Leopoldo Cruz-López

Antennal Sensilla and Electrophysiological Response of Male and Female Spodoptera frugiperda (Lepidoptera: Noctuidae) to Conspecific Sex Pheromone and Plant Odors

Abstract The olfactory system of male and female Spodoptera frugiperda (J. E. Smith) was studied by examining the morphology and distribution of antennal sensilla and determining the responses of both sexes to conspecific female sex pheromone components and plant volatiles using electroantennography (EAG). Seven types of sensilla were observed on the flagellum of the antennae: trichodea, chaetica, coeloconica, styloconica, auricilica, squamiformia, and basiconica. Only one type of trichodea sensilla was found on the antennae of both sexes, but these sensilla were more abundant on male than on female. EAG records of both sexes to 10-μg stimulus loads of six pheromone components showed that (Z)-7-dodecenyl acetate (Z7–12: Ac) and (Z)-9-dodecenyl acetate (Z9–12: Ac) elicited larger responses than those evoked by (Z)-11-hexadecenyl acetate (Z11–16: Ac), (Z, E)-9,11-tetradecadienyl acetate (Z9, E11–14: Ac), (Z, E)-9,12-tetradecadienyl acetate (Z9, E12–14: Ac), and hexane in female antennae. In the case of male antennae, (Z)-9-tetradecenyl acetate (Z9–14: Ac) and Z9, E12–14: Ac evoked larger EAG responses than those elicited by Z7–12: Ac, Z11–16: Ac, Z9, E11–14: Ac, and hexane. The compounds that selectively evoked larger EAG responses from males than females were Z9, E12–14: Ac, and Z9–14: Ac. Dose-response experiments showed that, at the lowest dose tested, Z9–14: Ac and Z9, E12–14: Ac elicited larger EAG responses than Z9–12: Ac and Z7–12: Ac in male antennae. At the highest doses tested, the diene elicited the largest EAG responses. In the case of female antennae, the dose, but not the pheromone component, had a significant effect. Male and female responses to 10-μg stimulus loads of 16 plant volatiles showed that hexan-1-ol evoked larger EAG responses in comparison with those elicited by hexanal, (E)-3-hexenol, 2-carene, phellandrene, limonene, β-pinene, and hexane. The response of male antennae was significantly stronger than the female. Dose-response experiments showed that both sexes appeared to be most sensitive to alcohols, particularly at the highest dose tested.

Selective Oviposition by Aedes aegypti (Diptera: Culicidae) in Response to Mesocyclops longisetus (Copepoda: Cyclopoidea) Under Laboratory and Field Conditions

Abstract The influence of predacious Mesocyclops longisetus Thiebaud on the selection of oviposition sites by prey Aedes aegypti (L.) was studied under laboratory and field conditions. In both cases, gravid Ae. aegypti females were significantly more attracted to ovitraps containing copepods or to ovitraps with water in which copepods were held previously than to distilled water. Monoterpene and sesquiterpene compounds including 3-carene, α-terpinene, α-copaene, α-longipinene, α-cedrene, and δ-cadinene were found in hexane extracts of copepods by gas chromatography and mass spectrometry analyses. These compounds may be responsible for attracting gravid Ae. aegypti females and may increase the number of potential prey for the copepod.

Chemical ecology of triatomine bugs: vectors of Chagas disease.

Abstract. Knowledge of chemical ecology of haematophagous triatomine bugs (Hemiptera: Heteroptera: Reduviidae) could be of practical value because this polyphyletic subfamily includes species of medical importance, such as vectors of Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), the aetiological agent of Chagas disease. For particular species of Dipetalogaster, Panstrongylus, Rhodnius and Triatoma, therefore, we review information on exocrine glands and products, interpreting their apparent roles as semiochemicals in the aggregation, alarm, defence, host‐finding and sexual behaviour of these Triatominae.

A New Potential Attractant for Anastrepha obliqua from Spondias mombin Fruits

Nonirradiated males and females of Anastrepha obliqua (Macquart) were attracted to and landed more frequently on ripe fruits of Spondias mombin L. than on artificial fruit in wind tunnel bioassays. Porapak Q volatile extracts of S. mombin were also attractive and elicited landing on artificial fruit for both sexes. Combined gas chromatographic–electroantennographic detection (GC-EAD) analysis of volatile extracts showed that nine volatile compounds elicited repeatable antennal responses from females and males. The EAD-active compounds were identified by GC–mass spectrometry (MS) as follows: ethyl butyrate, isopropyl butyrate, hexan-1-ol, propyl butyrate, isobutyl butyrate, ethyl hexanoate, isopentyl butyrate, ethyl benzoate, and ethyl octanoate. In wind tunnel bioassays, males and females were attracted and landed more frequently on lures containing the nine-component blend of synthetic compounds than on unscented controls. Field cage bioassays showed that multilure traps baited with the nine-synthetic blend captured significantly more A. obliqua than traps baited with hydrolyzed protein or water.

