Leam Sreng

Cuticular extracts inducing aggregation in the German cockroach, Blattella germanica (L.).

German cockroaches Blattella germanica (L.) are gregarious insects. An aggregation pheromone contributes to the maintenance of aggregates. Choice experiments checked the efficiency of different solvents, i.e. dichloromethane, methanol and pentane, in extracting attractive substances and compared the attractiveness of extracts of different parts of the body. Dichloromethane and pentane were the most efficient solvents tested for extracting the attractive substances. Methanol whole body extracts appeared inefficient to induce aggregation. The proportion of larvae attracted to conditioned papers decreased in relation to the size of cuticular surface washed, from whole body to half-body and again to a section of the body cut in three. Attractive substances appear to be present on all parts of the body. Chemical analysis by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) showed that the active extracts contained only cuticular hydrocarbons. In addition to behavioural tests, differences between the composition of methanol extracts and that of the extracts for the other two solvents were revealed by GC. These results indicated that the cuticular hydrocarbons operate as an aggregation pheromone in Blattella germanica.

Sex Pheromone of the French Black Cutworm Moth, Agrotis ipsilon (Lepidoptera: Noctuidae): Identification and Regulation of a Multicomponent Blend

The sex pheromone blend of a European strain of the black cutworm moth, Agrotis ipsilon (Hufnagel), was investigated. Chemical analyses of pheromone gland extracts from 4- to 8-day-old females showed that individual isolated glands contained only very small amounts of pheromone. High-resolution gas chromatography combined with mass spectrometry (GC–MS) analyses showed the presence of cis-7-dodecenyl acetate (Z7-12:Ac), cis-9-tetradecenyl acetate (Z9-14:Ac), cis-11-tetradecenyl acetate (Z11-14:Ac), cis-11-hexadecenyl acetate (Z11-16:Ac), and cis-11-hexadecenol (Z11-16:OH) in biologically active pheromone gland extracts. Removing 27-12: Ac, Z9-14:Ac, or Z11-16:Ac from the complete gland extract by GC trapping techniques strongly reduced the attractiveness of the pheromone blend tested in a wind tunnel. Lack of cis-5-decenyl acetate (Z5-10:Ac) or Z11-16:OH did not affect the blend attractiveness. Chemical and behavioral analyses showed that pheromone components are produced during photophase, at least 2 hr before lights off. Quantitative data showed that decapitation inhibited the production of Z7-12:Ac, Z9-14:Ac, Z11-14:Ac, Z11-16:Ac, and Z11-16:OH, but production in decapitated females was stimulated in response to injection of synthetic Heliothis zea PBAN (pheromone biosynthesis activating neuropeptide) or A. ipsilon brain–subesophageal (Br-SEG) homogenates. Moreover, upon injecting BR-SEG homogenates, other minor components were detected, which were tentatively identified as cis-8-dodecenyl actetate (Z8-12:Ac) and Z5-10:Ac. Our study demonstrated that Z11-l6:Ac is one of the main active components produced by the pheromone gland of this European population of A. ipsilon, in addition to Z7-12:Ac/Z9-14:Ac, which were investigated in a previous behavioral analysis. All these data strongly suggest that some polymorphism is present in pheromone communication in different strains of A. ipsilon.

Juvenile hormone stimulates pheromonotropic brain factor release in the female black cutworm, Agrotis ipsilon

Abstract Sex pheromone biosynthesis of various insects has been shown to be controlled by a brain neuropeptide (PBAN) and in some cases by juvenile hormone (JH) from the corpora allata (CA). However, the mode of action of JH in the control of sex pheromone biosynthesis is still unclear. Although pheromonotropic activity was detected in their brains, females of the black cutworm, Agrotis ipsilon , lacking CA did not produce sex pheromone. Pheromone production could be restored in allatectomized female moths by injection of brain extracts or by injection of synthetic PBAN or JH-III. Injection of synthetic JH-III did not stimulate pheromone production in decapitated females. These results indicate that JH secreted by CA control sex pheromone biosynthesis of A. ipsilon females by stimulating pheromonotropic brain factor (PBAN-like factor) release from the central nervous system and not by controlling PBAN-like production or by priming PBAN-like target glandular cells.

