Norma Robledo

Antennal Sensilla of Toxotrypana curvicauda (Diptera: Tephritidae)

Abstract Antennal morphology and funicular sensilla of male and female papaya fruit fly, Toxotrypana curvicauda Gerstaecker, were studied with light microscopy and scanning electron microscopy. Antennae were 3-segmented, consisting of a scape, a pedicel, a flagellum or funiculus that bears the arista. Antennal segments of males showed a trend toward slightly greater dimensions than those of females, but the differences were not significant. Numerous microtrichia as well as trichoid, basiconic, clavate, and styloconic sensilla were observed on the funiculus, and the sensillar characteristics were similar to those reported for other tephritid species. Males and females did not differ in total number or type of sensilla found on the funiculus, but trichoid and clavate sensilla were significantly larger in females. This difference may be related to female chemoreception of male-emitted sex pheromone and of host plant volatiles.

Influence of host fruit and conspecifics on the release of the sex pheromone By Toxotrypana curvicauda males (Diptera: Tephritidae).

ABSTRACT The release of tephritid sex pheromones depends significantly on the age of the male, the social context (presence of conspecifics) and chemical context (host volatiles). In this study, the influence of host fruit and conspecific (males and females) on the emission of the pheromonal compound 2-methyl-6-vinylpyrazine (2,6 mvp) by Toxotrypana curvicauda (Gerstaecker) males was investigated under laboratory conditions. Males were divided into one control group (nonexposed to treatment) and five experimental groups were placed 1 hr before volatile collection with: 1) host fruit (unripe papaya), 2) two females, 3) two males, 4) host fruit plus two females, and 5) host fruit plus two males. The volatiles were sampled by means of solid phase microextraction and analyzed with gas chromatography-mass spectrometry, with a focus on 2,6 mvp. Males emitted volatiles from the first day after adult emergence. The maximum peak and the temporal pattern of 2,6 mvp release were modified by the presence of host fruit and conspecific males or females. On day 5, males in the presence of fruit maintained a constant release of 2,6 mvp while the presence of conspecific caused a decrease of pheromone release. The release of 2,6 mvp was increased significantly in males exposed to both types of stimuli simultaneously. The stimuli (fruit and conspecifics) modified the release of 2,6 mvp, however the effect depended on male age.

Extraction with SPME and Synthesis of 2-Methyl-6- vinylpyrazine by a 'One Pot' Reaction Using Microwaves

A synthesis of 2-methyl-6-vinylpyrazine was carried out by way of a ‘one pot’ reaction. In order to establish the efficiency of this synthesis the extraction of the volatiles released by male papaya fruit flies was performed by SPME (solid phase micro-extraction). The compound was separated and identified using GC/MSD (gas chromatography/mass spectrometry detector).

Effects of male age and mating status on response to the female sex pheromone of Copitarsia decolora (Lepidoptera: Noctuidae)

Abstract The effects of male age and mating status on the behavioral response of Copitarsia decolora (Guenée) males to the glandular extract of the female sex pheromone were studied by conducting wind tunnel bioassays and electroantennography (EAG). To study the effect of age, 2–3, 4–5, 6–7, 8–9, 10–11 day old males were used to measure attraction in the wind tunnel. To study the effect of age on virgin male antenna depolarization, Individual males 3-, 6- and 9-days old were used. The effect of male mating status was studied with 4–6 day old males and subsequent pheromone response was measured after a period of 24 and 48 h. Both male age and mating status significantly affected male response to the female sex pheromone. In the wind tunnel, male attraction to the extract reached its maximum in males 4–7 days old and then decreased as moth age increased. The glandular extract provoked a significantly greater depolarization of the antennae of 6 day old males than in 3 and 9 day old males. In the wind tunnel, virgin males were more attracted to female extracts than mated males. Significantly greater depolarization was observed in the antennae of virgin than mated males.

