Víctor R. Castrejón-Gómez

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.

Calling Behavior of Mass-Reared and Wild Anastrepha serpentina (Diptera: Tephritidae)

Abstract The calling behavior of mass-reared and wild males of Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae) was studied both in the laboratory and in field cage tests. In the laboratory, density (1, 5, and 10 males per container), age, and hour of day significantly affected calling behavior. Mass-reared males called independently of density, whereas wild males only called at densities of 5 and 10 individuals. Males of both strains started calling when they were 5–7 d old. The daily pattern of male calling was similar in both strains, starting at 0730 hours, and reaching a peak at 1330–1630 hours. Field cage tests showed that mass-reared males started calling when they were 5 d old; the period of peak calling was when males were 8–9 d old. In contrast, wild males began calling when they were 10 d old, reaching peaks when males were 13, 15, and 18 d old. Wild males tended to form leks to call during each day of the experiment, whereas mass-reared males only formed leks during 2 d, both strains displaying very low levels. During field cage tests, males, independently of strain, displayed two calling peaks, one peak in the morning and one peak in the afternoon, whereas males observed in the laboratory only showed a single calling peak. The results are discussed in view of the effects of mass rearing A. serpentina males in relation to potential use of the sterile insect technique.

Sensory Organs in the Antennae of Phyllophaga obsoleta (Coleoptera: Melolonthidae)

Abstract The antennal flagellum of the melolontid beetle Phyllophaga obsoleta Blanchard consists of three terminal plates of lamellae: proximal, middle, and distal. Six types of sensilla were identified on the internal and external surfaces of lamellae from both sexes: placodea (PLAS), basiconica (BAS), coeloconica (COS), auricilica (AUS), chaetica (CHS), and trichodea (TRS). The first four types have been considered as chemoreceptor sensilla and the last two as mechanoreceptor sensilla. The sensilla from the internal and external surfaces of each of three lamellae present in the antennal club from both sexes were mapped by scanning electron microscopy. PLAS were abundant and followed a uniform pattern of distribution on both internal and external surfaces of lamellae from both sexes. Males antennae present a higher number of PLAS in comparison with females antennae. BAS are more abundant in males than in females and follow a more aggregated distribution than PLAS. AUS were included within the BAS group. COS are scarce and only observed on the internal surfaces of all lamellae. TRS and CHS are only present on the periphery of the lamellae. Most sensillar types identified were more abundant in males than in females. The higher number of PLAS observed in males lamellae compared with females lamellae suggests that these sensilla may be involved in sex pheromone reception.

Antennal sensilla of Anastrepha serpentina (Diptera: Tephritidae).

ABSTRACT The antennal sensilla of Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae) adults were studied by means of scanning electron microscopy. Both sexes have the same form and number of antennal segments. The scape and the pedicel are covered entirely by microtrichia. In the distal part of both segments, a series of longitudinally striated hairs was observed, originating in a flexible socket and ending in a pointed tip. Six types of sensilla were observed in the funiculus: 1) thick-walled multiporous pitted sensilla subtype I and subtype II, 2) thin-walled multiporous pitted sensilla long subtype I and medium length subtype II, 3) basiconic sensilla, 4) multiporous grooved sensilla, 5) clavate sensilla, and 6) an olfactory pit with two small conical and striated sensilla inside. Furthermore, there is a large quantity of microtrichia surrounding the entire funiculus. In the proximal dorso-lateral region of the funiculus, there are trichoid aristae composed of two short segments and one large segment, which have fixed base bristles or tactile hairs without membranes.

Sense Organs on the Antennal Flagellum of Leptoglossus zonatus (Heteroptera: Coreidae)

ABSTRACT For the first time, antennal sensorial organs of Leptoglossus zonatus (Dallas) (Heteroptera: Coreidae) are described through scanning electron microscopy. The antennae are formed by a scape, pedicel, and a flagellum that is composed of two flagellomeres and is the main bearer of sensorial organs. Five types of sensory structures were identified: Trichoid sensilla, basiconic sensilla, coeloconic sensilla, campaniform sensilla, and placoid sensilla. Trichoid sensilla were divided into five subtypes. The large striated trichoid sensilla have almost straight longitudinally striated cuticles and were present throughout the antenna. Flattened trichoid sensilla were variable-sized curved hairs distributed from the base of the scape to the distal end of the first flagellomere. Small striated trichoid sensilla were found mainly on the antenna distal flagellomeres. Smooth trichoid sensilla were located at the distal end of the scape and along the entire length of the pedicel, and are the least abundant type on the antenna. Small smooth trichoid sensilla were found precisely on the joints between the pedicel and scape. Based on size and shape, the basiconic sensilla were also divided into five subtypes (Bs1, Bs2, Bs3, Bs4, and Bs5). These all are rod-shaped. Coeloconic sensilla were found exclusively on the second flagellomere of the flagellum. Just one campaniform sensilla on each antenna was located on the second flagellomere of the flagellum. Finally, a group of 10 oval placoid organs were found at the scape base, in proximity to the joint connecting the antenna to the insects head.

