Natural and synthetic oviposition stimulants forCatolaccus grandis (Burks) females

Analysis of volatiles from feces of released Przewalski's horse (Equus przewalskii) in Gasterophilus pecorum (Diptera: Gasterophilidae) spawning habitat

The absolute dominant species that infests wild population of Przewalski's horse (Equus przewalskii) is Gasterophilus pecorum, and feces of released Przewalski's horse, a habitat odor, plays an important role in mating and ovipositing locations of G. pecorum. To screen out unique volatiles for attracting G. pecorum, volatiles from fresh feces of released horses at stages of pre-oviposition (PREO), oviposition (OVIP), and post-oviposition (POSO) of G. pecorum, and feces with three different freshness states (i.e., Fresh, Semi-fresh, and Dry) at OVIP were collected by dynamic headspace adsorption and determined by automatic thermal desorption GC-MS. Results show that there were significant differences in fecal volatiles within both test conditions. Of the five most abundant volatiles from the five individual samples, the most important volatile was ammonium acetate at OVIP/Fresh, followed by acetophenone (Semi-fresh), toluene (PREO, OVIP and POSO), butanoic acid (OVIP and Semi-fresh), acetic acid (PREO, POSO and Semi-fresh), 1,6-octadiene,3,7-dimethyl-,(S)- (PREO, OVIP and POSO), 1,5,9-undecatriene,2,6,10-trimethyl-,(Z)- (PREO and Semi-fresh) and caprolactam (all conditions), which seem to be critical substances in oviposition process of G. pecorum. The findings may be beneficial to development of G. pecorum attractants, facilitating prevention and control of infection by G. pecorum to released Przewalski's horse.

Attraction of the Larval Parasitoid Spintherus dubius (Hymenoptera: Pteromalidae) to Feces Volatiles from the Adult Apion Weevil Host

The behavioral response of the larval parasitoid Spintherus dubius (Hymenoptera: Pteromalidae) to volatile compounds derived from its Apion weevil hosts was investigated in two-choice bioassays. Odor source candidates were the larval and adult stages of weevils, clover flowers, and feces from adult weevils. Despite S. dubius being a larval parasitoid, the odor of weevil larvae isolated from the clover flowers was not attractive to female parasitoids. Surprisingly, S. dubius females were instead attracted by the odor from the feces of adult weevils. The female parasitoids were similarly attracted to the feces produced by the two main hosts, the red clover weevil (A. trifolii) and the white clover weevil (A. fulvipes). Chemical analysis of the volatile composition of feces produced by the two hosts revealed qualitatively similar odor profiles, correlating with the observed attraction by the parasitoid towards both odor sources. Some of the identified volatile compounds are commonly present in clover plant headspace fractions and may function as a kairomone to facilitate orientation by S. dubius to Apion-infested clover flowers. Larval and adult weevils were not attractive for parasitoid females, whereas, for the white clover weevil-plant association, infested flowers were highly attractive. These data show the use by the clover weevil parasitoid of an alternative source of olfactory information for locating its host.

Anagrus breviphragma Soyka Short Distance Search Stimuli

Anagrus breviphragma Soyka (Hymenoptera: Mymaridae) successfully parasitises eggs of Cicadella viridis (L.) (Homoptera: Cicadellidae), embedded in vegetal tissues, suggesting the idea of possible chemical and physical cues, revealing the eggs presence. In this research, three treatments were considered in order to establish which types of cue are involved: eggs extracted from leaf, used as a control, eggs extracted from leaf and cleaned in water and ethanol, used to evaluate the presence of chemicals soluble in polar solvents, and eggs extracted from leaf and covered with Parafilm (M), used to avoid physical stimuli due to the bump on the leaf surface. The results show that eggs covered with Parafilm present a higher number of parasitised eggs and a lower probing starting time with respect to eggs washed with polar solvents or eggs extracted and untreated, both when the treatments were singly tested or when offered in sequence, independently of the treatment position. These results suggest that the exploited stimuli are not physical due to the bump but chemicals that can spread in the Parafilm, circulating the signal on the whole surface, and that the stimuli that elicit probing and oviposition are not subjected to learning.

A sensitive bioassay for spider mite (Tetranychus urticae) repellency: a double bond makes a difference

Choice bioassays were used to determine repellency of homologous n-alkanes (C(8)H(18)-C(21)H(44)) to spider mites. When tested at 400 μg/cm(2), the C(15)-C(19) alkanes were highly repellent; the C(16) n-alkane, n-hexadecane, was most repellent. Subsequently the EC(50) values, the concentration at which 50% of the mites were repelled, were determined for the C(15)-C(19) n-alkanes and their analogous 1-n-alkenes (C(15)H(30)-C(19)H(38)). The EC(50) value for 1-heptadecene, the C(17) 1-n-alkene, was the lowest observed. Except for the 17-carbon hydrocarbons, the EC(50) values for the n-alkanes were less than those for their analogous 1-n-alkenes. Depending on the compounds evaluated, there was as much as a six-fold difference of repellency between an n-alkane its analogous 1-n-alkene. Thus, the bioassay has sufficient sensitivity to detect behavioral differences associated with the presence or absence of a single double bond. The EC(50) values for the most repellent hydrocarbons were similar to that reported for 2,3-dihydrofarnesoic acid, a naturally occurring repellent isolated from trichome secretions of a wild tomato, Solanum habrochaites, and also were similar to concentrations used to evaluate arthropod repellents. Consequently, this bioassay may be useful for providing a better understanding of the relationships between structures and activities of natural products that are repellent to spider mites.

Nutrition and culture of entomophagous insects

This article reviews the current state of knowledge concerning the nutrition of entomophagous insects and other arthropods. Early nutritional investigations focused principally on the basic dietary and nutritional requirements for beneficial insects. Based on these findings, the first attempts were made to develop mass culture methods and to formulate artificial diets that would allow rearing of parasitoids and predators in the absence of host or prey, as well as the latter's food sources. Although limited success was achieved, these studies established the nutritional foundation for later advances. Recently, attention has focused on the interaction between nutrition, physiology, behavior, and ecology of the different life stages of entomophagous species within a unified concept of nutritional ecology. This approach has resulted in more comprehensive understanding of nutrition, which in turn has facilitated the continuous artificial culture of several parasites and predators. Additional studies have confirmed the importance of supplemental feeding of the adult stages of beneficial insects for maximizing reproduction and longevity. Applications of nutritional ecology to biological control are discussed.