Unusual Calling Behavior of Anastrepha robusta Flies (Diptera: Tephritidae) in Nature

Abstract

Male calling behavior in Anastrepha (Schiner) fruit flies has been described in the following species: bistrigata (Bezzi), fraterculus (Wiedemann), ludens (Loew), obliqua (Macquart), pseudoparallela (Loew), serpentina (Wiedemann), sororcula (Zucchi), striata (Schiner) and suspensa (Loew) (Aluja et al. 1983, 1989, Dodson 1982, Burk 1983, Morgante et al. 1983, 1993, Nation 1972, Polloni & Silva 1986, Robacker & Hart 1985, Teles da S. et al. 1985). In the cases of fraterculus, ludens, obliqua, serpentina, sororcula, striata and suspensa male mating aggregations (leks) have been reported (Aluja et al. 1983, 1989, Dodson 1982, Morgante et al. 1983, 1992, Sivinski 1989). Within a lek (or outside of it) males typically emit a series of courtship sounds (calling songs) through wing fanning (Webb et al. 1984; Sivinski 1988), release a sexual pheromone (Nation 1972), and usually defend a territory (individual leaf or portion thereof) (Aluja et al. 1983). While calling, individuals preferably position themselves on the underside of a leaf (Dodson 1982, Aluja et al. 1989) and only rarely take off and return to the same spot repeatedly within a bout of calling. Here, I report the unusual calling behavior of Anastrepha robusta (Greene) males. The discovery was made during a study of the natural history of Anastrepha spp. in a mixed chico zapote (Manilkara achras L.) citrus (Citrus sinensis Osb., C. reticulata Blanco) guanabana (Annona muricata L.) coconut (Cocos nucifera L.) orchard in Apazapan, Veracruz, Mexico during 1990. On June 21, 1990 a single, very large fruit fly male was sighted in a Citrus reticulata tree performing a series of elaborate loops with repeated landings within looping bouts (Fig. 1). The specimen was captured and identified as Anastrepha robusta. Anastrepha robusta is a rare species belonging to the robusta group (Norrbom 1988). It has only been reported in Brazil, Panama (type material), Guatemala (type locality) and Mexico (Stone 1942). To date nothing has been reported about its biology, ecology and behavior. Eight calling males were observed after the first sighting (1990) and 2 females were captured in McPhail traps placed in a C. reticulata tree. In 1991, no individuals were sighted or trapped at this site. In 1992, 5 individuals (3 Y & 2 d) were trapped in the same location (C. reticulata tree) but no individuals were sighted. All captured individuals have been placed as voucher specimens in the permanent insect collection of the Instituto de Ecologia, A.C. in Xalapa, Veracruz, Mexico. A summary of the 1990 sightings is provided in Table 1 [note that A. robusta males only call during early morning hours (0700-0930 hours)]. While calling, males performed a mean of 9.5 ? 0.5 (SE) loops min-,. The distance a loop extended from the point of departure varied from loop to loop but ranged between ca. 15 and 40 cm. All looping males were observed in the outer canopy of trees (both C. aurantium and A. muricata) and loops were always performed in wide open spaces between trees or branches. While looping, flies flew on both horizontal and vertical planes. Typically, an individual would take off, fly out into the open on an horizontal plane, loop downward and then fly back to the departing point (leaf). On only two occasions were two males seen calling simultaneously at the same site (males were ca. 15 cm apart on two separate leaves ca. 3 m above the ground in an Annona muricata tree). Never were females seen in the vicinity of looping males.