Microrhopala arizonica Schaeffer

Riley, Edward G., 2019, On the status of Microrhopala arizonica Schaeffer (Coleoptera: Chrysomelidae Cassidinae: Chalepini), Zootaxa 4686 (1), pp. 133-139 : 136-137

Microrhopala arizonica Schaeffer , species status restored

( Figs 2 , 9–13, Map 1 )

Microrhopala arizonica Schaeffer 1906: 252 [original description]

Type Locality: USA: Arizona State: Huachuca Mountains .

Pentispa suturalis : [citations using this name for material from Arizona apply to this species; see Staines (2015) for numerous citations].

Type material: Lectotype ( Fig 2 ) here designated, sex undetermined, labeled “type || Huach Mts. | VI-18 Ariz. || BROOKLYN | MUSEUM | COLL 1929 || [red label] TYPE USNM | 42330 || Microrhopala | arizonica | type. Schffr || [red-double-lined-bordered label] Penthispa | suturalis | Baly || USNMENT | [matrix barcode] | 0091181”. Conserved in USNM, in excellent condition with all appendages intact. Schaeffer (1906) did not indicate a type, and since he did not state the number of specimens before him and nothing provided in the work implies that he had more than one specimen, that number cannot be definitively determined. Staines & Staines (1997) referenced the specimen cited above as “… a unique holotype specimen …” but this is incorrect since Schaeffer did not indicate a “type” nor did he reference a single specimen ( ICZN Art. 73.1, 73.1.1). This “ holotype ” reference could be inter- preted as a lectotype fixation by inference ( ICZN Art. 74.6) if not for the uncertain number of original specimens. To eliminate confusion and fix the application of this name, a lectotype is here designated. Repositor(ies) of possible paralectotypes unknown.

Remarks: The important work on the biology and the larval description for Pentispa suturalis by Bolt & Staines (1993) actually applies to Microrhopala arizonica . No specimens from México were seen during this study, although it must certainly occur there, at least in areas adjacent to southeastern Arizona.

Other specimens examined (79 total):

UNITED STATES: Arizona: Cochise Co. near Portal, VIII-25-1970, S. McCleve, sweep net [1 TAMU]; 2 mi. SW Portal, Cave Creek Canyon, Chiricahua Mts., 5000’ V-29-2009, H. A. Hespenheide [5 TAMU]; 6 mi. W Portal, Cave Creek Canyon, Chiricahua Mts., 31°55’N, 109°15’W, 6700’, VIII-20-1980, H. A. Hespenheide [2 TAMU]; same locality, IX-8-1980, H. A. Hespenheide, Selloa [1 TAMU]; Southwestern Res. Station, Cave Creek Canyon, Chiricahua Mts., 31°53’N, 109°12’W, 5350’, VII-4-1981, H. A. Hespenheide, Selloa [1 TAMU]; same data, except, VII-5-1981 [1 TAMU]; same data, except VII-7-1981 [1 TAMU]; same locality, VI-22-1984, H. A. Hespenheide [1 TAMU]; same locality, VI-23-1984, H. A. Hespenheide, Selloa [1 TAMU]; same locality, VII-11-1996, H. A. Hespenheide [1 TAMU]; Ash Canyon, Huachuca Mts., IX-22-1999, P. E. Bolt & T. O. Robbins, feeds on leaves Baccharis bigelovii [2 TAMU]; Huachuca Mts., Carr Canyon, VII-24, 29 -1984, D. A. LaRue [7 EGRC]; same locality, VIII-7-1983, C. Bellamy [6 TAMU]; same locality, IV-28-1994, T. O. Robbins, host: Baccharis bigelovii [10 TAMU]; Carr Canyon, Huachuca Mts., 31.446°N, 110.284°W, VII-23-2017, S. M. Clark, on Baccharis bigelovii A Gray [32 EGRC]; Corondo Nat’l. Forest, VI-30-1984, W. B. Warner [1 EGRC]; Coronado Nat’l. Memorial, Huachuca Mts., IV-24-1991, T. O. Robbins, feeds on leaves Baccharis bigelovii [1 TAMU]; Huachuca Mts., Miller Canyon, IX-9-10-1968, Don Roger Harris [3 EGRC]; same locality, IX-8-1979, S. McCleve [1 TAMU]; Pelocillo Mts., 33 mi. E Douglas, VII-17-1973, S. McCleve [1 EGRC].

