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Neotrop. entomol. vol.38 no.4 Londrina July/Aug. 2009
SYSTEMATICS, MORPHOLOGY AND PHYSIOLOGY
A new species of Acanthoscelides Schilsky (Coleoptera: Bruchidae) from Mexico with some biological notes
Nueva especie de Acanthoscelides Schilsky mexicana (Coleoptera: Bruchidae) con algunas notas biologicas
Jesús Romero NápolesI; John M KingsolverII
IColegio de Posgraduados, Campus Montecillo, km 36.5 Carretera México-Texcoco Montecillo Edo. de México, C. postal 56230, México; firstname.lastname@example.org
IIFlorida State Collection of Arthropods, Florida Department of Agriculture & Consumer Services, Gainesville, Florida; Bruchid@aol.com
A new species of Acanthoscelides collected in Chiapas, Mexico is described and figured. Rhynchosia precatoria is cited as a new host plant record for A. dani sp.n and A. flavescens Fahraeus. The braconid Heterospilus prosopidis Viereck was found as parasitoid of both species of bruchids.
Key words: Seed beetle, taxonomy, Neotropical region, morphology, Acanthoscelidini
Se describe e ilustra una nueva especie de Acanthoscelides colectada en Chiapas, México. Se cita a Rhynchosia precatoria como una nueva planta hospedera para A. dani sp.n y A. flavescens (Fahraeus). Al bracónido Heterospilus prosopidis Viereck se le encontró parasitando a ambas especies de brúquidos.
Palabras clave: Gorgojo de la semilla, taxonomía, región Neotropical, morfología, Acanthoscelidini
Acanthoscelides Schilsky is the largest genus of Bruchidae of the New World containing about 340 species, however there are more than 200 species remaining to be described (Johnson 1990). A checklist published in 2004 states that in Mexico there are 119 species of Acanthoscelides, representing 35% of the species recorded for this endemic genus of the New World (Romero & Johnson 2004a).
According to Johnson (1990) Acanthoscelides is characterized by following combination of characters: antenna short to long, sexually dimorphic or not; pronotum conical, campaniform; elytra about twice as long as broad, striae moderately to deeply impressed; hind femur usually expanded medially to about width of or wider than width of hind coxa, armed with large subapical acuminate spine followed by none to four smaller spines, mucro 0.05-1.0 times as long as tarsomere 1; abdomen usually with sterna unmodified, pygidium ranging from evenly rounded to strongly convex, apical margin of last sternum slightly to strongly emarginate to receive apex of pygidium, apical margin of last sternum of female usually without emargination; male genitalia usually without dorsal hood at apex, armature of internal sac ranging from only a lining of spicules to large spines; lateral lobes cleft for a part of their length.
However Johnson (1990) recognized that the genus often is used as a genus into which species are placed that do not fit within the limits of other genera. In order to partly solve this problem Johnson and Romero (2006) created a new genus, Neobruchidius, transferring to it seven Acanthoscelides with metafemur armed with one large subapical acuminate spine, with no additional smaller spines. So the character quoted by Johnson (1990) to describe Acanthoscelides "metafemur armed with large subapical acuminate spine followed by none to four smaller spines" should be changed to "metafemur armed with large subapical acuminate spine followed by two to four smaller spines".
The last species of Acanthoscelides decribed from Mexico was in 1990 by Johnson in his work "Systematics of the Seed Beetle genus Acanthoscelides (Bruchidae) of Northern South America". After 17 years a new species of this genus from Mexico is here described including a new host plant record.
Material and Methods
Methods adopted in this paper to prepare genitalia were those of Kingsolver (1970) and Kingsolver and Whitehead (1974); for interpretation of genitalia of Romero and Johnson (1999), and for terminology and taxonomic characters of Johnson (1983, 1990).
Male. Measurements. Length (pronotum-elytra) 2.38 mm; width 1.70 mm; maximum thoracic depth 1.35 mm.
