Acanthocaudus tissoti (Smith)

(Figs 3–4, 6–7)

Trioxys (Acanthocaudus) tissoti Smith, 1944: 96 [USNM, examined].

Acanthocaudus tissoti: Mackauer 1960: 138 [revised combination].

Trioxys (Acanthocaudus) schlingeri Muesebeck, 1958: 144 [USNM, examined]. New synonym. Acanthocaudus schlingeri: Mackauer 1960: 138 [revised combination].

Diagnosis. The mesosoma is mottled yellow and brown or entirely brown in A. tissoti; it is entirely yellow in A. caudacanthus . The head is entirely brown or brown dorsally and gradually transitioning to yellow ventrally in A. tissoti; it is yellow with ocellar triangle entirely brown to black or yellow with brown to black markings around periphery of each ocellus in A. bicolor .

Distribution. CANADA: British Columbia (Schlinger & Hall 1960); CUBA: Guantánamo (as Oriente), Pinar del Río (Starý 1981); USA: Florida (Smith 1944), Indiana *, South Dakota (Assefa et al. 2015).

Hosts. Uroleucon (Uroleucon) ambrosiae (Muesebeck 1958) ex Baccharis sp. (Schlinger & Hall 1960) and Parthenium hysterophorus (Starý 1981), Uroleucon (Uroleucon) rudbeckiae (Smith 1944) ex Silphium perfoliatum, Uroleucon (Uroleucon) russellae (Marsh 1979) .

Specimens reared. All USA. INDIANA: 1 ♀ Tippecanoe Co., Lily Wildlife Area, 40°23'15.26"N 86°56'11.30"W, 2.vii.2007, T.T. Heidel, ex undet. aphids on Silphium perfoliatum, 07-254 ; 1 ♀ same data as previous except 07-296; SOUTH DAKOTA: 3 ♀ 21 ♂ Brookings Co., Brookings, South Dakota State University, Campus Agronomy Farm, 1.viii.2001, P. Loewe & A. Boe, ex aphids on Silphium perfoliatum; 15 ♀ 12 ♂ 5 indet. same data as previous except Felt Farm, 4 mi N of Brookings, 44°22'08"N 96°47'39"W, 1693' elevation, coll. 28.vii.2013, A. Boe, em . 28.vii.–2.viii.2013, ex Uroleucon cf. rudbeckiae on Silphium perfoliatum; 20 ♀ 20 ♂ 1 indet. same data as previous except coll. 3.viii.2013, P. J. Johnson, em . 3–4.viii.2013; 1 ♀ same data as previous except coll . 15.viii.2013, em. 17–20.viii.2013 (1 ♀ PURC, 10 ♀ 10 ♂ SDSU, 30 ♀ 43 ♂ 6 indet. USNM).

Discussion. Muesebeck (1958) differentiated A. schlingeri (Figs 4, 7) from A. tissoti (Figs 3, 6) based on the absence of a distinct carina mediobasally on the propodeum and the eyes more convergent ventrally in the former compared to the later. Analysis of 31 female specimens from South Dakota regarded as A. tissoti by the first author revealed that the carina mediobasally on the propodeum varies from present to absent within this species. Also, FW was 1.40–1.67X FH for 26 of the female specimens from South Dakota regarded as A. tissoti . The FW:FH ratio for the holotypes of A. tissoti and A. schlingeri are 1.42 and 1.43, respectively, and thus, both fall within that range. Therefore, Acanthocaudus schlingeri Muesebeck, 1958 is synonymized with Acanthocaudus tissoti (Smith, 1944) given the intraspecific variation observed for the features used to distinguish those species.