Comparative remarks: As note above, these two species are similar in general appearance and this led to them being incorrectly synonymized by Wiese (1911a) who may have never seen both species together. They are easily separated by their general habitus (compare Figs 1 , 3 and 2, 4). As is characteristic of species of Microrhopala , M. arizonica has the elytral apices broadly evenly rounded (Fig. 12), whereas P. suturalis has the elytral apices more abruptly rounded (Fig. 6) resulting in a more cuneiform body shape which is typical of most Pentispa species.

There is slight color variation in both species. The black median pronotal spot is variably developed in both species, and sometimes absent in P. suturalis . The small dark humeral spot of P. suturalis is absent in some specimens. The width of the dark sutural vitta in P. suturalis is usually confined to the sutural interval, but in the specimen from Chipinque Mesa, Nuevo León it is fairly broad, reaching to the second punctate stria. Body length (excluding antennae) of P. suturalis is on average smaller than that of M. arizonica , 3.6–4.5 mm (ave. 4.0, n=17) verse 3.9–4.7 (ave. 4.4, n=20) for M. arizonica .

There are no differences of importance between these species in the sculpture of the vertex (compare Figs 5 and 11), as both species possess a strong median groove with a deep groove to each side, with each of these lateral grooves containing multiple elongate punctures. There are also no differences of importance in the shape and delimitation of the clypeus, both species have the base slightly raised and evenly rounded to its lateral corners that do not project outward. Both species also possess an elytral ground-plan of eight punctate striae on each elytron. Staines (2006) in his key to genera (p. 6) incorrectly ascribes ten punctate striae to the genus Pentispa , but members of this genus have only eight. The raised elytral costate are slightly different between the two species. While both tend to have intervals II and IV more strongly developed than intervals I and III, the disparity is greater in M. arizonica . A final difference noted between these species involves the development of the raised tooth-like formation found before the articulation-point of the claws on the ventral surface of last tarsomere. This formation is present and well developed in P. suturalis , represented by a split, v-shaped structure with the apex of each arm tooth-like (Figs 7- 8, arrows) whereas it is entirely lacking in M. arizonica (Fig. 13). The absence of this structure in M. arizonica is unusual, since a cursory examination of other species of Microrhopala , Pentispa , and a broad selection of species representing other genera of the Chalepini reveals that it is present in one form or another. Microrhopala arizonica will key to Microrhopala in both Staines (2006) and Riley et al. (2002), and P. suturalis will key to Pentispa in Riley et al. (2002) .

Discussion of generic relationships: The genera Microrhopala and Pentispa are very close and are in need of taxonomic reassessment. Both contain species occurring south of the United States and, in the case of Pentispa , most species are found there. Both genera use Asteraceae as larval hosts ( Clark et al. 2004, Staines 2015) but ad- ditional host families are recorded for some tropical Pentispa ( Staines 2015) . Clark (1983) and Riley et al. (2002) noted that Mirorhopala can be divided into two morphological groups with Microrhopala proper, type species M. vittata (F.), distinct from most other included species which are morphologically close and probably inseparable from some Pentispa . Most Pentispa are separable from Microrhopala only by their habitus as noted above for M. arizonica and P. suturalis and by their general body form with tends to be flatter with more sharply defined costate. These generic concepts are perpetuated in the present work, however it should be noted that the slight difference in body form, such as that seen between the two species treated here, hardly seems adequate justification for recognizing two separate genera. Some species assigned to Pentispa have a habitus that is very close to that of Microrhopala while in others it can be strikingly different having the elytral apices broadly foliate, heavily spined or conjointly emarginate at the suture. Some Pentispa have a unique clypeal structure that is not present in Microrhopala where the base is strongly raised, shelf-like, and the lateral corners are angulate and projected. The claw character noted above for M. suturalis is present in the other three species of Pentispa recorded from the United States and this structure, or some form of this structure, is present in the other United States species of Microrhopala .

Figures

MAP 1. Pentispa suturalis (Baly) (▲), Microrhopala arizonica Schaeffer (●). Based on specimens examined and localities cited by Baly (1886), Champion (1894) and Weise (1905).

FIG. 1. Chalepus suturalis Baly, lectotype and labels. Fig. 2. Microrhopala arizonica Schaeffer, lectotype and labels. Figs 3-8, Pentispa suturalis (Baly), 3) dorsal habitus [Valle de Bravo, México] 4), antenna, 5) vertex of head, 6) elytral apices, 7) fourth tarsomere, lateral, 8) fourth tarsomere, oblique-ventral (arrows indicate tooth). Figs 9-13, Microrhopala arizonica Schaeffer, 9) dorsal habitus [Carr Canyon, Arizona], 10) antenna, 11) vertex of head, 12) elytral apices, 13) fourth tarsomere, oblique-lateral. Habitus images to scale bar; comparable body-part images to scale, respectively.