Discrimination of Chemical Stimuli of Immature Papaya Fruit Oviposited and Not Oviposited In by Female Toxotrypana curvicauda 1

Abstract. Attraction response of female Toxotrypana curvicauda (Gerstaecker) to volatile compounds from immature fruit of papaya (Carica papaya L.) and of gravid females to papaya fruit oviposited and not oviposited in was studied with the aid of an olfactometer. Response of virgin and mated females (4–6 days old) to immature papaya fruit covered or not with Lycra netting was evaluated. After greatest attraction response had been recorded, extracts were obtained by dynamic aeration. The compounds were identified by gas chromatography-mass spectrometry. Attraction response of females to papaya extracts obtained using three solvents was studied by bioassays in a wind tunnel. From the extracts were identified eight compounds: an aldehyde, two heterocompounds, four hydrocarbons, and a terpene. Hexanic extract resulted in most landing by virgin females on an odor source (10%); however, no statistically significant differences were observed among treatments. A synthetic blend was created, based on the hexanic extract compounds, and its attraction was evaluated. Virgin females were more attracted; however, only 5% landed on the odor source. Mostly only mated females were attracted to hexanic extract (15% of long flights and 5% landings). Nevertheless, as demonstrated in electroantennography responses, virgin and mated females were attracted to the synthetic blend, with the largest polarization values. Mated females were more attracted to fruit not oviposited than oviposited in, implying they evade intra-specific competition.

Food Quality Influences Ovarian Development in Scyphophorus acupunctatus (Coleoptera: Dryophthoridae)

Abstract This paper describes the anatomy of the female reproductive system of the agave weevil, Scyphophorus acupunctatus Gyllenhall (Coleoptera: Dryophthoridae). This insect is considered a primary pest of agave (Agave spp.) (Asparagaceae) and tuberose (Polianthes tuberosa L.) (Asparagaceae) in Mexico. Developmental biology and ovarian maturation of laboratory-reared S. acupunctatus fed a meridic diet was compared with individuals fed tuberose bulbs. Ovarian maturation was classified according to ovariole and follicle differentiation, as well as the presence of follicular relics. This classification yielded 1 parous and 3 nulliparous stages. We found that ovarian maturation was delayed for those weevils fed the meridic diet compared with those fed tuberose bulbs. Also, the greatest number of ovarian follicles occurred in individuals fed tuberose bulbs; however, this relationship changed with the age of the insect. Proximal length and follicular area also varied according to age and type of diet. We believe that the ovarian developmental stages described here for S. acupunctatus could be a useful method to monitor parity status of field populations when assessing the effectiveness of control programs for this weevil pest.

Modification of Behavioral Response in Copitarsia decolora (Lepidoptera: Noctuidae) Due to Pre-Exposure to Sex Pheromone and Host Plant Volatiles

Abstract In this study we assessed the effect of pre-exposure to host sex pheromones and plant volatiles on the response of virgin males and mated females of Copitarsia decolora (Guenée) (Lepidoptera: Noctuidae), by using glandular extracts of virgin females and host volatile extracts in bioassays conducted in a wind tunnel. Four-day-old insects, either virgin males pre-exposed to glandular extracts of the sex pheromone or mated females pre-exposed to host volatiles, were evaluated 2, 24, and 48 h after pre-exposure. In both sexes, pre-exposure and a subsequent attraction response at 2 h resulted in an inhibitory effect on the olfactory response. Recovery in the olfactory response was observed at 24 and 48 h; however, it took males a shorter activation time when compared with control insects. A brief pre-exposure of insects provoked a short-term (2 h) inhibition of the response to the olfactory stimulus. Consequently, as an integral part of strategies for the management of this pest species, the study of the ecological implications of such inhibition should be considered.

A new component of the male papaya fruit fly (Diptera: Tephritidae) sex pheromone

Summary In addition to the major component, 2-methyl- 6-vinylpyrazine, 2,5-dimethyl-3-vinylpyrazine was collected as a minor component from calling male papaya fruit flies Toxotrypana curvicauda Gerstaecker (Diptera: Tephritidae). Volatile chemicals emitted by calling males were identified by gas chromatography/mass spectrometry detector analyses. Attraction response was verified by wind tunnel bioassays for the male volatile collections and for both synthetic pyrazines. The percentages of attraction to the source caused by each pyrazine were similar to those caused by the male volatile collection; however, only a blend of the pyrazines resulted in a similar percentage of landings on the source.