Is Host Size an Indicator of Quality in the Mass-Reared Parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae)?

ABSTRACT Diachasmimorpha longicaudata (Ashmead) is an endoparasitoid of fruit flies reared for augmentative biological control of several species of Anastrepha in Mexico. During the production of D. longicaudata different sizes of parasitoids are produced depending on the host size. Here, we investigated whether host size influences the biological and behavioral parameters of the wasp that emerged under laboratory conditions. Three different sizes of host (small, medium, and large) were used for the experiments. Host size significantly affected the number of parasitoids emerged as greater number of parasitoids emerged from medium size hosts compared to small and large hosts. The ratio of females to males did not differ among the groups. Host body size influenced life expectancy of parasitoid females and males deprived of food, and parasitoids that emerged from large hosts lived longer. In contrast, host body size did not significantly influence the life expectancy of parasitoid females and males provided with food ad libitum. Host body size also affected gross and net fecundity of emerged parasitoids; females that emerged from medium and large host larvae were more fecund. Host size did not affect most of the behavioral parameters evaluated, except the time of landing on source. Females that emerged from large host larvae spent less time before landing on a host source than females from the smaller hosts. Host body size did not affect the different trajectory indices evaluated, except the mean walking speed of D. longicaudata. Females developed in large hosts showed an increase walking speed compared to females from medium and small hosts.

Response of the Fruit Fly Parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) to Mango Fruit Volatiles

Abstract The response of Diachasmimorpha longicaudata (Ashmead) females to mango fruit that were intact (healthy), mechanically damaged, or infested with Anastrepha ludens (Loew) larvae, and their respective hexanic and methanolic extracts, was studied using behavioral, electrophysiological, and chemical techniques. Female parasitoids significantly preferred to visit infested mangoes and their extracts over healthy and mechanically damaged mangoes in wind tunnel and field cage bioassays. This suggests that the presence of the larvae inside the fruit is of clear importance in the host location behavior performed by this species. Methanolic extracts of infested mangoes evoked a significant electroantennography (EAG) response in female antennae compared with the responses elicited by solvent, healthy, and mechanically damaged mango extracts, but EAG response to hexanic extracts of infested mangoes was only significant compared with solvent control. Most of the compounds found in infested mango hexanic extracts were commonly found in healthy and mechanically damaged mango hexanic extracts, except 2-phenylethyl acetate, which seems to be exclusively present in infested mangoes. Also, infested mango extracts contain several compounds in higher amounts compared with the other two types of mangoes, as do the methanolic extracts from infested mangos. These differences could explain why female parasitoids preferred to visit infested mangos, with their correspondent methanolic and hexanic extracts. Our results suggest that this species uses a complex mixture of compounds for host location.

Effect of post-teneral diets on the performance of sterile Anastrepha ludens and Anastrepha obliqua fruit flies

The effect of post‐teneral diets on the mating performance, pheromone production and longevity of sterile Anastrepha ludens and Anastrepha obliqua fruit flies (Diptera: Tephritidae) was investigated. Enriched pre‐release diets improved male mating performance. Wild and sterile males fed on mango and orange fruits achieved the greatest copulatory success, followed by those fed on a 3 : 1 sugar : yeast (SY) diet. Males fed only on a sugar diet achieved the lowest number of matings. The mean numbers of copulas achieved by wild males were significantly higher than those by sterile males fed on a sugar‐only diet, while there were no significant differences between wild males and sterile males fed on yeast diets. There was a trend of reduced mean number of copulas as the proportion of yeast was reduced in the diet, but differences were not significant. Pre‐release diets had a significant effect on pheromone production. Males fed on a 3 : 1 SY diet produced the greatest amount of the three main pheromone components in A. ludens males and two major components in A. obliqua males, followed by males fed on fruits or pasteurized fruit juice. Males fed on a sugar only diet produced the lowest amounts. The longevity response to post‐teneral diets was complex. The most yeast‐rich diet and the poorest diet (sugar only) resulted in the lowest life expectancies. Flies fed on 24 : 1 SY diets showed the highest life expectancies for both males and females of the two species. Considering the tradeoffs between mating performance and longevity, the 24 : 1 SY diet would be recommended for programmes integrating the sterile insect technique, but the effects of these diets on field survival and dispersal still need to be investigated.

