Illinoia

Members of Illinoia can be distinguished from other Macrosiphini aphids by a combination of morphological features including the presence of siphunculi (cornicles) on the posterior abdomen, typical of Aphididae. Specific identification to species requires examination of host association and detailed morphological characters; for example, I. liriodendri is reliably identified by its exclusive association with Liriodendron tulipifera in combination with genetic confirmation. The genus belongs to the tribe Macrosiphini, which is characterized by long antennae and siphunculi.

Species within Illinoia occupy habitats defined by their host plants. I. liriodendri occurs on ornamental tulip trees in urban forests and landscaped settings. I. pepperi is associated with blueberry cultivation. I. lambersi occurs on rhododendron. The genus is found in temperate regions, with individual species distributions tied to the cultivation or natural occurrence of their respective host plants.

The genus has a broad distribution corresponding to host plant availability. I. liriodendri is native to eastern North America and has been introduced to Europe (Spain, France, Germany, Italy, Slovenia, UK, Croatia), Japan, and northern California. I. pepperi occurs in Michigan and other blueberry-growing regions of North America. Distribution records for the genus include Denmark, Norway, and Sweden.

I. liriodendri shows highest infestation levels in May and June in Spain, with a monoecic-holocyclic annual cycle. I. pepperi exhibits seasonal phenology tied to blueberry cultivation in Michigan. Seasonality varies by species and latitude.

Phloem-feeding on specific host plants. I. liriodendri feeds on Liriodendron tulipifera (tuliptree/tulip poplar) and has been recorded on Magnolia grandiflora (southern magnolia). I. pepperi feeds on blueberry. I. lambersi feeds on rhododendron. I. pisi feeds on pea.

• Liriodendron tulipifera - primary hostTuliptree/tulip poplar; host of I. liriodendri
• Magnolia grandiflora - secondary hostSouthern magnolia; recorded host of I. liriodendri
• Vaccinium - primary hostBlueberry; host of I. pepperi
• Rhododendron - primary hostHost of I. lambersi
• Pisum sativum - primary hostPea; host of I. pisi

I. liriodendri has a monoecic-holocyclic annual life cycle, completing its entire life cycle on a single host species with sexual and asexual generations. This life cycle type has been explicitly demonstrated in European populations. Life cycle details for other species in the genus vary and are not uniformly documented.

I. liriodendri produces honeydew, with a strong positive relationship between infestation severity and honeydew dripping observed. The species commonly reaches high densities on urban trees. I. lambersi has been documented as prey for lacewing predators under experimental temperature regimes.

Species in Illinoia serve as prey for diverse natural enemy complexes. I. liriodendri supports Coccinellidae (comprising >95% of predators with positive numerical response to aphid density), parasitoids in Hymenoptera: Aphidiinae and Aphelinidae, and the native European endoparasitoid Areopraon silvestre (Braconidae). The genus functions as a herbivore in plant-insect food webs and as a prey resource for arthropod predators and parasitoids.

I. liriodendri is considered the most important insect pest of tuliptree in urban landscapes, with heavy infestations significantly impacting young trees despite mostly aesthetic effects. I. pepperi is an agricultural pest of blueberry. The invasive spread of I. liriodendri in Europe has prompted biological control research and monitoring. Some species serve as study organisms for predator-prey interactions and temperature effects on biological control.

• MetopeurumIllinoia has been treated as a synonym of Metopeurum in some taxonomic treatments (Catalogue of Life), but is accepted as distinct in GBIF and other sources; separation requires examination of taxonomic authority and current classification systems.
• Other Macrosiphini generaShared tribal characteristics including long antennae and siphunculi; species-level identification within Illinoia and separation from related genera requires host association data and detailed morphological or genetic analysis.

• aphid
• Macrosiphini
• phloem-feeder
• pest insect
• ornamental pest
• agricultural pest
• invasive species
• biological control
• honeydew producer

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Illinoia liriodendri . [Distribution map].
• Tuliptree Aphid Scientific Name: Illinoia liriodendri (Monell) (Insecta: Hempitera: Aphididae)
• Phenology, population trends and natural enemy complex of Illinoia liriodendri in Spain
• DISTRIBUTION AND SEASONAL PHENOLOGY OF BLUEBERRY APHIDS (ILLINOIA PEPPERI (MACG.)) IN MICHIGAN
• Genetic identification of new alien pest species Illinoia liriodendri and its parasitoid Areopraon silvestre in Croatia
• Natural Enemies of the Pea Aphid (Illinoia Pisi Kalt.); Their Abundance and Distribution in Wisconsin
• Genetic identification of new alien pest species Illinoia liriodendri and its parasitoid Areopraon silvestre in Croatia
• Survey of the parasitoids of the tuliptree aphid,Illinoia liriodendri (Hom: Aphididae), in northern California
• The Lacewings Micromus angulatus and Chrysoperla carnea as Predators of the Rhododendron Aphid, Illinoia lambersi, Under Different Temperature Regimes.