Taxonomically-difficult
Guides
Acmaeodera
Acmaeodera is a large genus of jewel beetles (family Buprestidae) with over 150 species in North America, reaching greatest diversity in the desert southwest and Mexico. Adults are metallic, often with distinctive color patterns, and are frequently observed visiting flowers to feed on pollen. The genus is distinguished by unique flight morphology: elytra are fused along the midline and remain closed during flight, functioning as a protective shield over the abdomen while only the hindwings provide propulsion. This trait, combined with abdominal banding in many species, creates a wasp-like appearance in flight and has led to recognition of several species as hymenopteran mimics. Larvae are wood-borers in twigs and branches of various woody plants.
Buprestidaejewel-beetlesmetallic-wood-boring-beetlesflower-visitorspollen-feederselytra-fusionflight-morphologyhymenopteran-mimicrywood-borersNorth-AmericaMexicoArizonaTexasCaliforniaNew-MexicoOklahomaAlbertaAsteraceaeCercocarpusspring-activemonsoon-activefall-activetaxonomically-difficultcollector's-itemdiurnalCerceris-preyAcmaeodera conoidea
Acmaeodera conoidea is a small metallic wood-boring beetle in the family Buprestidae, described by Fall in 1899. It belongs to the 'tubulus-species group' within the genus, characterized by small size (<8 mm), black coloration with yellow maculations on the elytra, and membership in the 'Truncatae' group (species with prosternal margin nearly straight). The species occurs in the south-central and southwestern United States. Like other members of its species group, it is difficult to identify without comparison to determined specimens due to the lack of modern revisionary work on the genus.
Acmaeoderini
Acmaeoderini is a tribe of metallic wood-boring beetles (family Buprestidae, subfamily Polycestinae) comprising at least 4 genera and more than 560 described species worldwide. The tribe includes the hyperdiverse genus Acmaeodera, which accounts for approximately three-fifths of North American jewel beetle diversity. Members are characterized by metallic coloration and are taxonomically challenging due to extreme intraspecific variability and poorly defined species limits. Larvae are predominantly wood-borers with documented associations across multiple plant families, while adults are frequently anthophilous.
Ageniella faceta
Ageniella faceta is a species of spider wasp in the family Pompilidae, first described by Cresson in 1872. It belongs to the 'accepta species group' within the genus Ageniella, which includes morphologically similar species that are difficult to distinguish without expert examination. The species has been historically confused with A. accepta and A. conflicta due to overlapping characteristics and limited diagnostic resources.
Apamea cuculliformis
Apamea cuculliformis is a noctuid moth species described by Augustus Radcliffe Grote in 1875. It belongs to the diverse cutworm moth genus Apamea, a group noted for taxonomic difficulty due to individual variation and overlapping morphological traits among species. The species is endemic to western North America. Available information is limited to basic taxonomy and geographic distribution.
Apamea lutosa
opalescent apamea, Opalescent Apamea Moth
Apamea lutosa is a noctuid moth commonly known as the opalescent apamea. It is distributed across central and eastern Canada and the north-eastern United States. The species is part of the taxonomically challenging genus Apamea, whose members are often difficult to distinguish visually. Larval feeding has been documented on quackgrass (Elytrigia repens).
Cerotainiops mcclayi
Cerotainiops mcclayi is a species of robber fly (Family Asilidae) described by Martin in 1959. The genus Cerotainiops contains small, slender robber flies often associated with sandy or open habitats. Members of this genus are characterized by their elongated body form and reduced wing venation compared to larger asilid genera. This species is part of a group of diminutive robber flies that are frequently overlooked due to their small size and cryptic behavior.
Enicospilus
Enicospilus is a megadiverse genus of large ichneumonid wasps comprising over 700 described species worldwide. Members exhibit 'ophionoid facies' with orange-brown bodies, extremely large ocelli arranged in a triangle, and long antennae. These wasps are unusual among Hymenoptera for their nocturnal or crepuscular activity and strong attraction to artificial lights. They are koinobiont endoparasitoids of moderately large lepidopteran larvae, including families such as Lasiocampidae, Noctuidae, and Saturniidae. Species delimitation is notoriously difficult due to limited diagnostic morphological characters, resulting in frequent taxonomic confusion including synonyms and misidentifications.