Integument color. Body dark except, base of vertex, antennal segments 1 to 4 and 11 red orange; legs red orange to dark brown.
Vestiture. Pronotum, elytra, and pygidium with variegated pubescence of white, pale and black tufts of hairs, rest of the body with mixed white and pale pubesence; base of metepisternum, and lateral areas of ventral segments 2 to 5 with a white spot (Figs 1a,b).
Structure. Head short and broad, densely micropunctulate; frons with median carina; distance between eyes about 0.60 as wide as eye width; eye cleft 0.63 its length by ocular sinus; posterior margin of eye protruding from adjacent surfaces; postocular lobe rounded; distance from base of antennae to apex of labrum about half as long as distance from upper limits of eyes to apex of labrum; antennal segment one filiform, 2, 3 moniliform to filiform, 4 subserrate, 5 to 10 serrate, 11th subacute apically; antenna extending to humerus or slightly beyond. Disk prothorax campanulate; punctulate with many scattered coarse punctures; cervical sulcus moderately deep, extending from near coxal cavity to about 0.75 distance to pronotal midline; lateral prothoracic carina extending from base to 0.35 distance to coxal cavity; without short median impressed line on median basal lobe; prosternum separating procoxae for about 0.7 their length. Scutellum black, moderate in size, bifurcate at posterior margin, clothed with moderately dense white and pale hairs to give quadrate appearance; elytron about twice as long as broad; striae deep, punctate, strial intervals punctulate; distance between striae at base subequal; humerus punctulate, glabrous, shiny black; undersurfaces and all of hind coxa punctulate, metepisternum coarsely foveolate; hind femur constricted basally and apically, expanded medially to about width of coxa, ventral surface with carina subserrate on inner margin; femur armed with subapical acuminate spine about 1.18 times as long as width of tibial base and two acuminate spines about 0.4 as long as first spine; hind tibia with dorsomesal, lateral, lateroventral, and ventral glabrous longitudinal carinae; dorsal surface of tibia without fossa; tibial corona with four spinules, mucro 0.28 as long as first tarsomere; without sinus at base of spine; first tarsomere with ventral and lateral glabrous longitudinal carina, usually lacking mesal carinae. First visible abdominal sternum slightly flattened medially, posterior margin straight, longer than remaining sterna; sterna 2 to 4 similar in size; fifth emarginate; pygidium punctate with scattered foveolae, convex in lateral view.
Genitalia. Median lobe moderate in length; in ventral view, ventral valve rounded, lateral margins lightly convex; armature of internal sac with apical line of spines, a mesal couple of angulate spines, below of these a pair of spinescent sclerites with scattered spinules, three pairs of spines with different shape, and sometimes a unpaired small spine, and a basal sclerite clothed with spines (Fig 2a). Lateral lobes elongate expanded at apex, cleft to about 0.28 their length (Fig 2b).
Female. Similar to male. Length (pronotum-elytra) 2.48 mm; width 1.77 mm; maximum thoracic depth 1.43 mm.
Type series. Holotype male, allotype and one paratype: MEXICO, Chiapas, km 40 carr. fed. Estacion La Chontalpa - Romulo Calzada, 17º23'03.7'' N; 93º32'48.4'' W , 21/IV/2007, J Romero Nápoles collector; in Rhynchosia precatoria seeds, JRN # 446/2007. Holotype deposited at National Museum of Natural History (USNM), Washington, allotype at Florida State Collection of Arthropods (FSCA), Gainesville and paratype at Colección Entomologica del Instituto de Fitosanidad (CEAM), Mexico.
Distribution. Mexico (Chiapas).
Host Plant. Rhynchosia precatoria (Humb. & Bonpl. Ex Willd.) DC. (Fig 3).
Etymology. The specific epithet refers to the second name of Clarence Dan Johnson, one of the most brilliant bruquidologists, who spent all his life working with taxonomy of the family and determining the relationships with host plants.
