Coleoptera: Chrysomelidae) in America North of Mexico
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Great Basin Naturalist Volume 43 Number 4 Article 10 10-31-1983 A revision of the genus Microrhopala (Coleoptera: Chrysomelidae) in America north of Mexico Shawn M. Clark Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Clark, Shawn M. (1983) "A revision of the genus Microrhopala (Coleoptera: Chrysomelidae) in America north of Mexico," Great Basin Naturalist: Vol. 43 : No. 4 , Article 10. Available at: https://scholarsarchive.byu.edu/gbn/vol43/iss4/10 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. A REVISION OF THE GENUS MICRORHOPALA (COLEOPTERA: CHRYSOMELIDAE) IN AMERICA NORTH OF MEXICO Shawn M. Clark' .Abstract. — The eight known North American species of Microrhopala infest Solidagu, Aster, and other compos- itaceoiis plants. Descriptions and keys to species and subspecies are given. Microrhopala rileyi is named as a new .spe- cies from Missouri, A/, hecate (Newman) is removed from synonymy with M. cijanea (Say), and M. cijanea is reduced to a subspecies of M. excavata (Olivier). Lectotypes are designated for taxa described originally in the genus Hispa, i.e., Hispa vittata, H. xerene, and H. erebiis, and neotypes are designated for H. excavata and H. cijanea. Phylogenet- ic relationships are discussed. History.— The generic name Microrhopala (1865). Horn (1883) presented M. vulnerata was first published by Dejean (1837) and at- as a distinct species, but this was reduced to a tributed to Chevrolat. This name has often variety of rubrolineata by Weise (1911). Fi- been hsted with Dejean as its author, because *nally, M. rubrolineata var. militaris was it was never actually described or listed by named by Van Dyke (1925). Most of these va- Chevrolat. However, following the no- rieties represent true subspecies, but laetula menclatural interpretation of Barber and and interrupta are no longer recognized Bridwell (1940), authorship is again credited (Weise 1911, McCauley 1938). to Chevrolat in this study. Included in the Also, H. hecate Newman, 1841, was synon- genus were two valid species, Hispa vittata ymized with M. cyanea by Gemminger and Fabricius, 1798, and H. excavata Olivier, Harold (1876), and M. bivitticollis was de- 1808. scribed by Baly (1864) and later synonymized Melsheimer (1853) added H. cyanea Say, with M. rubrolineata var. signaticollis by 1823, to the genus but referred H. excavata Weise (1911). back to Hispa. Baly (1864) published the first In addition to the above species that ac- generic description of Microrhopala and des- tually belong to Microrhopala, various others ignated H. vittata as the type species. He also have sometimes been assigned to the genus returned H. excavata to the genus and added but do not belong here. These are M. porcata H. xerene Newman, 1838. Odontota rubro- (Melsheimer, 1846) (now in Glyphuroplata), lineata Mannerheim, 1843, was transferred to M. collaris (Say, 1823) (now in Chalepus and the genus by Crotch (1873), and, finally, synonymized with C. walshi), M. melsheimeri Schwarz (1878) named M. floridana and also Crotch, 1873 (now in Brachycoryna and syn- transferred H. erebus Newman, 1841, to the onymized with B. hardyi), M. plicatula (Fab- genus. Several other species are known from ricius, 1801) (now in Octotoma), M. uniformis tropical America but do not extend north of Smith, 1885 (now in Uroplata), M. dimidiata Mexico; no Old World species are known. Horn, 1883 (now in Pentispa and synony- In addition to the species cited above, sev- mized with P. melanura), M. montana Horn, eral varieties and geographical races have 1883 (now in Brachycoryna), M. suturalis been named in Microrhopala. LeConte (Baly, 1885) (now in Pentispa), and M. arizo- (1859a) presented M. signaticollis as a distinct nica Schaeffer, 1906 (now in Pentispa and species, but it was reduced to a variety of synonymized with P. suturalis). rubrolineata by Crotch (1873). Microrhopala Relationship to Other Genera.— With- xerene var. interrupta was named by Couper in the family Chrysomelidae, Microrhopala is 'Department of Zoology, Brigham Young University, Provo, Utah 84602. Present address: Department of Entomology, Ohio State University, Columbus, Ohio 43210. 597 598 Great Basin Naturalist Vol. 43, No. 4 placed in the subfamily Hispinae and the back on each other. After oviposition, the fe- tribe Uroplatini (Weise 1910). The tribe male covers the eggs with an anal secretion, Uroplatini is best characterized by having the likely feces, that soon hardens to a black, four terminal segments of the antenna very crusty material, which probably serves to closely united and often appearing as a single protect the eggs. Often, several rows of eggs segment. are laid alongside one another, in which case In addition to Microrhopala, five other all rows are protected by a single covering. I of genera are included in this tribe. Four observed a female of M. vittata laying eggs Brachycoryna, these genera.