Ruth R. Do Nascimento

Volatile substances from male Anastrepha fraterculus wied. (Diptera: Tephritidae): identification and behavioural activity

Volatile compounds produced by calling males of Anastrepha species have previously been reported from A. ludens and A. suspensa. Both species mate in the afternoon, release a similar range of compounds in different proportions, and only differ in the production of monoterpenes. When calling, male A. fraterculus releases two isomers of the sesquiterpene a-farnesene, three lactones (anastrephin, epianastrephin and (E,E)-suspensolide), and two monoterpenes (limonene and (Z)-b-ocimene). The dimorphic male salivary glands produce and/or store the same isomers of a-farnesene and suspensolide, and four pyrazines. Two of these compounds have been previously reported from male A. ludens and A. suspensa. Salivary glands from virgin calling male A. fraterculus showed behavioural activity when bioassayed with virgin mature female flies, but immature females were not attracted.

Pheromone Analyses of the Anastrepha fraterculus (Diptera: Tephritidae) Cryptic Species Complex

ABSTRACT The South American fruit fly Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) cryptic species complex is presently one of the most studied pest models in terms of speciation and population mating compatibility. The improvement of pest-control techniques has strongly relied on successful implementation of laboratory strains into wild populations. Pheromone communication plays an important role in the mating process in the South American fruit fly. Therefore, the main goal of the present study was to investigate the pheromone composition of 7 different populations, originating from geographically distant locations in Brazil and Argentina. Fourteen volatile compounds were identified in calling male emanations by GC×GC/TOF-MS and the data obtained were subsequently analyzed by multivariate statistics. The pheromone composition varied both quantitatively and qualitatively among the studied populations. These results will serve as the basis for further electrophysiological analyses.

Are the wild and laboratory insect populations different in semiochemical emission? The case of the medfly sex pheromone.

The medfly (Ceratitis capitata) is one of the major agricultural pests controlled through sterile insect technique (SIT) programs. We studied the chemical composition of the volatiles released by calling males from one laboratory and two wild C. capitata populations using two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC × GC/TOFMS) and gas chromatography with electroantennographic detection (GC-EAD). Multivariate data analyses revealed significant differences in the quantitative and qualitative composition of male chemical emanations between the three populations. The GC-EAD analyses of the male emanation of three C. capitata populations revealed 14 antenally active compounds. The volatiles isomenthone, β-pinene, ethyl octanoate, indole, geraniol, bornyl acetate, geranyl acetone, and (E)-caryophyllene are newly reported EAD active constituents of the male pheromone. GC-EAD analyses of the laboratory population indicated that the males and females of C. capitata possess comparable sensitivity to male-produced volatiles. Our results are relevant to the development of a pheromone-based monitoring system and also to the SIT control program.

Comparison of the Volatile Components Released By Calling Males Of Ceratitis capitata (Diptera: Tephritidae) with Those Extractable from the Salivary Glands

Abstract The volatile compounds released by calling males of Ceratitis capitata and those that were extracted from the salivary glands with n-hexane were analyzed by gas chromatography-mass spectrometry. Twelve of the 24 compounds identified in the released volatiles, namely, 2-heptanone, 2,5-dimethylpyrazine, 3-octanone, ethyl hexanoate, methyl heptanoate, 2-ethyl-1-hexanol, limonene, indene, ethyl heptanoate, methyl octanoate, α-trans-bergamotene and (E,E)-α-farnesene, also were detected in the glandular extract. The similarities found in the chemical profiles of the released volatiles and of the salivary gland suggest that the latter is the storage site, and also perhaps the site of synthesis, of some of the pheromone components in this species of fruit fly.

