ABSTRACT
The role of various olfactory and visual stimuli was studied in host-plant finding by the asparagus fly Plioreocepta poeciloptera (Schrank), a monophagous monovoltine tephritid causing serious damage to asparagus spears. Volatiles released by asparagus plants were extracted by diethyl ether after cryotrapping concentration, and identified by gas chromatography-mass spectrometry. Twelve of the 13 compounds identified were tested using electroantennography to measure the response of the fly. Behavioural response was analysed using two different flight tunnels according to circadian rhythm, age and sex of adults, presence of the plant and of different coloured lures, presence of a male congener, or exposure to four pure asparagus odour compounds that elicited responses in electroantennography, i.e. hexanal, (E)-2-hexenal, (Z)-2-hexen-1-ol and decanal. Data showed that males locate the host plant more quickly than females. Females are attracted mainly by the blend of plant odour and male pheromone. Both sexes respond to a complex of stimuli only during the afternoon. These findings will be helpful in developing new and effective approaches to control this pest insect.
Subject(s)
Asparagus Plant/physiology , Asparagus Plant/parasitology , Tephritidae/physiology , Animals , Asparagus Plant/chemistry , Behavior, Animal/physiology , Circadian Rhythm , Female , Male , Odorants , Pest Control, Biological , Smell/physiology , Vision, Ocular/physiologyABSTRACT
A comparison of the walking locomotory reactions of flightless and flight formCallosobruchus maculatus males when subjected to an air current scented with female sex pheromone was undertaken in a tubular olfactometer. The pheromone was delivered to the males either as short pulses or as a continuous flow. To analyze the males' reactions, three behavioral sequences were defined (sequence 1: male sensitivity/arousal; sequence 2: male reactivity; sequence 3; male progression and source location). Although flightless and flight form males were sensitive and reactive in all experiments, their locomotory displacement differed depending on the stimulus conditions. The flightless form males' response remained roughly the same whatever the stimulus conditions (i.e., they always reached the pheromone source). In contrast, the flight form males displayed a markedly reduced response when subjected to a continuous stimulation, indicating that intermittent on-off pheromone stimulation is required in order to sustain their upwind walking progress. This effect could be the result of sensory adaptation and/or habituation in the central nervous system of the flight form, requiring a flickering signal that is unnecessary for the flightless one.
ABSTRACT
The bean weevil (Acanthoscelides obtectus) and its preferential host plant Phaseolus vulgaris probably originate from Central or South America. Acanthoscelides obtectus populations have developed for many years in varied and relatively isolated ecosystems in these regions. The influence of the host and of copulation on reproductive activity was studied in four Colombian insect populations from medium (2000 m) and low altitudes (1200 m). Most medium altitude strains of females do not produce oocytes in the absence of hosts or of copulation. These external stimuli can still influence oogenesis after a long period. Virgin females of low altitude strains produce oocytes early in imaginal life and oviposit rapidly in the presence of the host or after copulation. These characteristics can be maintained for many generations.The different strains react differently to a change of thermoperiod. It is suggested that the strain differences are related to the climatic and ecological conditions prevailing at the various altitudes in the Andes; differences are also apparently related to the reproductive cycle of the host plant, which is ingested by the larvae.