Remarks. Acanthoscelides dani n.sp. belongs to group flavescens of Acanthoscelides (Johnson 1983, 1990, Johnson & Romero 2006) which include 13 species (alboscutellatus, baboquivari, burkei, campeche, compressicornis, distinguendus, flavescens, hectori, isla, manleyi, soijae, zeteki). All of them share the mucro 0.25 to 0.4 as long as the first hind tarsomere, rounded or almost rounded apex of the ventral valve of the male genitalia, and elytral pubescence variegated. The nearest species to A. dani n.sp. is A. hectori Kingsolver, 1980 where the external morphology is very similar, however the sclerites in the internal sac of male genitalia are very different considering the shape and number of sclerites in the internal sac.
Of those Acanthoscelides whose hosts are known, all feed in papilionid legumes (except for the North American species A. alboscutellatus (Horn), 1873, which feeds on Onagraceae, and A. compressicornis (Schaeffer), 1907, which feeds in mimosoid and caesalpinoid legumes).
Rhynchosia is a large and diverse genus of Malvaceae plants, consisting of nearly 200 species; there are 52 species in the New World (Grear 1978).
It is distributed in warm temperate and tropical regions of both eastern and western hemisphere. R. precatoria is recorded from Mexico to Colombia. Its seeds are used as a traditional medicine to cure some aches; some people also use the seeds to make necklaces and bracelets.
In the Old World there are four species of bruchids of two genera that feed on Rynchosia seeds, Specularius bridwelli Arora (Rhynchosia minima (L.) DC.), Specularius ruber (Pic) (Rhynchosia albae-pauli Berhaut), Specularius erythraeus (Pic) (Rhynchosia densiflora (Roth) DC., Rhynchosia buettneri (Harms), and Borowiecius varicolor (Boheman) (Rhynchosia sp.) (Udayagiri & Wadhi 1989, Anton 1999). In the New World the following genera have Rhynchosia seeds as hosts: Acanthoscelides (15 species on 16 host plants), Caryedes Hummel (3:1), Meibomeus Bridwell (1:1), and Zabrotes Horn (1:1) (Romero & Johnson 2004b); so in 19 species of Rhynchosia there are a total of 24 species in six genera of Bruchid recorded.
Biological notes. From a sample of 158 dehiscent pods with 220 seeds 210 were healthy and 10 were damaged by bruchids. Of those with damage, five bruchids emerged from five seeds (one specimen per seed), two specimens of Acanthoscelides flavescens (Fahraeus) and three of the new species A. dani . n.sp. From the other five seeds emerged parasitoids. We did not see any glued egg on seeds or pods, just as bruchids commonly do, so we assumed that bruchids oviposit like A. obtectus (Say) just scattering eggs on pods and seeds, then larvae walk until they find a seed.
A. flavescens is a polyphagous bruchid, feeding on three species of Rhynchosia (R. longeracemosa, R. minima, R. phaseoloides, however "it may feed on other 10 more genera of Malvaceae, Polygonaceae and Leguminosae (Abutilon, Acacia, Aeschynomene, Coccoloba, Crotalaria, Eriosema, Galactia, Tephrosia, Vicia, Vigna) (Johnson 1989, Romero & Johnson 2004b). Rhynchosia precatoria constitutes a new host record for A. flavescens. From the five seeds of R. precatoria emerged five Heterospilus prosopidis Viereck (Braconidae) (one specimen per seed). This braconid was recorded as a parasite of A. flavescens in Rhynchosia minima (Hetz & Johnson 1988). Probably H. prosopidis may feed on any of either species of bruchids A. flavescens or A. dani n.sp., because the two later are infesting seeds of R. precatoria.
The first author thanks Margaret Johnson the friendship and will of all materials and literature that C D Johnson used in his bruchid work, including a magnificent synoptic bruchid collection.
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Edited by Roberto A Zucchi - ESALQ/USP