— Octotoma, on 16 June 1981; these eggs hatched on 10 Stenopodius, and Glyphuroplata—Sire easily July 1981, thus indicating a period of 3.5 distinguished from Microrhopala as follows. weeks (25 days) in this stage of development. Brachycoryna and Stenopodius are distin- When the eggs hatch, the larvae enter di- guished from the others by their short an- rectly into the leaves below the crusty cov- tennae that are not longer than the pro- ering without exposing themselves to the ex- notum, and Octotoma and Glyphuroplata are ternal environment and begin feeding on distinguished by having more than eight tissues between the upper and lower epider- striae on the elytra. Apart from being mem- mal layers. Mining begins near the apex of bers of the same tribe, these genera show no the leaf and continues to the base. I have particularly close affinities to Microrhopala. seen larvae of xerene emerge from one However, the fifth genus, Pentispa, shares M. leaf enter another, where mining activity many characters with Microrhopala and is ap- and Eventually, the larvae dispersed parently closely related. It is distinguished by continued. the flattened, more strongly costate elytra, themselves such that only one to four larvae but even this character does not eliminate all were usually found in each leaf. In 1981 I difficulties in separating the genera. In fact, a noted that the first eggs of M. vittata hatched careful study of the species of Pentispa may on 23 June, and pupae were first noted on 22 eventually indicate that they are congeneric. July, thus indicating a larval duration of ap- proximately one month (30 days). At the end of the larval stage many leaves Biology contain large, inflated cavities where the lar- vae have mined. The beetles pupate in these The life cycle and development of Micro- cavities. According to my observations, the rhopala are well known for only M. vittata pupal period lasts for five to eight days. and M. xerene (Hendrickson 1930, McCauley The adults emerge and spend several days 1938). During the summers of 1980 and 1981, within the mines until their cuticle is suffi- I observed these two species in Provo Can- ciently hardened. They then abandon the yon, Utah, and confirmed previous reports mines and begin to feed externally on the about them, but also uncovered new informa- same host as did the larvae. Small areas of tion. These data summarize what is known the leaf, usually not much larger than the size about vittata and xerene, but much of it prob- of a beetle, are skeletonized by this activity. ably applies to the other species in this genus. After feeding, a few beetles mate. However, So far as is known, larvae of all species in activity is delayed until the next the genus are internal leaf miners of compos- most mating itaceous plants, and adults are external leaf spring. beetles feeders of the same host species. Host selec- Toward the end of the summer, the in search of tion is very narrow, and each beetle species is begin to wander, presumably this time restricted in its feeding activity to only a few places to pass the winter. During plant species. they may be found on many plant species, Oviposition occurs in the early summer but they do not feed on them, and this has and may be either on the upper or lower sur- likely led to several erroneous host plant rec- face of the host leaf, usually near the apex. A ords. Eventually, the beetles find areas under female usually lays three to five disk-shaped loose bark, crevices in the soil, accumulated eggs in a contiguous row. The eggs are posi- debris, or leaf litter, and pass the winter in tioned on their edges and are slightly tilted these situations. October 1983 Clark: Revision of Microrhopala 599 When spring arrives, the beetles emerge Douglass 1929, McCauley 1938). These in- from their overwintering sites, then resume clude the presence or absence of costae on feeding and mating activity. Males remain the elytra, the size of serrations on interstriae mounted atop females for several hours be- 9, the size and depth of pronotal and elytral fore copulation actually takes place. I have punctures, the color, the presence or absence observed such pairs of M. vittata rapidly of metallic lusters, and the size and con- swaying from side to side in repeated motions formation of colored markings when present. that continue for up to one minute. The mo- McCauley (1938) attempted to find re- tions may be important in identifying a mate, liable genitalic characters but reported the and it is possible that comparable activities following: may exist for other species.