Key to the Species of Nigrotomocoris

1. Tibiae and antennal segment II pale yellowish brown; distribution: San Luis Potosi, Mexico ........ tibiopallidus (Carvalho)

– Legs and antennal segment II uniformly black................................................................2

2. Larger species, length 3.24–3.88 mm; head with a broad pale yellowish-brown fascia across base; basal half of antennal segment II distinctly thicker than apical half; labium relatively short, extending to middle coxae; genital tubercle stout (Fig. 133), broadly rounded apically; distribution: Oaxaca and Puebla, Mexico ................................ nigrus (Carvalho)

– Generally smaller species, length 3.00– 3.36 mm; head uniformly black, at most, with a narrow, indistinct yellowish-brown fascia across base; antennal segment II uniformly slender; labium extending at least to bases of hind coxae; genital tubercle more slender, apically pointed (Figs. 131, 132)...................................................................3

3. Length of antennal segment II subequal to or greater than interocular width; pro-, meso-, and metapleural areas of thorax uniformly black; genital tubercle (Fig. 132) conical; distribution: Puebla, Mexico ...................... .. longirostris, n. sp.

– Length of antennal segment II much shorter than interocular width; pro-, meso-, and metapleura each with a large circular or elongate-oval dirty white patch; genital tubercle (Fig. 131) spinelike, more elongate and apically acute; distribution: Durango, Mexico ................................................................................... keltoni, n. sp.