Infestation of maize by Prostephanus truncatus initiated by male‐produced pheromone

Self Cite

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.

Section: Discussionsupporting

confidence: 87%

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

Borgemeister

Tchabi

Scholz

1998

Self Cite

“…Yet, sex ratios among P. truncatus caught with single males on maize cobs in a maize-growing region, were also female-biased (ca. 64% females; Scholz et al, 1997), and, as pheromone-perception thresholds of males and females hardly differ (Scholz, 1997), these results suggest that females make up the majority of migrating P. truncatus. However, the sex ratios among dispersing P. truncatus may depend on the breeding habitat they emigrate from: Traps baited with synthetic pheromone caught nearly balanced sex ratios within forests (Ramirez-Martínez et al, 1994;C.…”

Section: Discussionmentioning

confidence: 62%

Flight initiation in Prostephanus truncatus: influence of population density and aggregation pheromone

Scholz

Borgemeister

Markham

et al. 1997

Self Cite

The influence of population density and aggregation pheromone were investigated as possible flight initiating factors for Prostephanus truncatus (Horn) (Col.: Bostrichidae). Maize grains (175 g in glass jars) were infested with 20, 50, 150 or 300 beetles, all of which were removed after 2 weeks. Flight initiation of the progeny was observed over a period of 4 weeks, with and without the synthetic aggregation pheromone of P. truncatus. Addition of the synthetic pheromone had no influence on the number of beetles taking off. The number of beetles dispersing increased with growing initial and progeny densities. Dispersal rates (% of total progeny dispersing) rose with declining rate till they reached a maximum at ca. 33%. Of the beetles dispersing, 74% left the cultures between 18.00 and 20.00 hours. Surviving progeny per female decreased with increasing initial density. Sex ratios in the initial cultures and in the F1 were ca. 1:1, whereas a higher proportion of females (67%) was found among the dispersing beetles.

“…If male R. dominica do release pheromone signals in order to attract suitable mates, then a stronger response from females than males could be expected. A stronger female response has in fact been reported for the related species, P. truncatus, in both field (Scholz et al, 1997a; and laboratory experiments (Hodges & Dobson, 1998). In the case of R. dominica, the fact that males are relatively more attracted than females to host odours suggests they may be more highly adapted to seek out new hosts from which they can attract mates while females are more inclined to locate a suitable food source by following the pheromone signals produced by males.…”

Section: Difference In Response Between Males and Femalesmentioning

confidence: 78%

Host odours enhance the responses of adult Rhyzopertha dominica to male‐produced aggregation pheromone

Bashir¹,

Birkinshaw²,

Hall³

et al. 2001

The behavioural responses of adult male and female Rhyzopertha dominica (Coleoptera, Bostrichidae) to blends of host volatiles and male‐produced aggregation pheromone were observed in a four‐arm airflow olfactometer. The odour sources used were five pheromone‐releasing males each on a single maize grain (lower maize‐volatiles blend), five pheromone‐releasing males on 500 g of maize (higher maize‐volatiles blend) or the host volatiles emanating from 500g of maize (maize volatiles alone). Multiple‐choice tests, in which volatiles from all three odour sources were presented in the exposure chamber at the same time, were used to study odour preferences of the males and females. Both sexes showed strongest attraction to the higher maize volatile blend but there were significant sex differences in response to the odour sources. Males spent significantly more time than females in the zone with only maize volatiles, and females spent significantly more time in the higher maize‐volatiles zone. However, when odour sources were offered singly, females gave numerically greater responses than males to all sources although this difference was statistically significant for only the lower maize‐volatiles blend. As males are more attracted than females to host odours alone it is suggested that they may be more highly adapted to seek out new hosts while females are more inclined to locate a food source by following the pheromone signals produced by males. However, both sexes responded most strongly to the odour source comprising aggregation pheromone with the higher proportion of maize volatiles.