviparae.

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Illinoia liriodendri (Tulip-tree aphid) North America, Europe, South-east Asia

Illinoia liriodendri apterae are spindle shaped and pale green, lightly dusted with wax (see first picture below). There are also yellowish and pink-red forms. The antennae are black except at the bases, and are 1.2-1.6 times as long as the body. The legs are pale green except for black apices to the tibiae and tarsi. The siphunculi are black except at the base, and are 2.3-2.9 times as long as the cauda. They are slightly swollen on the distal half, sometimes bent outwards, and with reticulation on the apical one-tenth to one-eighth. The cauda is pale greenish-yellow and is elongate. The body length of an adult Illinoia liriodendri aptera is 1.7-2.5 mm.

The Illinoia liriodendri alate (second picture above) has a brown thorax, a greenish-yellow abdomen and black antennae and legs except for the bases of the femora.

The tulip-tree aphid feeds on undersides of the leaves of tulip tree (Liriodendron tulipifera). Dense populations can build up resulting in large deposits of honeydew on the leaves. Sexual forms occur in autumn. Illinoia liriodendri is native to North America, but in 1998 was found in France. It has since been reported in other European countries and in Japan.

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Illinoia macgillivrayae (Macgillivrays meadowsweet aphid) Western North America

Adult apterae of Illinoia macgillivrayae (not pictured) are pale yellowish-green slender spindle-shaped aphids. Their antennal tubercles are rather well developed, and diverging. The antennae are 1.10-1.25 times the body length; they get gradually darker from the pale base to the blackish apex, with the extreme apices of segments III and IV blackish. Antennal segment III has 1 or 2 rather flat secondary rhinaria. The rostrum reaches to halfway between the second and third pair of coxae, and the apical rostral segment (RIV+V) is 1.05-1.25 times the length of the second segment of the hind tarsi (HTII) (cf. Illinoia spiraeae, which has RIV+V 0.85-1.15 times HTII). The dorsal body hairs are very short and inconspicuous. The legs are long, yellowish, with dark apices to the tibiae. The first tarsal segments of all legs have 5 hairs. The siphunculi are pale, with tips somewhat dark. They have a slightly tapering base, and are then nearly cylindrical, before widening to a maximum in the distal quarter, where they are about 1.3 times as wide as the smallest diameter toward the base; they finally abruptly narrow to the reticulated area, which covers 0.08-0.11 of their length. The siphunculi are 2.35-2.60 times the caudal length (cf. Illinoia spiraeae, which has siphunculi 1.65-2.3 times as long as the cauda). The cauda is pale, with a bluntish apex and 7 hairs. The body length of adult Illinoia macgillivrayae apterae is 2.6-3.2 mm.

Image above copyright Andrew Jensen, under a creative common licence.

Alatae of Illinoia macgillivrayae (see picture above) have a brown head and thorax and a green abdomen. They have 7-9 secondary rhinaria on antennal segment III.

Illinoia macgillivrayae was originally described by Hille Ris Lambers (1966) from specimens found in small colonies on the young leaves of (non-native) Indian hawthorn (Raphiolepis indica). As anticipated, the aphid was subsequently found on other Rosaceae such as the non-native Japanese quince (Chaenomeles japonica), evergreen pear (Pyrus kawakamii), the native ocean spray (Holodiscus discolor) and meadowsweets (Spiraea spp.) In addition it was found on beaked hazelnut (Corylus cornuta). Illinoia macgillivrayae is distributed through western USA and Canada.

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Illinoia maxima (Green-striped thimbleberry aphid) North-western North America

Adult apterae of Illinoia maxima (see first picture below) are whitish green with a slightly darker green dorsal midline, and mainly dusky siphunculi. The antennae are pale, but with the apices of the segments and segment VI darker. The antennal terminal process is 4.5-6.2 times the base of segment VI (cf. Illinoia rubicola, which has the terminal process 5.5-8.2 times the base of that segment). The rostrum reaches to the hind coxae, with the apical segment (RIV+V) about 1.6-1.7 times as long as the second hind tarsal segment (HTII) (cf. Illinoia davidsoni, which has RIV+V 1.9-2.2 times HTII). There are rather prominent, often raspberry-like marginal tubercles on the prothorax and abdominal tergites II-V, those on the prothorax and tergite V being the largest (cf. Illinoia davidsoni, which has marginal tubercles very small or absent; and cf. Illinoia rubicola, which has marginal tubercles present on all of tergites I-VII). ). The legs are pale, with the apices of tibiae and the tarsi darker. The siphunculi are dusky with darker apices and a pale base; they are swollen on the distal third, and the apical part is reticulated (cf. Amphorophora parviflori and other Amphorophora spp., which do not have the siphunculi reticulated). The cauda is pale, with 8-11 hairs. The body length of adult Illinoia maxima apterae is 2.9-3.9 mm long.

