Genus Tachytes

This key is constructed from a key in the paper Larrinae of Kansas, from F. X. Williams in the 1913 Kansas University Science Bulletin (Copy thanks to Mark O'Brien in Michigan). It is missing several species that may occur in Arkansas but have not been proven for the state. In the females they are: Tachytes auricomans Bradley, Tachytes columbiae Fox, Tachytes crassus Patton, Tachytes harpax Patton, Tachytes parvus Fox, Tachytes pennsylvanicus Banks, and Tachytes praedator Fox. These species likely appear in an updated key by Bohart in 1994 but I don't have access to this yet. The male key below is even further decimated. 



1  Anterior margin of clypeus produced in the middle into a rather narrow lobe, lateral margins of clypeus distinctly dentate; legs ferruginous


1' Anterior margin of clypeus not produced into a lobe; legs black



2 Pygidium scarce constricted preapically, covered with fine golden pile

validus Cresson

most of east


2 Pygidium somewhat constricted before apex, its bristles bronzy

aurulentus (Fabricius)

US west to AZ WY


3 Clypeus armed with a long prong on either side; pygidium triangular, with rather sparse, stout, appressed bristles which are golden or silvery

mergus W. Fox

NJ to FL west to OK TX


3 Clypeus without a lateral prong; pygidium well bristled



4 Clypeus rounded out, armed laterally with more or less distinct teeth; abdomen black or black and ferruginous



4 Clypeus without teeth; abdomen black with brassy or silvery fasciae; wings light fuscous

obductus W. Fox



5 Metatibiae with at least the basal half of outer posterior row of spines short, blunt and thorn-like, the row much shorter than those on the first joint of the hind tarsi, and usually extending to quite near the base of the tibiae; pygidium (at least in fresh specimens) with some erect hair in addition to the fine appressed pile; species rather small



5 Metatibiae with the spines not short as in the above, usually well pointed and differing but little from those of the first joint of the hind tarsi, and usually ending (or beginning) at a good distance before the base of the tibiae; no erect hair on pygidium, the latter golden or bronzy



6 Mandibles very narrowly notched exteriorly; black species

chrysopyga obscurus Cresson



6 Mandibles with the notch normal; the first two or three segments of the abdomen ferruginous

abdominalis Say




7 Abdomen in part red

amazonus F. Smith




7 Abdomen entirely black



8 Abdomen with four silvery fasciae; wings hyaline; legs black

pepticus (Say)

US west to AZ, S. CA


8 Abdomen 3-fasciate; wings yellowish, dark apically; legs ferruginous

distinctus F. Smith



Males (see species distributions above for males)


1  Fore coxae simple; fore femora near the base entire


1' Fore coxae with an elongate posterior process; fore femora beneath near the base emarginate



2 Flagellum with the basal joints distinctly rounded out beneath; thorax with long and rather dense golden pubescence; legs partly ferruginous



2 Flagellum with the basal joints not or very slightly rounded out beneath; the long pubescence of thorax not dense; legs black



3 Pygidium with pile largely suberect; small black species



3 Pygidim with pile all appressed; usually larger species



4 Wings yellow, their apical portion dark, abdomen black



4 Wings pale yellowish hyaline, not dark apically; abdominal segments 1 and 2 usually fulvous; small species



Family Key