Trees or stores? The origin of migrating Prostephanus truncatus collected in different ecological habitats in southern Benin

Abstract

Migrating Prostephanus truncatus (Horn) (Col.: Bostrichidae) were collected weekly with pheromone-baited funnel traps at three different sites in southern Benin for 12 months. One site was located in a primary forest, one in a peri-urban area, and one in a region with intensive agriculture. The sex of the trapped beetles was determined. The gut-content of the specimens was analyzed for remains of lignin and starch, the former indicating recent feeding on woody, the latter on a starchy substrate, such as stored maize or dried cassava. At all locations, the sex ratio of migrating P. truncatus was significantly female-biased, with the greatest proportion of females trapped at the periurban site. At the forest site, most beetles had lignin in their guts, while the proportion of beetles containing starch was highest in the peri-urban site. Approximately equal proportions of beetles with either starch and lignin were trapped in the region with intensive agriculture. The results are discussed with regard to the population dynamics of P. truncatus in different habitats and the flight activity of the beetles.

Sensitivity ofProstephanus truncatus(Coleoptera: Bostrichidae) Flight Activity to Environmental Variables in Benin, West Africa

“…In addition, there is evidence that pheromone traps may be selective on at least two levels by mainly attracting certain parts of the total population. Firstly, Borgemeister et al (1998) and Scholz et al (1997) in southern Benin, NangÕayo (1996 in Kenya, and Birkinshaw (1998) in south eastern Ghana found that 60 Ð75% of the P. truncatus individuals caught in pheromone traps were females. The pheromone lures used in these studies were the same as those used in the current study.…”

“…In most of these countries, the documentation of P. truncatus incidence was based on an initial survey using pheromone traps in addition to inspections of maize and cassava stores. Pheromone trapping has also been used to document the establishment of P. truncatus in forest and savanna habitats in meso America (Rees et al 1990, Tigar et al 1993, Ramṍrez-Martṍnez et al 1994, in East Africa (NangÕayo 1996), and in West Africa (Borgemeister et al 1998, Nansen et al 1999.…”

Flight initiation and flight activity in Prostephanus truncatus (Coleoptera: Bostrichidae)

“…Thus this experiment confirms that P. truncatus reacts to crowding and to the accompanying degradation of the food source with migration. In a food source analysis of migrating P. truncatus, Borgemeister et al (1998b) found that during peak flight activity between January and March at the IITA station in Benin, the majority of the insects contained starch in their guts, indicating that the beetles had recently emigrated from nearby maize or cassava stores. This period of the year coincides with the end of the major storage period in southern Benin (Agbaka, 1996).…”

“…Hence, flight activity in the Mono District must have been partly affected by factors different from those influencing migration near the IITA station. In their analyses of seasonality of flight activity and the origin of migrating P. truncatus, Borgemeister et al (1997 and1998b) concluded, that mainly the availability of host plants and not so much weather factors were responsible for peaks in flight activity. Strong seasonal fluctuations in the flight activity of P. truncatus were also observed in bushland areas of Kenya and Benin (Giles et al, 1995;Nang'ayo, 1996;Borgemeister et al, 1998a).…”

Using elemental profiling to determine intrinsic markers to track the dispersal of Prostephanus truncatus, a pest of stored grain with alternative natural hosts

“…Such analytical approaches have the potential to detect the assimilated diet of organisms, including evidence of natal diets in dispersing adults, in contrast to gut content analyses which reveal recent adult diet (Borgemeister et al, 1998a). Such analytical approaches have the potential to detect the assimilated diet of organisms, including evidence of natal diets in dispersing adults, in contrast to gut content analyses which reveal recent adult diet (Borgemeister et al, 1998a).…”