Pygidial Gland of Azteca NR. bicolor AND Azteca chartifex: Morphology and Chemical Identification of Volatile Components

The large paired reservoirs of the pygidial gland of Azteca nr. bicolor and A. chartifex represents the largest exocrine structure in the abdomen. The glands produce a secretion with a strong smell, which the ants release when they are disturbed. Analyses of the secretions by gas chromatography–mass spectrometry (GC-MS) revealed a mixture of iridoids and ketones. A. nr. bicolor contains 2-heptanone (8%) and a mixture of three iridodial isomers, with trans-trans-iridodial as the major component (32%). A. chartifex contains 6-methyl-5-hepten-2-one (13%) and the three isomeric iridodials with cis-trans-iridodial as the principal component (32%).

THE BIOLOGY OF DIATRAEA FLAVIPENNELLA (LEPIDOPTERA: CRAMBIDAE) REARED UNDER LABORATORY CONDITIONS

Abstract Aspects of the biology of the sugarcane pest Diatraea flavipennella (Box 1931) (Lepidoptera: Crambidae), locally named broca-pequena da cana-de-açúcar, reared and maintained under laboratory conditions and fed on an artificial diet have been investigated. The larval stage, which involved 7 instars, continued for a mean period of 34.87 d. Each instar could be characterized by the size of the cephalic capsule, which increased 1.28-fold on average between instars. The mean duration of the pupal stage was 12.75 d. The pupae exhibited sexual dimorphism in that the females were larger than the males, while the latter exhibited a genital pore that was absent in the females. In adult insects, the female/male ratio was 1:1.3. Adult females were on average 28.73 mm in size while the mean value for adult males was only 20.80 mm. Females commenced oviposition on the first d of their adult life and were able to oviposit until d 6. On average each female produced 431.05 eggs during her lifetime, although the majority of eggs were deposited during the first 2 d after emergence.

Behavioural evidence for a female sex pheromone in Cotesia flavipes (Hymenoptera: Braconidae)

Abstract.  The mating behaviour of Cotesia flavipes Cameron, 1891 (Hymenoptera: Braconidae) was observed under laboratory conditions. The results demonstrate that chemical stimuli play an important role in bringing males and females together for mating. Females from this species release chemical compounds to attract males, which exhibit a distinct courtship behaviour divided into three main steps: (i) antennation, (ii) lateral bouncing and (iii) wing fluttering. Ethological tests using hexane extracts from two different parts of the females body (head plus thorax and abdomen) demonstrate that males are more attracted and also display a courtship behaviour when a filter paper containing hexane extracts from the abdomen is presented to them, indicating that the abdomen is the source of the sex pheromone of this species. Naive males of this species respond to hexane extracts of this gland by displaying courtship behaviour. Furthermore, additional tests show that C. flavipes females mate only once, whereas virgin males do not show any preference for virgin or mated females, suggesting that mated females of this species continue to produce sex attractants after mating.

Identification of male-borne attractants in Anastrepha fraterculus (Diptera: Tephritidae)

The South American fruit fly is one of the most destructive polyphagous pests in South America. In this species, males gathered in aggregations emit volatiles that attract females; however, the compounds involved in this task remain unknown. In this study, we investigated the chemical composition of the volatile blend emitted by males aiming to identify the specific compounds within this blend that elicit behavioral responses in conspecific females. For this purpose, we performed chemical and electrophysiological analyses and bioassays. The chemical analyses revealed the presence of 29 compounds in headspace samples of A. fraterculus males, of which six compounds, i.e. α-pinene, limonene, (Z)-3-nonen-1-ol, (E,Z)-3,6-nonadien-1-ol, α-farnesene and (S,S)-(−)-epianastrephin, triggered antennal depolarization in conspecific females. In laboratory bioassays, five out of eight synthetic compounds tested individually elicited more behavioral responses than a hexane control, but only the synthetic mixture composed of all EAD-active compounds triggered behavioral responses in females similar to the responses to the headspace samples of conspecific males. In an experiment under semi-natural conditions, the synthetic mixture was more attractive to females than a hexane control and equally attractive to headspace extracts of males. This study reports the identification of male volatile compounds that act as attractant for A. fraterculus females, which may be useful for the control of this pest in infested orchards.

