Megacyllene, Casey, 1912

Hart, Charles J. & Ivie, Michael A., 2013, Synonymy ofMegacyllene comancheiRice and Morris andMegacyllene angulifera (Casey) (Coleoptera: Cerambycidae), The Coleopterists Bulletin 67 (2), pp. 89-93 : 89-93

SYNONYMY OF MEGACYLLENE COMANCHEI RICE AND MORRIS AND MEGACYLLENE ANGULIFERA (CASEY) ( COLEOPTERA : CERAMBYCIDAE )

CHARLES J. HART AND MICHAEL A. IVIE Montana Entomology Collection 1911 West Lincoln Street Montana State University Bozeman, MT 59717, U.S.A. [e-mail]; [e-mail]

Megacyllene angulifera (Casey, 1912) and Megacyllene comanchei Rice and Morris, 1992 are rarely collected Great Plains species (Linsley 1964; McNamara 1991; Yanega 1996; Heffern 1998; Rice and Morris 1992; MacRae 2008). Megacyllene angulifera is mostly known from the northern Great Plains states and provinces south to Kansas (Linsley 1964; McNamara 1991; Yanega 1996; Blodgett et al. 2005). Megacyllene comanchei is almost exclusively known from the type locality at White River Lake in Crosby County, Texas (Rice and Morris 1992; MacRae and Rice 2007; MacRae 2008), with a few recent reports north to Kansas and South Dakota (MacRae and Rice 2007; MacRae 2008).

The major distinguishing characters of M. comanchei and M. angulifera given by Rice and Morris (1992) are the distribution of white and yellow pubescence on the dorsal surface and the degree of coalescence of the preapical and apical bands. In M. comanchei , the strongly angulate premedian band and the sutural segments of the postmedian band are white with the rest of the elytral pubescence yellow and the preapical and apical bands joined laterally and along the suture. However, specimens identified as M. angulifera by Yanega (1996, fig. 108a-b) include one with white bands and another with coalesced bands. Reared specimens reported from Montana ( Blodgett et al. 2005) include individuals as described for M. angulifera , and some intermediate between the two. The holotype of M. angulifera was found to exhibit intermediate characters ( Fig. 1 ), and paratypes of M. comanchei were found to include the entire range of color variation. A specimen clearly belonging to M. comanchei from Billings, Montana put the known range of the species hundreds of kilometers farther northwest and precipitated this study.

In order to evaluate the specific status of these two names, we assembled a large collection of these rare beetles. The 84 specimens examined directly (n = 76, see below) or in photographs (n = 8: Yanega 1996; Bezark 2013; Lingafelter et al. 2013) can be sorted into three morphs: an M. angulifera auctorum Form with unicolorous yellow or ashy bands; an Intermediate Form with a mixture of yellow and white in the premedian and postmedian bands as well as on the base of the pronotum and elytra; and an M. comanchei Form with those bands completely white ( Figs. 2 – 3 ). These were then evaluated by sex, season, geography, and size.

Of the 84 specimens examined, 26 are the M. angulifera Form, 20 fit the Intermediate Form, and 38 are the M. comanchei Form. There is no clear geographic pattern to this variation as all three forms are found from Alberta to Texas ( Fig. 4 ), often being taken together in the same series on the same day. In all of the states and provinces except one (Oklahoma, n = 2), where more than one specimen was collected, a range of phenotypes were present. Furthermore, there was no correlation with sex or size of the beetle .

The variable elytral pubescence color and pattern is not unique to M. angulifera . Other species of Clytini , such as Megacyllene antennata (White, 1855) , Megacyllene decora (Olivier, 1795) , and Xylotrechus undulatus (Say, 1824) , exhibit individual variation in white to grey to yellow pubescence or narrow to coalesced bands (Linsley 1964). It is not surprising that M. angulifera would have variable elytral pubescence colors among individuals.

Host plant differences between M. comanchei and M. angulifera are not apparent. The only known larval association is for six M. angulifera adults reared from the roots of white prairieclover, Dalea candida Michx. ex Willd. (Fabaceae) ( Blodgett et al. 2005). Five of these reared individuals are the M. angulifera Form, and the other is an Intermediate Form ( Figs. 2b , 3b ). The known distribution of D. candida overlaps all the locations where M. comanchei and M. angulifera have been collected (USDA 2013). The larval host of the M. comanchei Form is unknown. However, with the exception of Megacyllene caryae (Gahan, 1908) , the larval hosts of members of Megacyllene Casey seem to be restricted to Fabaceae (Linsley 1964; Yanega 1996; Heffern 1998; Blodget et al. 2005; MacRae 2008).

Adults of what Yanega (1996) calls M. angulifera , which is a mixture of the Forms, have been found on Solidago L. ( Asteraceae ) which is a common adult host for other Megacyllene species (Linsley 1964; Yanega 1996; Heffern 1998). Adults of the type series of M. comanchei were found in association with dead crowns of an unidentified species of Heterotheca Cass. (Asteraceae) (Rice and Morris 1992), but this series is also a mixture of Forms. In Nebraska, three individuals of the M. angulifera Form and an individual of the Intermediate Form were found on D. candida , two individuals of the M. comanchei Form on Helianthus annuus L. ( Asteraceae ), and one individual of the Intermediate Form on Gutierrezia sarothrae (Pursh) Britton & Rusby (Asteraceae) . In Kansas, one specimen of the M. comanchei Form was found on Eriogonum effusum Nutt. (Polygonaceae) .

With any rarely collected species, understanding the full phenotypic variability is difficult with limited series. A few extreme individuals may differ greatly and at first blush may appear to be two separate species. However, with a larger assemblage of specimens over a wide geographic range, distinctions blur as a spectrum of intermediates are found. With the advantage of a larger series than was available to earlier workers, it now seems there is no evidence that M. comanchei and M. angulifera are separate species, and they are herein synonymized. This is summarized as:

Figures

Fig. 1. Holotype of Megacyllene angulifera (Courtesy of Larry Bezark and Steven Lingafelter).

Fig. 2. Premedian elytral bands of Megacyllene angulifera. Left column: M. comanchei Form, center column: Intermediate Form, right column: M. angulifera Form. Examples from a) Montana, Yellowstone County, Billings, b–c) Montana, Carbon County, Bridger, d) Nebraska, Keith County, Cedar Point Biological Station, e–f) Nebraska, Keith County, Lake McConaughy, g–h) Texas, Crosby County, White River Lake, i) Texas, Crosby County, White River Lake, paratype.

Fig. 3. Postmedian sutural segments of Megacyllene angulifera. Left column: M. comanchei Form, center column: Intermediate Form, right column: M. angulifera Form. Examples from a) Montana, Yellowstone County, Billings, b–c) Montana, Carbon County, Bridger, d) Nebraska, Keith County, Cedar Point Biological Station, e–f) Nebraska, Keith County, Lake McConaughy, g– h) Texas, Crosby County, White River Lake, i) Texas, Crosby County, White River Lake, paratype.

Fig. 4. Map with number of specimens examined per state or province and range of phenotypes. The single Megacyllene angulifera Form specimens from Indiana and Minnesota are not included on the map.