A key to the Mexican and Central America Genera of Anthonomini (Curculionidae, Curculioninae)

Abstract Presently the only keys available for identification of genera of Anthonomini are limited to those of the United States of America and Canada. A dichotomous key is presented to identify all genera of Mexican and Central American Anthonomini. Previous keys do not include the genera Achia, Botanebius, Loncophorus, Loncophorellus and Melexerus. A brief synopsis is given for each genus and photographs of representative species are included.


Introduction
The family Curculionidae of Mexico and Central America is rich in species (Anderson and O'Brien 1996). Although general keys to the subfamilies of Curculionidae are available (Morrone 2000, Anderson 2002, Marvaldi and Lanteri 2005, the absence of regional keys to genera limit the study of Curculionidae in Mexico and Central America (Anderson and O'Brien 1996). Identification of some genera of weevils is possible through the use of the Biologia Centrali-Americana (Sharp and Champion 1911, Champion 1903, 1910 and by using keys for the United States of America and Canada (Kissinger 1964, Anderson 2002; however, material in the Biologia Centrali-Americana is notably outdated, keys are not always presented, and the North American keys do not include a significant portion of the Mexico and Central American genera, moreover, the taxonomic status of some genera has changed and new genera have been described and recorded for the region. Anthonomini is a tribe within the subfamily Curculioninae of the Curculionidae (sensu Alonso-Zarazaga and Lyal 1999). The tribe is one of the most diverse and complex of the family containing more than 800 described species within 43 genera, 24 of which are from the New World and 17 of these from México and Central America (Alonso-Zarazaga and Lyal 1999). The following characters will aid in placing species in this tribe collected in Mexico and Central America: rostrum free, not received into ventral channel, more or less cylindrical in cross section , longer than pronotum; antenna with scape not or just reaching the anterior margin of the eye; eyes nearly round; pronotum wider than long, narrowed in front, lacking postocular lobes (Figs 31-32); mesepimeron not ascended and not visible in dorsal view; elytral variable, generally wider at the base than the pronotum (Figs 27 and 29), striae punctured; pygidium covered by elytra; anterior coxae more or less equidistant from anterior and posterior margins of prosternum; sutures of abdominal ventrites straight and deep, except the first, which is less deeply impressed; tibia with a tooth at apex, usually larger on pro-and mesotibia; tarsi with claws free at base and with basal process or tooth (simple in Epimechus and Brachyogmus (Fig. 1)) (Dietz 1891, Kissinger 1964, Burke 1976and Anderson 2002. Several species of Anthonomini are superficially similar to Smicronyx (Smicronychini), Phyllotrox (Derelomini) or Tychius (Tychiini). These taxa can be distinguished from Anthonomini by the following combination of characters: Smicronyx have claws connate at base and pronotum with postocular lobes. Phyllotrox, femur with ventral margin simple, lacking tooth; procoxae closer to posterior margin than to anterior margin of prosternum. Tychius, suture between ventrites 2 and 3 markedly extended posterolaterally, reaching or passing suture between ventrites 3 and 4 (Tanner 1966 andKissinger 1964).
The host plants or plant associates of Anthonomini represent more than 35 families, including many species of agricultural importance. Two of the best-known pest species are the cotton boll weevil Anthonomus grandis Boheman and the pepper weevil Anthonomus eugenii Cano; Anthonomus grandis is a widespread and well-known pest of cotton. Anthonomus eugenii is widely distributed in the Southeastern United States, Hawaii, Mexico, Central America and the Caribbean. It feeds and develops in several species of Solanaceae but is better known as a pest of peppers, Capsicum spp. (Clark and Burke 1996). Other pest anthonomine include: Anthonomus signatus (strawberry weevil), A. nigrinus (potato weevil), A. musculus (cranberry weevil), A. pomorum (apple blossom weevil) A. pyri (pear weevil), A. fulvipes (cherry weevil), A. quadrigibbus (apple curculio), and Pseudanthonomus validus (currant fruit weevil), (Ahmad and Burke 1972, Burke 1976, Clark and Burke 1996, Clark 1987band Muñiz 2001.
The objective of the key presented here is to allow identification of genera of this tribe in Mexico and Central America.
Images of specimens of each genus were captured with the aid of a stereoscopic microscope and digital camera and processed using COMBINEZP software (Hadley 2010). PHOTOSHOP CS3® or CORELDRAW® software programs were used to highlight or draw characters cited in the key. A synopsis of each genus is provided giving: generic name, author and recorded year, total species for New World, number of species occurring in Mexico and Central America, distributions, family placement of associated plants, and bibliographic references to identify species.

Discussion
The tribe Anthonomini (sensu Alonso-Zarazaga and Lyal 1999) was reviewed and delimited by Burke (1976) who considered the systematics of the taxon to be in a "chaotic" state at the tribal and lower levels. From 1976 to the present, Horace R. Burke and Wayne E. Clark have conducted revisionary taxonomic studies on many of the New World genera and species. These taxonomic publications have greatly advanced the systematics of Anthonomini for the region, although much still remains to be resolved within the tribe, especially within the genus Anthonomus as there are currently no keys to the various species groups recognized in the studies of Clark. The key presented here allows for the identification of the genera of the tribe reported from Mexico and Central America. Some genera can easily be either recognized by characters or combinations of characters, such as: Brachyogmus, Magdalinops, Narberdia, Smicraulax and Huaca; however, the intergeneric relationships of several of the species of Anthonomus, Atractomerus, Loncophorus and Lonchophorellus are not so clearly delimited and may be harder to separate.