Polyphylla mescalerensis Young 1988

(Fig. 48–49)

Remarks. Based on a series of 19 males, Young (1988) described P. mescalerensis from the Mescalero Sand Dunes, Chaves County, New Mexico. The female was subsequently described by La Rue (1998).

In Young’s key to the North American species of Polyphylla (1988), the concluding couplet for P. mescalerensis (#18, p.24) includes the distributional note, “ Chihuahua, Mexico.” Inexplicably, no further reference to the Chihuahuan record appears anywhere in the publication nor, in the intervening years since Young’s publication, have any supporting references documenting its occurrence there been reported (Morón 1997, 2010, 2015 in litt.).

A purported male specimen of P. mescalerensis examined is labeled “ MEX: Chihuahua, Cerro San Luis, VIII-13-1981, 1767m at light, S. McCleve // P. mescalerensis Young, det. R. M. Young 1988 ” (DALC). The coincidental year of Young’s determination suggests the possibility that this was a specimen on which he validated the Chihuahuan distributional record.

Upon closer scrutiny, however, the Cerro San Luis specimen and samples from the Mescalero Sand Dunes differ in several salient morphological respects as follows:

Mescalero Sand Dunes, New Mexico. (15 male topotypes) (Fig. 48). Dorsal integument light yellowishbrown to reddish-brown except head black; anterior clypeal margin moderately reflexed, lateral margins basally convergent; distal maxillary palpomere-4 conical, obtusely tapered at apex, surface coarsely punctate, with only a few randomly scattered golden setae; scutellum narrow, triangular; pronotum widest at basal 1/2, margins strongly explanate, discal setae sparsely to moderately distributed; elytral disc setose or glabrous (abrasion), posterior margins obtusely rounded; protibia bidentate to tridentate; meta-, mesotibia with two or three acuminate projections; antennae small, slightly to deeply recurved distally; ventral surface of protarsomere-5 smooth, lacking any serration.

Cerro San Luis, Chihuahua, Mexico. (1 male) (Fig. 49). Dorsal integument deep reddish brown except head, lateral pronotal disc, and elytral humeri black; anterior clypeal margin weakly reflexed, lateral margins parallel; distal maxillary palpomere-4 acutely tapered at apex, feebly depressed dorsally, surface finely punctate, with very fine, short pale setae; scutellum transverse; pronotum widest at basal 1/3, margins feebly explanate, discal setae sparsely distributed; elytral disc glabrous, posterior margins recurved inward toward sutural apices; protibia bidentate, lacking any indication of a basal third tooth; meta-, mesotibia devoid of acuminate projections; antennae large, moderately recurved distally; ventral surface of protarsomere-5 with a raised serrated carina.

Given the marked disparity of morphological and ecological factors and the absence of additional specimens confirming its occurrence there, the Chihuahuan record for P. mescalerensis is invalidated. Because only a single Cerro San Luis specimen is presently known, definitive taxonomic treatment must await additional material.