Current knowledge of the species complex Anastrepha fraterculus (Diptera, Tephritidae) in Brazil

Abstract The study of the species complex Anastrepha fraterculus (Af complex) in Brazil is especially important in a taxonomical, evolutionary and pest management context, because there are evidences that some of them may occur in sympatry. In this review, we analyzed the main results supporting evidences that three cryptic species occur in Brazil. The taxonomical and phylogenetic relationships based on eggshell morphology, adult morphometrics, as well as cytotaxonomy and genetic differentiations are discussed. We also review available information on sexual behavior including acoustic communication of males during courtship and sexual incompatibility; and chemical signals involved in the communication between sexes, with a special focus on sex pheromones. We examined the role of long- and short-range pheromones (male-produced volatiles and cuticular hydrocarbons, respectively), their implications in sexual isolation, and their possible use for chemotaxonomic differentiation of the putative species of the Af complex.

THE PREDOMINANCE OF Diatraea flavipennella (LEPIDOPTERA: CRAMBIDAE) IN SUGAR CANE FIELDS IN THE STATE OF ALAGOAS, BRAZIL

Brazil, the third largest producer of cane sugar in the world, is responsible for approximately 330,000 tons per year or 25% of the total world production (IBGE, 2004). While the state of Alagoas, in north-eastern Brazil, ranks as number three in terms of agricultural and industrial productivity of sugar cane in the country, the potential yield is diminished through damage by pests, mainly insects of the genus Diatraea (Lepidoptera: Crambidae). Two species of Diatraea predominate in Brazil, namely, D. saccharalis Fabricius 1974 and D. flavipennella Box 1931. The former is widespread throughout the country while the second is restricted to Alagoas and a few other states in the north-eastern region (Guagliumi, 1972/73). Studies carried out in Alagoas during the 1970s and 1980s (Risco et al. 1975) indicated that D. saccharalis prevailed (70.12%) over D. flavipennella (29.88%). According to a survey conducted in 1985 by the Entomology Sector of PLANALSUCAR (PLANALSUCAR 1985), however, an inversion of this situation commenced in some areas of the state and D. flavipennella (89.80%) showed preponderance over D. saccharalis (10.20%). Knowledge of the frequencies of occurrence of these two species is of considerable importance to the sugar cane industry because the damage caused by these pests leads to significant loss of yield. Thus, a 1% change in the level of infestation by D. saccharalis gives rise to a reduction of 2.5 kg of sugar per ton of cane collected (Gallo et al. 2002). Because the data regarding the prevalence of the two pests are dated, we have conducted a new survey of the incidence of Diatraea species in the sugar cane plantations of Alagoas. Eight different edaphic and climatic areas in Alagoas were selected for assessment, encompassing the agricultural estates belonging to the sugar cane factories Cachoeira, Cansanção de Sinimbu, Marituba, Santo Antônio, Seresta, Sumaúma, Terra Nova, and Triunfo (Fig. 1). The study was conducted between Sep 2003 and Feb 2004 during the initial phase of sugar cane cultivation and subsequent growth of the culture. Larvae of Diatraea species were collected from severely infested sugarcane plants found in the 8 locations mentioned. The plants were selected on the basis of observable damage to the apical buds and infiltration of larvae into the culms, both of which may lead to the penetration of phytopathogenic micro-organisms and subsequent disease provoking sucrose breakdown. Identification of the species collected was performed on the basis of the morphological characteristics of the larvae as described previously by Guagliumi (1972/73) and Mendonça (1996). The total number of larvae collected from all sampling areas was 3341, of which 78 specimens (2.33%) were D. saccharalis and 3263 (97.67%) were D. flavipennella (Table 1). In all 8 locations studied, the number of specimens of D. flavipennella randomly collected was far greater than that of D. saccharalis , the latter being completely absent in 3 areas. The results clearly demon-