Images above copyright Andrew Jensen, under a creative common licence.

Alate Illinoia maxima (see second picture above) have a dark pterostigma and a dark spot at tip of forewing. They resemble the apterae, but with a rather dark head, a partly pigmented pronotum, and the rest of the thorax mostly dark. Antennal segment III has 12-24 secondary rhinaria in an irregular row on the basal 0.67-0.80 part. Wing venation is normal with darkened veins; the forewings have a long, black stigma, and a large dark spot on the tip (cf. Illinoia davidsoni, which has no dark spot on the tip). The siphunculi are light brown to black throughout, reticulated on the distal 10%.

Illinoia maxima is monoecious on leaves of thimbleberry (Rubus parviflorus). The species is holocyclic, but with an 'abbreviated life cycle' (sexual forms are produced in the 3rd or 4th generation in late spring or summer). The biology is described by Frazer & Forbes (1968). The green-striped thimbleberry aphid is found in the moist parts of northwestern North America.

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Illinoia menziesiae (Rusty menziesia aphid) Western North America

Adult apterae of Illinoia menziesiae (see first picture below) are grey-green to salmon pink, with pinkish legs and antennae. The head is smooth, with a distinct median frontal tubercle and moderately prominent, divergent antennal tubercles. The antennae are somewhat shorter than the body length, pale but with the distal half of antennal segment IV, and all of segments V and VI dark. Antennal segment III bears 0-1 secondary rhinaria. The rostrum reaches to the middle coxae, with 10-12 hairs on the apical rostral segment in addition to the usual 3 pairs at the apex. Marginal tubercles are present on prothorax, and occasionally there are also small marginal tubercles on some of abdominal segments I-V. There are 5 hairs on the first tarsal segment (HTI), and both first and second tarsal segments have distinct spinules on the imbrications (cf. Macrosiphum opportunisticum and Macrosiphum parvifolii, which both have 3-4 hairs on HTI and no spinules). The siphunculi are cylindrical, about 1.75 times the length of the cauda, and with 2-3 rows of weak reticulations at the apex (cf. Ericaphis wakibae, which has no subapical polygonal reticulation on its siphunculi). The cauda bears 7 hairs. The body length is 2.0-2.5 mm. Illinoia menziesiae alatae are undescribed.

First image above copyright Andrew Jensen, second image above copyright Walter Siegmund,
both under a creative common licence.

Illinoia menziesia feeds on the undersides of leaves of rusty menziesia (Menziesia ferruginea, see second picture above) causing a discoloring on the top side of the leaves of the host plant, where it causes a yellowing and downward curling of apical portions of leaves. The species is monoecious holocyclic, with oviparae and apterous males in early September-October. It is found in western USA and Canada.

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Illinoia morrisoni (Sequoia aphid) North, Central & South America, Europe

Adult apterae of Illinoia morrisoni (see first picture below) are spindle-shaped and rather dark apple green in colour. The antennal terminal process is 3.6-4.7 times the length of the base of the sixth antennal segment. The first tarsal segments usually have 3 hairs, all subapical, and the apices of the legs are dark. The siphunculi are distinctly swollen and darkened at the tips. The adult apterae are rather small with a body length of 1.5-2.3 mm. Immature Illinoia morrisoni are dusted with a fine wax powder (see second picture below).

Illinoia morrisoni feeds on the terminal leaves and shoots of many species of conifer, mainly in the Taxodiaceae (e.g. Sequoia, Taxodium) and Cupressaceae (e.g. Chamaecyparis, Cupressus, Juniperus, Thuja). Sexual forms have not been described, and it appears to overwinter as parthenogenetic forms. The sequoia aphid is indigenous to western North America, but has now been recorded from Central and South America and several parts of Europe (Britain, France, Italy and Portugal).