Euconnus rasus
Euconnus rasus is a minute rove beetle in the subfamily Scydmaeninae, first described by John Lawrence LeConte in 1852. Members of this genus are among the smallest beetles, typically measuring under 2 mm. The species has been recorded across northeastern North America, with scattered observations in the Great Lakes region and Atlantic coastal states. Like other scydmaenines, it likely inhabits leaf litter and other decaying organic matter, though specific ecological details remain poorly documented.
Eupithecia absinthiata
Wormwood Pug
Eupithecia absinthiata, commonly known as the Wormwood Pug, is a small moth in the family Geometridae. It belongs to the large genus Eupithecia, whose members are often called 'pugs' and are recognized by their narrow wings and distinctive resting posture. The species has been documented as a nocturnal visitor to apple flowers, contributing to pollination services. It occurs across the Palearctic region, the Near East, and North America.
Gnoristinae
fungus gnats
Gnoristinae is a subfamily of fungus gnats within the family Mycetophilidae. As of 2019, over 442 species have been described across more than 30 genera, making it one of the most taxonomically challenging groups in Mycetophilidae with species and generic boundaries subject to frequent revision. The subfamily has been characterized as highly diverse with new taxa described annually from various parts of the world. Members are generally small flies, with some species reaching only 3 mm in body length.
Idiocerus
Idiocerus is a large genus of leafhoppers in the family Cicadellidae, first described by Lewis in 1834. The genus is taxonomically challenging, with many species exhibiting similar morphology that complicates identification. Species are predominantly associated with woody host plants, particularly poplars (Populus) and willows (Salix), though some species have been documented as pests of mango (Mangifera indica) in India. The genus has a broad distribution across the Holarctic region, with numerous species in both Europe and North America.
Myzinum
New World Banded Thynnid Wasps
Myzinum is a genus of thynnid wasps containing approximately 63 recognized species, with 10 species occurring in North America. Adults measure 7–24 mm and exhibit extreme sexual dimorphism: males are slender with long, straight antennae and a prominent curled pseudostinger at the abdomen tip, while females are robust with short, coiled antennae and stout legs adapted for digging. These wasps are parasitoids of scarab beetle grubs, particularly Phyllophaga species, and are used as biological control agents. They are most diverse in the Neotropics and are commonly observed visiting autumn wildflowers such as goldenrod and thoroughwort.
Scydmaenus
ant-like stone beetles
Scydmaenus is a genus of minute rove beetles in the subfamily Scydmaeninae, commonly called ant-like stone beetles. The genus has nearly cosmopolitan distribution with species documented across Europe, Asia, Africa, Australia, and other regions. Members are small, slow-moving beetles typically found in soil and leaf litter habitats. Some species have been documented as predators of soft-bodied arthropods, though earlier literature suggested specialization on armored mites.
Strongylium
darkling beetles
Strongylium is a large genus of darkling beetles (Tenebrionidae: Stenochiinae) containing more than 1,400 described species, making it one of the most species-rich genera in both the family and subfamily. The genus exhibits a broad tropical and subtropical distribution across the Old and New Worlds, with particularly high diversity in the Neotropics (over 300 species). Species-level identification is challenging due to the genus's size and morphological diversity, often requiring specialist knowledge or detailed examination.
Thyreodon umbrifer
Thyreodon umbrifer is a species of ichneumon wasp described by Porter in 1989. The genus Thyreodon belongs to the family Ichneumonidae, one of the largest families of parasitoid wasps. Very little published information exists about this specific species. A specimen initially identified as possibly belonging to this genus was observed in Arizona, where experts noted difficulty distinguishing Thyreodon from related genera in the southwestern United States. The genus is poorly known taxonomically, and species-level identification requires specialist examination.