Amphelasma cavum Barber

Eben, Astrid, 2000, New host plant record forAmphelasma cavumBarber (Chrysomelidae: Galerucinae: Luperini), The Coleopterists Bulletin 54 (3), pp. 408-408 : 408

New host plant record for Amphelasma cavum Barber

( Chrysomelidae : Galerucinae: Luperini)

Lists of host plants of leaf beetles are often catalogues of captures with few exceptions where feeding on parts of the plant was actually observed. It has been estimated that only about 20% of the host plants for all described Chrysomelidae are known (P. Jolivet and T. J. Hawkeswood. 1995. Host­plants of Chrysomelidae of the World. Backhuys Publishers, Leiden, pp.281).

A number of Chrysomelid species in the section Diabroticites (Luperini) is characterized by a strong kairomonal response to cucurbitacin­producing Cucurbita spp. (Cucurbitaceae) (R. L. Metcalf. 1986. Journal of Chemical Ecology 12:1109–1124; A. Eben, M. E. Barbercheck and M. Aluja. 1997. Entomologia experimentalis et applicata 82:53– 62). These extremely bitter terpenoid compounds serve as arrestants and feeding stimulants for Diabroticites. Amphelasma cavum Barber has been placed into the section Diabroticites (J. A. Wilcox. 1972. Coleopterorum Catalogus. Supplementa. Pars 78, Fasc. 2, Chrysomelidae : Galerucinae, Luperini: Aulacophorina , Diabroticina . Uitgeverij Dr. W. Junk, ̍s­Gravenhage). The neotype was collected in Cordoba , Veracruz, Mexico, and is deposited in the Frey Collection ( Museum of Natural History , Basilea , Switzerland). The only host plant record to date, reported A. cavum on Prosopis (Mimosaceae) in Mexico (C. R. Ward, C. W. O̍ Brien, L. B. O ̍ Brien, D. E. Forster and E. W. Huddleston. 1977. Annotated Checklist of New World Insects associated with Prosopis (Mesquite) . USDA Technical Bulletin No. 1557:1–115). Nothing is known about its feeding preferences.

This summer, I repeatedly observed A. cavum adults feeding on Salvia xalapensis Benth. (Labiatae) growing in close vicinity with Cucurbita martinezii Bailey , a wild, cucurbitacin­producing species. In order to determine if S. xalapensis or C. martinezii are host plants for A. cavum , beetles (n = 12) were offered newly expanded, equally sized leaves from S. xalapensis and C. martinezii in a choice test. Beetles were placed individually in a petri dish with one leaf of each of the two plants. After 36 h the amount eaten from each leaf was measured with a leaf area meter (LI 3100, Licor Inc., Nebraska). None of the beetles tested in the leaf choice assay fed from bitter C. martinezii leaves, but all ate substantial amounts of S. xalapensis leaves (% leaf area eaten: 59.5 ± 13.06; mean ± SEM).

The results indicate, that S. xalapensis , from which the beetles were collected, is actually a host plant for A. cavum adults. Cucurbita martinezii was not accepted as host, contrary to results from bioassays with 18 other Mexican Diabroticite species (A. Eben, M. E. Barbercheck and M. Aluja. 1997, loc cit.; Eben, unpubl. data). Interestingly, cucurbitacins in leaves did not serve as kairomones for A. cavum .

This report adds one more species to the published host plant records for neotropical Galerucinae. It remains to be tested, if Prosopis spp. are also host plants for A. cavum . This species might feed on several different plant families, but does not show the pharmacophagous feeding on bitter cucurbits, typically observed in other Diabroticites. Voucher specimen of S. xalapensis and A. cavum were deposited in the herbarium and in the insect collection of the Instituto de Ecología, A.C.

Thanks to S. Avendaño Reyes (Instituto de Ecología, A.C.) for the identification of S. xalapensis . The help of M. Brancucci and E. Sprecher (Museum of Natural History, Basilea) during my work in the Frey Collection is greatly acknowledged. I appreciate the constant support of A. Espinosa de los Monteros with the collection of beetles.