Cockroach mating behaviors, sex pheromones, and abdominal glands (Dictyoptera: Blaberidae)

Two chemical signals are essential in all cockroach sexual behavioral sequences: the sex pheromone released by one partner, generally the female (for long distance attraction), and an aphrodisiac sex pheromone produced exclusively by male tergal glands (for female mounting and tergal contact or “feeding” behavior). Unlike the other cockroach groups, the males of the Oxyhaloinae species produce both chemical signals: the pheromone and the aphrodisiac. The occurrence of three patterns of mating behavior (A, B, and C), the production of male sex pheromones, and the existence in the male of developed sternal and tergal glands in seven related Oxyhaloinae species, make these cockroaches a useful model for studying the evolution of mating behavior patterns. The various types of mating behavior were not classified in the previous studies by Roth and Barth. In this report, they have been named type A (female in upper position), B (male in upper position), and C (male and female end to end). In type A mating, the male tergal glands, which are licked by the females, are well developed, whereas in types B and C, there is no licking of the males tergal secretion by the females and the tergal glands are much less developed; the aphrodisiacs secreted by the tergal glands may no longer act in this case through contact chemoreception, but through an olfactory process involving volatile components. One common sex pheromone component seems to be acetoin. I suggest that the mating behavior tends from A toward B and C during the evolutionary process with a concomitant regression of the tergal glands and changes in the aphrodisiac emission levels. The mating behavioral sequences of cockroaches (Dictyoptera) and crickets (Orthoptera) show a striking degree of similarity and are probably examples of convergent evolution.

Cuticular Hydrocarbon Profiles of Dominant Versus Subordinate Male Nauphoeta cinerea Cockroaches

Interactions between male Nauphoeta cinerea cockroaches are characterized by an elaborate ritual that leads to a stable dominant–subordinate hierarchy between two individuals. Chemical signals involving volatile sex pheromones and cuticular hydrocarbons play an important role in establishing and maintaining dominance status. The present study was performed to identify cuticular hydrocarbons in two- and three-times dominant or subordinate individuals obtained by forcing dyadic encounters. Two methods, i.e., solid-phase microextraction (SPME) and organic solvent extraction, were used to isolate cuticular hydrocarbons. A total of 23 peaks of cuticular hydrocarbons were identified. Analysis showed quantitative differences in hydrocarbon profiles of three-times dominant and subordinate individuals according to extraction method and dominance status. Dominant individuals were characterized by higher proportions of the monomethylalkanes 11- and 13-MeC36, 13- and 15-MeC38, and 11-, 13-, and 15-MeC35, while subordinate individuals had higher proportions of the following monomethylalkanes: 7-, 9-, and 11-MeC31, 5-MeC31, 3- and 8-MeC32, and 9-, 10- , 11-, and 12-MeC32. Discussion focuses on the reliability of hydrocarbons as indicators of dominance status and on their correlation with physiological processes.

Chemical recognition of queen cells by honey bee workersApis mellifera (Hymenoptera: Apidae)

SummaryHoney bee workers are able to nurse or to destroy and thus to recognize the capped queen cells containing a pupa. Fatty acid esters, especially methyl oleate, methyl palmitate and ethyl oleate were found in significant amounts on the queen pupal cuticle. Methyl oleate, the major component, along with smaller amounts of methyl linoleate and methyl linolenate, were involved in the recognition of queen cells by workers. In natural conditions of the colony, queen cells containing a paraffin pupal lure with methyl oleate were accepted 5.9 days by workers, releasing about 1.8 queen pupa equivalents during that period, when control cells (without ester) were kept only 2.1 days. Although these esters are non specific to honey bees, they are of great importance in social regulation of the honey bee colony.

Sensory asymmetries in the olfactory system underlie sexual pheromone communication in the cockroach Nauphoeta cinerea

In most insect species, males process female sex pheromone information in specific macroglomeruli in the olfactory lobes of their brains. The purpose of this report is to present a novel system of pheromone perception. In Nauphoeta cinerea cockroaches, males produce sex pheromones that induce mating behavior in females but neither sex has macroglomeruli. In this study, we show that female N. cinerea show asymmetry in the number of glomeruli whereas males do not. Females have more glomeruli on the right side and amputation of the right antenna reduced female ability to find a male and mate whereas amputation of the left antenna did not. We show that a key factor in female mating behavior is perception of the male sex pheromone seducin by the right antenna and the asymmetrically organized deutocerebral glomeruli associated with it. In the symmetrical olfactory system of males the detection of seducin may be involved in establishing dominance hierarchies.