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Illinoia richardsi (Pale pearly everlasting aphid) North America

Adult apterae of Illinoia richardsi are spindle-shaped, very pale green with a white wax dusting (cf. Uroleucon russellae, which is bronzy black with dark antennae). The apices of antennal segments, apices of tibiae and the tarsi are darker to blackish. The antennae are about 1.3-1.6 times as long as the body, and have 4-20 secondary rhinaria regularly placed in a row over basal 0.33-0.67 part of segment III. The rostrum reaches to just past the hind coxae. The apical rostral segment (RIV+V) is about 1.5-1.7 times as long as the second hind tarsal segment (HTII), and has 5-9 hairs besides the 3 apical pairs. There are rather large, flat spinal tubercles on the vertex and abdominal tergite VIII, and marginal tubercles on some or all of tergites II-V. The first tarsal joints all have 3 hairs. The siphunculi are about 2.25-2.50 times the caudal length, and have the apical 0.06 distinctly reticulated. They are swollen over the distal part up to 1.4 times the smallest diameter basal to it. The cauda is moderately blunt, not constricted, and with 7 long fine hairs. The body length of adult Illinoia richardsi apterae is 2.6-3.2 mm.

Image above copyright Andrew Jensen, under a creative common licence.

Alatae of Illinoia richardsi (not pictured) are also very pale, but have brownish head, thorax, and antennae; the legs are brownish but the femoral basal halves are pale. The secondary rhinaria on antennal segment III are in a row over nearly its whole length. The wings have rather dark brown wing veins. The siphunculi have a thinner stem than in the apterae, so that the swollen area is about 1.9 times as thick as the smallest diameter basal to it.

Illinoia richardsi has been found on the undersides of the leaves and in the inflorescences of pearly everlasting (Anaphalis margaritacea) and bicolored everlasting (Pseudognaphalium bioletti =Gnaphalium bicolor). It is often found on the flower stems with Uroleucon russellae The species is assumed to be monoecious holocyclic, but the sexual morphs have not been described. Illinoia richardsi is widely distributed in USA and Canada.

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Illinoia rubicola (Spot-winged raspberry aphid) North America

Adult apterae of Illinoia rubicola are pale greenish-yellow, usually with a broad dark green spinal stripe and dark green abdominal margins. The antennal terminal process is 5.5-8.2 times as long as the base of antennal segment VI (cf. Illinoia maxima, which has the terminal process 4.5-6.2 times the base of segment VI). The third antennal segment bears 7-22 secondary rhinaria (cf. Illinoia davidsoni in which antennal segment III bears 20-23 secondary rhinaria). The apical rostral segment (RIV+V) is 1.4-1.85 times as long as the second hind tarsal segment (HTII) (cf. Illinoia davidsoni, which has RIV+V 1.9-2.2 times the length of HTII). There are well developed marginal tubercles present on all of abdominal tergites I-VII, and spinal tubercles usually on tergites VII-VIII (cf. Illinoia maxima, which usually has marginal tubercles only on tergites II-V, and no spinal tubercles). The siphunculi are light brown with darker tips and a sub-apical zone of polygonal reticulation distal to a swollen part (cf. various Macrosiphum and Sitobion species, which have their siphunculi tapering or cylindrical). The body length of adult Illinoia rubicola apterae is 3.1-4.6 mm.

Images above by permission, copyright Claude Pilon, all rights reserved.

Alatae of Illinoia rubicola (see second picture above) have a dark pterostigma and a large black spot at the tip of each forewing (cf. the alate Illinoia davidsoni, which has no black spot at the tip of each forewing). Immatures (see left-most aphid in picture below) have somewhat shorter and less swollen siphunculi, but otherwise resemble the adult apterae.

The spot-winged raspberry aphid can be found on stems of American red raspberry (Rubus strigosus, and on a few other closely-related Rubus spp. Illinoia rubicola is reported as markedly gregarious, and strong colonies are often found on the undersides of the leaves and on the canes near the tip of new growth. It does not host alternate and produces oviparae and alate males in October, overwintering as eggs on raspberry. It is a vector of black raspberry necrosis virus (BRNV), but not of raspberry leaf curl. BRNV causes mild leaf mottle. Illinoia rubicola is widely distributed in the United States and Canada.

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Illinoia spiraecola (Varicoloured spirea aphid) North America

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.

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.

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. In Maine several colour varieties of the species have been found on Spiraea x vanhouttei, namely vermillion (scarlet), rose pink, bright green, yellow green, and lemon yellow. It is widely distributed in North America.

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Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or 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

References

  • Heie, O.E. (1980-1995). The Aphidoidea, Hemiptera, of Fennoscandia and Denmark. (Fauna Entomologica Scandinavica) E.J. Brill, London