Analysing host location in Uscana lariophaga (Hymenoptera: Trichogrammatidae), an egg parasitoid of bruchids (Coleoptera: Bruchidae), using Cox's proportional hazards model

Abstract

Uscana lariophaga Steffan is an egg parasitoid of the bruchid species Callosobruchus maculatus (Fabricius) and Bruchidius atrolineatus Pic in West Africa, which cause damage in stored cowpea (Vigna ungukulata (Leguminosae)). In a no-choice situation, the attractiveness of some odour sources to the parasitoid was studied in a simple diffusion olfactometer. Cox's proportional hazards model was used for data analysis. The results showed that cowpea beans were more attractive to naive U. lariophaga females than glass beads. Baits with host eggs were more attractive than baits without eggs. Experienced females did not perform any better than naive ones. The relationship between the inclination to fly of the parasitoids, and the baits used, was difficult to interpret. Changes in searching activity between the different weeks of experimentation were observed. Only a small part of this variation could be explained by (absolute) changes in barometric pressure.

Host location in stored cowpea by the egg parasitoid Uscana lariophaga Steffan (Hym., Trichogrammatidae)

“…maculatus Fab. egg odour caused a significant arrestment of U. lariophaga females in the odour side in four out of six treatments, confirming earlier reports (VAN HUIS et al, 1994;ORMEL et al, 1995). Furthermore, walking time in the treated side and the T/C ratio (table 2) increased with increasing egg density, suggesting that the effect of egg odour becomes stronger with higher numbers of eggs.…”

“…U. lariophaga recognizes volatiles from uninfested cowpea seeds, and is attracted by odours from freshly laid C . maculatus eggs (ORMEL et al, 1995). Inside a cowpea granary, when the parasitoid is surrounded by cowpea seeds, plant odours cannot provide directional cues.…”

Patch exploitation by the parasitoids Cotesia rubecula and Cotesia glomerata in multi‐patch environments with different host distributions

“…The steps involved in the leaving tendency (1, 3, 4, 5 and 6) can be represented mathematically by an equation highly similar to the proportional hazards model (1). Factors involved in a tendency to arrive (like step 2) can be formulated by essentially the same type of equation (Ormel, Gort & van Alebeek 1995). In adjustable termination rate models the animal is considered as continually adjusting its probability per unit time to leave (termination rate), according to ‘good’ and ‘bad’ experiences.…”

Influence of barometric pressure on odor discrimination and oviposition by adult plum curculios (Coleoptera: Curculionidae)

“…For example, olfactory discrimination by Cotesia (= Apanteles) glomerata (L.), an endoparasitoid of Pieris sp., was greater during test periods of steadily increasing barometric pressure than during test periods of steadily decreasing or fluctuating barometric pressure (Steinberg et al, 1992). Furthermore, greater numbers of the parasitoid species Uscana lariophaga Steffan arrived at attractive odor sources in a simple dif fusion olfactometer when absolute changes in barometric pressure were large (Ormel et al, 1995). We did not detect many changes in barometric pressure within the 2-hour time frame of our assays but this does not preclude the possibility that changes in barometric pressure over an unknown time frame prior to testing could have markedly influenced our results and account for differences observed between years.…”