StridulAtory Sound emiSSion of Panstrongylus rufotuberculatus ChAmpion , 1899 , ( hemipterA : reduviidAe : triAtominAe )

this study contains the first report of stridulatory sound observed in Panstrongylus rufotuberculatus Champion, 1899, and also a new record of this species in venezuela. the conditions in which stridulation occurred are described, as well as the general environmental characteristics of the localities where it was found. this triatomine only performs the sound in conditions of extreme provocation.


InTROdUCTIOn
Stridulation occurs widely in heteroptera, involving many different parts of the body and varying with the species (Chapman, 1998). in reduviidae, (hemiptera) the stridulatory system consists of a file of sulcus in the prosternum, with the tip of the rostrum forming the scraper.Stridulatory sulcus, the general shape, pilosity, the cuticular structure and the edges, as well as certain characteristics of the parallel groves, can be used for taxonomic purposes (Carcavallo et al., 1998).it has been suggested that sound emission in insects plays a role in gender identification during copulation (Chapman, 1998). in the case of triatominae, it has been established that such emissions are part of the intraspecific communication mechanisms (Schofield, 1977); for example, females that are nonreceptive to T. infestans Klug, 1834 or R. prolixus Stal, 1859 use sound to reject males (manrique & lazzari, 1994;manrique & Schilman, 2000).the stridulation may act as a mechanism for repelling potential predators (leston, 1957), defensive behaviour or recognition between sex, for example in R. prolixus can indicated female reject males or defensive.the meaning keeps a relationship with the intensity and frequency of stridulatory sound, and this with inter-ridge distances on stridulatory grooves (manrique & Schilman, 2000;Schilman et al., 2001).
the present study is the first record of audible sound in Panstrongylus rufotuberculatus Champion, 1899.

MATERIAlS And METHOdS
during the capture of Panstrongylus geniculatus latreille, 1811 in el hatillo, miranda State (reyes-lugo et al., 2001), a male specimen of Panstrongylus rufotuberculatus Champion, 1899 was obtained at 22 h on may 04, 2001 near a light outside one of the buildings at the study site, and was kept alive in the laboratory for several days.A second male, which had been collected in the same way in San diego de los Altos in may 1999 and preserved since then in 70% etanol, has been included in this study.identification of the specimens was carried out using the triatominae keys ramiréz-pérez (1985) and Carcavallo et al. (1998).morphological studies of the stridulatory organ of both samples were realized with a hitachi S-450 scanning electron microscopy. in addition the material was protected from breakage by using low acceleration (25 Kv).

RESUlTS
When the live specimen of P. rufotuberculatus was held with a pincer by the thorax in a ventral position in order to extract a sample of faeces with a view to detecting the presence of Trypanosoma cruzi, the insect emitted a sound similar to that produced by sandpaper scraping wood.part of the stridulatory organ can be seen in a photograph obtained with the scanning electron microscopy at 100x (fig. 1) dISCUSSIOn it could be confirmed that the stridulatory emission by P. rufotuberculatus was produced by a similar vibration to that described for T. infestans Klug, 1834 (Schofield, 1979), in other words by rubbing the tip of the reflexed proboscis along the transversely ridged prosternal groove with an anterior-posterior movement; the return stroke, posterior-anterior, is silent (Schofield, 1977).this vibratory movement was only observed when the sample was held with the pincer in the abovementioned position, and it only lasted about five minutes, although the insect remained immobile for a longer period.in the silence of the laboratory, the stridulation was audible up to about one meter away.the sound emitted by P. rufotuberculatus in the laboratory only when held with a pincer in a ventral position, matches that reported in the case of other triatominae when submitted to conditions of extreme provocation such as the attack of a predator (e.g., leston, 1957;Schofield, 1979).
P. rufotuberculaus is found in Argentina, Bolivia, Brazil, Colombia, Costa rica, ecuador, mexico, panama, peru and venezuela (Schofield, 1994, Salomón et al., 1999). in the municipality of Amalfi in Antioquia, Colombia, P. rufotuberculatus is considered a high epidemiological risk for the transmission of Trypanosoma cruzi and represents 47% of captured triatomine, constituting the second most common reduvid caught inside buildings (Wolf et al., 2001).likewise this triatomine has been reported in domestic environments in peru, Bolivia and south of ecuador (Abad-franch et al., 2001).Adults of this species are attracted by lights on walls outside houses (Salomón et al., 1999;Abad-franch et al., 2001). in Costa rica P. rufotuberculatus can be found from sea level to 1,450 m, but seems to be more common at levels below 800 m (74.1%) and especially below 200 m (52.5% of the specimens); it tends to be more common during the first six months of the year (dry season and beginning of the rainy season) (zeledón et al., 2001).
in Bolivia four nymphs and one adult of P. rufotuberculatus were found colonizing a house located in a forest environment; it has also been found in Bolivia at altitudes that range between 1,500 to 2,600 m (noireau et al., 1994).this species has been found associated with wild mammals (kinkajous, bats and opossums) and adult specimens have been observed occasionally in human dwellings in ecuador, peru and Bolivia (zeledón et al., 2001).
in venezuela, P. rufotuberculatus has rarely been collected although it has been reported throughout most of the country, namely in the states of Aragua, Carabobo, Cojedes, distrito federal, falcón, guarico, lara, monagas, portuguesa, Sucre, tachira, trujillo, yaracuy, zulia, territorio delta Amacuro and territorio Amazonas (lent & pifano, 1940, Cova-garcía & Suarez, 1959, ramírez-pérez, 1985).the findings in el hatillo and San diego de los Altos are the first record of this species in miranda State.Both places are about 25 km from Caracas, the former to the Southwest and the latter to the Southeast of the capital, and are located in the same region where Panstrongylus geniculatus latreille, 1811 was first discovered to be colonizing domestic environments (reyes-lugo & rodríguez-Acosta, 2000).
At the present the biological and p. C. r. analysis characterization of trypanosome isolated from the faeces of P. rufotuberculatus corresponds to T. cruzi (díaz-Bello et al., 2002).these results are relevant because in venezuela many aspects of the biology, ecology and behavior of this triatomine remain unknown.