The Metathoracic Scent Gland of the Leaf-Footed Bug, Leptoglossus zonatus

Abstract The metathoracic scent gland of 25-day-old adults of both sexes of the leaf-footed bug, Leptoglossus zonatus (Dallas) (Heteroptera: Coreidae), are described based on optical microscopy analysis. No sexual dimorphism was observed in the glandular composition of this species. The gland is located in the anteroventral corner of the metathoracic pleura between the middle and posterior coxal pits. The opening to the outside of the gland is very wide and permanently open as it lacks a protective membrane. In the internal part, there is a pair of metathoracic glands that consist of piles of intertwined and occasionally bifurcated cellular tubes or columns. These glands discharge their pheromonal contents into the reservoir through a narrow cuticular tube. The reservoir connects with the vestibule via two opposite and assembled cuticular folds that can separate muscularly in order to allow the flow of liquid away from the insect. The external part consists of an ostiole from which the pheromone is emitted. The ostiole is surrounded by a peritreme, a structure that aids optimum pheromone dispersion. The described gland is of the omphalien type.

Evidence of a sex pheromone and daily calling pattern of females of Zamagiria dixolophella (Lepidoptera: Pyralidae).

ABSTRACT Evidence of a sex pheromone released by sapodilla bud borer, Zamagiria dixolophella Dyar (Lepidoptera: Pyralidae), females was obtained under field conditions. Delta type traps baited with 2-d-old virgin females captured wild males in a sapodilla (Manilkara zapota (L.) van Royen) plantation. Once the existence of the sex pheromone was demonstrated, the following study was undertaken to describe calling behavior of Z. dixolophella under laboratory conditions. The calling position observed in this moth is similar to that reported for other species of this subfamily. A single period of calling was observed. The calling observed is of the continuous type and was observed only during scotophase. The females initiated calling when 1-d-old. The maximum number of insects calling was observed in 2-3-d-old females between the fourth and eighth h of scotophase. Calling in these females is controlled by a circadian rhythm. The results are discussed in view of the importance of later studies related to the identification of the sex pheromone.

Effect of four multiple nucleopolyhedrovirus isolates on the larval mortality and development of Spodoptera exigua (Lepidoptera: Noctuidae): determination of virus production and mean time to death

Abstract The biological activity of 4 Mexican isolates (SeSIN6, SeSIN8, SeSLP6, and SeSLP8) of the homologous multiple nucleopolyhedrovirus SeMNPV and their effects on the development of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), were studied. An exotic isolate of SeMNPV from the United States (SeUS2) was used as a reference. Early third-instar larvae were inoculated with 5 × 106 occlusion bodies per mL, resulting in 78% mortality for SeUS2 and approximately 90% mortality for each of the 4 Mexican isolates at 144 h post-inoculation. At 168 h postinoculation, 100% mortality was obtained in all cases. All of the isolates, including SeUS2, significantly reduced the body weights of S. exigua larvae compared with the control larvae; however, at 120 h post-inoculation, the differences among isolates were not significant. All of the isolates reduced the development time of third-instar S. exigua larvae (range: 1.2– to 1.6–fold) compared with the control larvae. An independent experiment was performed to determine production of occlusion bodies and mean time to death. Third-instar S. exigua larvae (15 h after molting) were inoculated with each isolate using the same concentration mentioned above. The occlusion body production rate was similar among all isolates. The isolates SeUS2, SeSLP6, and SeSLP8 yielded the fastest mortality (range: 187–191 h). Thus, the biological activities of the Mexican SeMNPV isolates were similar to the activity of the exotic isolate, indicating that these indigenous viruses are promising for the biological control of S. exigua in Mexico.