versión impresa ISSN 0065-1737
Acta Zool. Mex vol.25 no.1 Xalapa abr. 2009
First report of the exotic bruchid Specularius impressithorax (Pic) on seeds of Erythrina coralloides DC. in Mexico (Coleoptera: Bruchidae)
Primer reporte del brúquido exótico Specularius impressithorax (Pic) encontrado en semillas de Erythrina coralloides DC. en México (Coleoptera: Bruchidae)
Jesús ROMERO NÁPOLES1, J. M. KINGSOLVER2 & Cesáreo RODRÍGUEZHERNÁNDEZ1
1 Instituto de Fitosanidad, Colegio de Postgraduados, México. firstname.lastname@example.org
2 Florida State Collection of Arthropods, Florida Department of Agriculture & Consumer Services, Gainesville, Florida. USA
Se reporta por primera vez en México la presencia del brúquido exótico Specularius impressithorax (Pic), al cual se le encontró alimentándose de un nuevo hospedero, Erythrina coralloides DC. Se proporciona información sobre el grado de daño que provoca este insecto a las semillas de esta leguminosa.
Specularius is an Old World genus, according to Kingsolver & Decelle (1979) including nine species and two subspecies; however, the genus need to be reviewed in the future. The most important species in the genus is Specularius impressithorax (Pic) because of its wide distribution and that it feeds on various species of Erythrina. The other species of Specularius feed on other legumes, except Specularius ghesquierei Decelle that feeds on unidentified species of Erythrina.
The genus Erythrina is a flowering plant that is pantropic in distribution. In 1974, Krukoff & Barnaby revised the genus and recognized 105 species; latter in 1977, Gunn & Barnes described the seeds of 101 species. Neil (1988) studied the biosystematic relationships of the species and recognized 112 species. Barrera et al. (2002) mentioned that the Erythrina includes 117 species. Most of the them are used as ornamentals; however some species are used in South America as food, such as Erythrina edulis because its flowers are prepared in salads and sweets and its infusion taken for anxiety and urinary problems. In agroalimentary programs seeds are transformed into flour with high protein content.
In January 6, 2007 the third author collected seeds of E. coralloides DC. on the campus of Colegio de Postgraduados, Montecillo, Estado de Mexico. The coordinates of the site are 19°27'45.73"N and 98°54'13.03"W at 2256 m above sea level. After some days bruchids emerged from the seeds. For identification we followed the Kingsolver (1986) and Romero & Johnson (1999) technique for genitalia study. The genitalia were compared with specimens of S. impressithorax deposited in the Entomological Collection of Fitosanity Institute at Postgraduate College (CEAM). All material was pinned and labelled and stored at CEAM.
The bruchid species was identified as Specularius impressithorax (Pic), and constitutes the first report for this exotic species in Mexico. The analysis of 293 seeds showed that 169 (57.68%) were healthy, and 84 (28.67%) had seeds with eggs on them but without an operculum of emergence (OE). However, some of these were fertile (FE). This was easy to corroborate because after removing the egg the entrance hole that the larva made could be seen and dust could be seen inside of the egg, however none of these reached the adult stage. Translucent eggs were not fertile (NF), sometimes it was possible to see the small dead larva inside the egg (Fig. 1 A). The remaining 40 seeds (13.65%), showed one to nine glued eggs plus one to six OE (Fig. 1B) per seed (Table 1).
Johnson & Siemens (1995) and Johnson & Romero (2004) state that there are three guilds of bruchid oviposition on seeds: (Guild A) species that oviposit on fruits while on the plant; (Guild B) species that only oviposit on seeds exposed in fruits while still on the plant; and (Guild C) bruchids that only oviposit on seeds once they are exposed on the substrate. According to this guild classification system, S. impressithorax belongs to Guild B (Figs. 1C & D).
According to Romero & Johnson (2002) the only species of Specularius that feed on Erythrina are Specularius ghesquierei on Erythrina sp. (Democratic Republic of Congo) and the following host for the latter are: S. impressithorax. Erythrina abyssinica DC. (Sudafrica & Zimbabwe), E. abyssinica DC. subsp. abyssinica DC. (Tanzania), E. caffra Thunb., E. cristagalli L., E. humeana Sprengel (Rhodesia), E. latissima E. Mey., E. lysistemon Hutch., E. mildbraedii Harms (Nigeria), E. orophila Ghesq., E. pallida Britton, E. sandwicensis Degener (Hawaii), E. senegalensis DC. (Angola, Ghana, Nigeria), E. variegata L. (India). Therefore, Erythrina coralloides DC. is a new host record for this species.
At this moment, we do not know how widely S. impressithorax is distributed in Mexico. The only place where specimens have been collected is that mentioned above. It is possible that the introduction of the exotic bruchid was through infested seeds, perhaps in one of the Erythrina species from the Old World. Once relocated, this bruchid started feeding on E. coralloides that is a very abundant plant in many places of Mexico, USA and Central America.
We thank Dr. Stephen Koch from the Programa de Botanica, Colegio de Postgraduadaos, for the plant identification, and M.C. Jorge Valdéz Carrasco from Programa de Entomología y Acarología, Instituto de Fitosanidad, Colegio de Postgraduados for taking the photographs.
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