{"id":219,"date":"2015-04-09T02:45:56","date_gmt":"2015-04-09T02:45:56","guid":{"rendered":"https:\/\/aphidtrek.org\/?page_id=219"},"modified":"2025-12-24T17:06:44","modified_gmt":"2025-12-24T17:06:44","slug":"illinoia","status":"publish","type":"page","link":"https:\/\/aphidtrek.org\/?page_id=219","title":{"rendered":"Illinoia"},"content":{"rendered":"\n

Illinoia<\/em> Wilson<\/strong><\/p>\n\n\n\n

This page updated:\u00a0December 2025<\/span>.<\/p>\n\n\n\n

This is one of the groups I study extensively in the field, and puzzle over in the lab.  It is almost entirely North American and is likely very closely related to Macrosiphum<\/em>; in fact the two genera might be better thought of as a mish-mash of similar species haphazardly assigned to genera based on a possibly trivial character, i.e. clavate siphunculi.  But as you’ll see from careful study, some species placed in Macrosiphum<\/em> have clavate siphunculi as well.  So what gives?  Hard to say.  Probably extensive field work and fresh collections for DNA analysis would be required to clarify the genus-level classification.  Meanwhile, there are many cool and easily recognized species of Illinoia <\/em> to enjoy in the field.<\/p>\n\n\n\n

The 2017 collecting season was very productive for me in terms of Illinoia<\/em>.  During winter of 2018 I therefore spent some time sorting many of the unidentified Illinoia<\/em> from many hosts.  One main accomplishment was deciding what to consider as Illinoia thalictri<\/em> MacGillivray.  I knew I had at least two species of the genus from Thalictrum<\/em>, but had not taken the time to decide which should be considered I. thalictri<\/em>.  See below for a photo and an account of this species.  One highlight of my collection work is listed below, and the re-arrangements and species name assignments were reflected in the slide collection database<\/a> when the 2018 version was released. A paper published January 2021 reveals the identity of most Illinoia<\/em> living on Holodiscus<\/em> to be I. gracilicornis<\/em> (MacGillivray). I worked on Illinoia<\/em> classification again in fall of 2020 and decided to broaden what I identify as I. corylina<\/em> to include most specimens living on Corylus, Aguilegia<\/em>, and Thalictrum<\/em> (the latter two genera both in Ranunculaceae). These specimens are obviously different from another species, possibly I. macgillivrayae<\/em>, that also lives on Corylus<\/em> (see below for more information).<\/p>\n\n\n\n

The year 2021 was our first living in western Colorado. It was overall a light year for collecting Illinoia<\/em>, with the exception of samples from various Asteraceae. My first collecting goal here was finding Illinoia masoni<\/em>, which is known to feed on native Helianthus<\/em> (the sunflower genus). To my surprise, finding this species was easy — it lives on native Helianthus<\/em> and apparently other Asteraceae herbs all over our local mountains. I had wondered whether this species would be morphologically distinguishable from others of the genus living on Asteraceae, such as I. goldamaryae, I. grindeliae<\/em>, and I. subviride<\/em>. During December of 2021 I carefully sorted through the specimens I had identified as all of these 4 species. Making a long story short, I was able to make most of the specimens fit into 4 groups, and was able to make a case for species name assignments for each group based on old literature. The collection database released in 2022 will therefore reflect some changes in determinations. Going into this sorting process I understood that 3 of these 4 species had a fairly tight host range. I thought I. grindeliae<\/em> fed on Grindelia<\/em>, I. masoni<\/em> on Helianthus<\/em>, I. subviride<\/em> on Aster\/Erigeron<\/em>, and I. goldamaryae<\/em> was thought to be oligophagous on several Asteraceae genera. Now, it seems clear to me that: I. grindeliae<\/em> feeds on various desert-inhabiting Asteraceae including Grindelia, Heterotheca<\/em>, and a couple others I couldn’t identify; I. masoni<\/em> seems to feed on several genera in wet montane forests, including Helianthus, Helianthella<\/em>, and Erigeron<\/em>; so far I. subviride<\/em> does in fact seem to feed only on Aster\/Erigeron<\/em>. This messy sorting job then made me wonder whether these Asteraceae-feeding species can be distinguished from the I. macgillirayae\/spiraeae<\/em> group? A quick glance indicates that much study will be needed to understand Illinoia<\/em> species delimitation, host ranges, etc.! No characters screamed out to me saying that none of the Asteraceae-feeders are in fact part of that shrub-feeding group. What a taxonomic mess it would be if we learned that most Illinoia<\/em> species are oligophagous or polyphagous! I think I need to set aside some time in retirement to do host transfers among all sorts of plants using local Illinoia<\/em>. <\/p>\n\n\n\n

For a complete report on my Asteraceae-feeding Illinoia<\/em>, please see the essay<\/a> under the “Taxonomy Stories” tab above.<\/p>\n\n\n\n

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Since I work so much with Illinoia<\/em> and especially its relationship and interactions with Macrosiphum<\/em> and Uroleucon<\/em>, I thought I’d make a similar listing effort as I did on the Macrosiphum<\/em> page<\/a>, i.e., discuss all the species in my collection, all those recorded in North America but not in my collection (click here to jump to that list<\/a>), and those species I have that seem to be undescribed (click here to jump to that list<\/a>). According to Aphid Species File<\/a> there are 41 recognized species of Illinoia<\/em>, 40 of them being North American, and 31 of them are represented in my collection.<\/p>\n\n\n\n

Species I’ve identified in my collection (click on the name to jump to that species):<\/h2>\n\n\n\n