Lomachaeta vacamuerta Williams & Pitts, 2009

Williams, Kevin A., Cambra, Roberto A., Bartholomay, Pedro R., Luz, David R., Quintero, Diomedes & Pitts, James P., 2019, Review of the genus Lomachaeta Mickel, 1936 (Hymenoptera: Mutillidae) with new species and sex associations, Zootaxa 4564 (1), pp. 101-136 : 130-131

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Lomachaeta vacamuerta Williams & Pitts, 2009


Lomachaeta vacamuerta Williams & Pitts, 2009

( Figs 2, 3 View FIGURES 1–4 , 6, 7 View FIGURES 5–8 , 64 View FIGURES 61–64 )

Lomachaeta vacamuerta Williams & Pitts, 2009: 239 . Holotype, ♂, USA, New Mexico, Chaves Co. (EMUS).

Lomachaeta vacamuerte Williams & Pitts, 2009: 242 . lapsus calami.

Diagnosis. MALE. This species can be immediately recognized by the unique genitalia, wherein the paramere is straight, subcylindrical, and having an apical tuft of long setae. The following characters are also useful for diagnosis: the body is entirely blackish, except the sometimes reddish tegulae; the mandible is unarmed ventrally; the gena is ecarinate; the forewing has its veins encompassing the basal 0.7 × of the wing; the T1 shape is subsessile; the head and T2 disc have separated punctures; and the T2 fringe is composed of simple setae. Body length 5–6 mm.

FEMALE. This species can be recognized by the setae and mesosoma shape: the mesosomal dorsum and T2 disc have matching thickened posteriorly-directed subparallel appressed pale golden setae and the mesosoma is elongate, with the thoracic dorsum nearly as long as wide. Additional useful diagnostic features include: the mandible has a barely perceptible ventral lamella that does not interrupt the ventral mandibular contour; the head is clearly broader than the mesosoma; the T2 fringe is sparse and simple; and the S6 lateral carina is raised, rounded.

Description. FEMALE (hitherto unrecognized, based on female from Kennedy County). Body length 3 mm. Coloration. Head, mesosoma, antenna, legs, and T6 predominantly dark brown; metasoma and bases of leg segments and antenna orange. Tibial spurs white. Body setae whitish yellow, except frons, mesonotum, and T6 with many erect setae darkened, at least apically. Mesonotum and T2 disc with long thick posteriorly-directed subparallel setae; fringes of T2–3 composed of dense thick subappressed simple white setae; fringes of T4–5 setae sparse, simple. Head. Head width 1.2 × pronotal width. Frons, vertex and gena areolate, vertex with some intervals obliterated. Clypeus without distinct teeth or ridges. Genal carina extending anteriorly nearly to hypostomal carina. Mandible oblique, tapering, bidentate apically, with shallow lamella baso-ventrally that does not interrupt the ventral mandible contour. Antennal scrobe without dorsal carina. Lengths of F1 and F2 each subequal to pedicel length. Mesosoma. Mesosoma elongate; dorsal thoracic length 0.95 × width. Humeral carina distinct, angulate dorsally, not reaching epaulet. Mesosomal dorsum areolate; intervals clearly defined, not raised into tubercles; areolations slightly tighter anteriorly than posteriorly; dorsally with 12 areolations between pronotal spiracles. Pronotal and propodeal spiracles weakly swollen; lateral mesonotal tubercle weakly defined. Lateral propodeal face impunctate. Metasoma. T1 shape sub-disciform, punctate. T2 slightly longer than wide. Disc of T2 with dense oblique punctures, intervals smooth. T3–5 and S2–5 with separated punctures, intervals obscure microreticulate. T6 convex. Incomplete lateral S6 carina rounded, raised.

Material examined. USA, Arizona, Pima County, 550m, Silver Reef Wash, 4 km E. Vaiva Vo, Tat Momoli Mountains , malaise, 1–7.V.2006, M. E. Irwin (1♂, EMUS, Fig. 64 View FIGURES 61–64 ) ; Texas: Kennedy County, 2.5 mi. S Sarita, 18–20.X.2002, B. Raber & E. Riley, pit-fall in sand (1♀, TAMU, Figs 3 View FIGURES 1–4 , 7 View FIGURES 5–8 ); LaSalle County, Chaparral Wildlife Management Area , 13 mi. SW Cotulla, 28.293°N 99.383°W, 19.V.2006, J.S. Wilson and K.A. Williams (2♀, CSCA EMUS, Figs 2 View FIGURES 1–4 , 6 View FIGURES 5–8 ) GoogleMaps .

Distribution. Widespread in the western Nearctic, including Arizona, California, New Mexico and Texas ( USA) and Sonora ( Mexico).

Remarks. This widespread species has variably colored tegulae in males. In Arizona and California, this species has orange tegulae, resembling the sympatric L. cirrhomeris ( Fig. 42 View FIGURES 41–46 ), L. ilex ( Fig. 61 View FIGURES 61–64 ), and L. litosisyra ( Fig. 63 View FIGURES 61–64 ); farther East, the males are uniform blackish.

The putative sex association presented here is based on a process of elimination. Lomachaeta hicksi and L. vacamuerta are the only Lomachaeta species known from southern Texas and the female of L. hicksi is distinct (in nearly all species-level characters) from the females described above.

The female from Kennedy County ( Fig. 3 View FIGURES 1–4 ) has different coloration than the two females from LaSalle County ( Fig. 2 View FIGURES 1–4 ). It is the only Lomachaeta we have seen with a dark head and mesosoma that contrast with an orange metasoma, a pattern rarely seen in mutillids, except among Dasymutilla Ashmead and Pseudomethoca Ashmead from the Texan mimicry ring ( Wilson et al., 2015). If natural selection has favored the similarities of this species to the Texan mimicry ring, various hypotheses could explain its limited mimetic fidelity. These include phylogenetic constraints of the genus Lomachaeta , the relaxed selection hypothesis based on its small size ( Penney et al., 2012), or the community diversity hypothesis based on presence of multiple potential models ( Wilson et al., 2013).


Texas A&M University


California State Collection of Arthropods














Lomachaeta vacamuerta Williams & Pitts, 2009

Williams, Kevin A., Cambra, Roberto A., Bartholomay, Pedro R., Luz, David R., Quintero, Diomedes & Pitts, James P. 2019

Lomachaeta vacamuerta

Williams, K. A. & Pitts, J. P. 2009: 239

Lomachaeta vacamuerte

Williams, K. A. & Pitts, J. P. 2009: 242