A Reinvestigation of Brindley’s Gland Exocrine Compounds of Rhodnius prolixus (Hemiptera: Reduviidae)

Abstract A chemical, electrophysiological and behavioral study was carried out to analyze the volatile compounds of the Brindley’s gland of Rhodnius prolixus Stål. Six compounds were found in the Brindley’s gland of males and females: acetic, isobutyric, caproic acids and three compounds not identified. The mass spectra of the unidentified compounds have the appearance of a propionate ester, a butyrate ester and a valerate ester. There was no difference in the concentration of these compounds in the glands of males and females. The major component was isobutyric acid. The electroantennographic (EAG) evaluation of isobutyric, acetic, and caproic acids elicited weak responses. With both sexes, the EAG responses for the acids were no different from the control response at any of the doses evaluated (1, 10, 100, and 500 μg). The behavioral response of males and females to acetic, isobutyric, and caproic acids at 1, 5, and 10 μg and binary and tertiary mixtures of the three compounds was evaluated in a Y-olfactometer. Males showed preference for acetic acid at a dose of 1 μg, but not at 5 or 10 μg. Females showed preference for this compound at the dose of 5 μg. Males showed preference for isobutyric acid at 1 and 5 μg, but not at 10 μg. Females did not show any preference for isobutyric acid. Males were attracted to caproic acid at the dose of 1 and 10 μg. Females were attracted to the caproic acid. Males, but not females, preferred the mixture of acetic and isobutyric acids over control. Neither males nor females showed preference for the mixture of acetic and caproic acids or hexane control. Females, but not males, were attracted to the mixture of the isobutyric and caproic acids. Only males showed a positive response for the tertiary mixture of the acids.

BEHAVIORAL AND ELECTROPHYSIOLOGICAL RESPONSES OF THE MEXICAN FRUIT FLY (DIPTERA: TEPHRITIDAE) TO GUAVA VOLATILES

Abstract The behavioral and electrophysiological responses of males and females of the Mexican fruit fly Anastrepha ludens (Loew) to guava (Psidium guajava L.) volatiles were investigated in laboratory tests. Males and females were significantly more attracted and landed more often on guava fruits than yellow spheres used as control in the wind tunnel. Also, both sexes were more attracted to Porapak Q extracts of guava than to solvent controls. Gas chromatography-electroantennographic detection (GC-EAD) analysis of the behaviorally active extracts showed that consistently eight and seven compounds elicited antennal response from male and female, respectively. The compounds were identified by gas chromatography-mass spectrometry (GC-MS) as ethyl butyrate, (E)-3-hexenol, (Z)-3-hexenol, hexanol, ethyl hexanoate, hexyl acetate, (Z)-3-hexenyl butyrate and ethyl octanoate. The electrophysiological activity of the identified compounds at three different doses was evaluated with electroantennography (EAG). An analysis of covariance of the EAG amplitude revealed that synthetic chemicals, sex, dose, and the synthetic chemical × dose interaction significantly influence the antennal response of A. ludens. Males and females were significantly more attracted to septa loaded with the eight-component synthetic blend compared to solvent controls in the wind tunnel.

Chemical and Tactile Cues Influencing Oviposition of a Generalist Moth, Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract The current study was undertaken to investigate the role of the chemical and tactile cues in host–plant selection by Spodoptera frugiperda (Smith). Adult female S. frugiperda seemed not to depend on plant volatiles for orientation to host plants. In general, females oviposited more on control areas than on areas treated with leaf extracts of corn, cotton, and tomato. This outcome was independent of extraction duration (1 or 60 min) or solvent (hexane or methanol). The hexane extract of corn inhibited oviposition at doses of 1 and 0.2 g/ml but not at 0.005 and 0.001 g/ml. The methanolic leaf extract decreased oviposition at dosages of 1, 0.2, and 0.005 g/ml but not at a dosage of 0.001 g/ml. S. frugiperda females deposited more eggs on grooved or pitted surfaces than on smooth surfaces. Tactile cues seemed to be highly important during oviposition and could neutralize the deterrent effect of the corn leaf extracts; females oviposited on grooved surfaces independently of the presence or absence of leaf extracts.