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Order Strepsiptera - Twisted-winged Insects

Strepsiptera? - Xenos peckii Strepsiptera - Halictophagus - male Polistes aurifer assymetry - Xenos peckii - female Strepsiptera found in malaise trap...Corioxenidae? - male 3rd time's a charm - Halictoxenos ID of parasite on Andrena Bee - Stylops Strepsiptera on Zethus spinipes - Eupathocera - female Male strepsipterans (Eupathocera lugubris) recently eclosed from a male Ammophila pictipennis - Eupathocera lugubris - male
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Strepsiptera (Twisted-winged Insects)
Synonyms and other taxonomic changes
probably sister to beetles(1) and used to be included in beetles by some workers(2)
Explanation of Names
Strepsiptera Kirby, 1813
'twisted wing'
~91 spp. in 14 genera of 6 families arranged in a single suborder (Stylopidia) in our area(3)(4)
~630 spp. in 43 genera of 15 families (10 extant) worldwide,(5)(4) arranged in 2 suborders, Mengenillidia (3 extant families) and Stylopidia (8 families)(6)(7)

Overview of our fauna of Strepsiptera
(* denotes taxa not yet in the guide)

Order Strepsiptera
Suborder Stylopidia
Family Corioxenidae
Subfamily *Corioxeninae *Floridoxenos (1 sp.), *Loania (1 sp.)
Subfamily Triozocerinae Triozocera (2 spp.)
Subfamily Halictophaginae Halictophagus (12 spp.)
Family *Elenchidae
Subfamily *Elenchinae *Elenchus (1 sp.)
Family *Myrmecolacidae *Caenocholax (1 sp.)
Family Stylopidae *Crawfordia (4 spp.), *Eurostylops (4 spp.), Halictoxenos (5 spp.), *Hylecthrus (1 sp.), Stylops (37 spp.)
Family Xenidae Eupathocera (6 spp.), Leionotoxenos (10 spp.), Xenos (6 spp.)
0.5-4 mm(8)
Adult females are larviform/neotenic endoparasites; adult males are free-living, and their sole mission is to find and fertilize a female. They have reduced forewings and fan-shaped hind wings, branched antennae, and raspberry-like eyes, unique among living insects and somewhat similar to the eyes of trilobites.(7)

Key to families (adult males) by Kathirithamby & Taylor (2005).(3) See further taxonomic work by Pohl (2002) and Benda et al. (2022) on the overlooked separation of Stylopidae and Xenidae.
Suborder Stylopidia is cosmopolitan (2 families of 2 spp. each are restricted to the Neotropical and Oriental regions, respectively)
Suborder Mengenillidia is an Old World group(7), the recently discovered monotypic Bahiaxenidae is a "living fossil" from Brazil(5)
obligate parasites of insects (hosts include members of 7 orders and 34 families)(7)
Life Cycle
Apart from the adult males, the only free-living stages are the viviparous 1st instar host-seeking larvae(7); the larvae hatch as free agents from eggs laid on flowers. When a suitable host visits the flower, the larva attach itself to it and become parasitic.(8)
Print References
Benda D, Pohl H, Nakase Y, Beutel R, Straka J (2022) A generic classification of Xenidae (Strepsiptera) based on the morphology of the female cephalothorax and male cephalotheca with a preliminary checklist of species. ZooKeys, 1093: 1-134. DOI: 10.3897/zookeys.1093.72339
Pohl, H (2002) Phylogeny of the Strepsiptera based on morphological data of the first instar larvae. Zoologica Scripta, 31(1): 123-134. DOI: 10.1046/j.0300-3256.2001.00078.x
Internet References
Fact sheet from Virginia Tech(9) (Web Archive) - taxonomy is out of date