Sexual Dimorphism, Diel Activity, and Mating Behavior of Eubulus cf. elongatus: an Emergent Pest Root in Cassava Crops.

Eubulus cf. elongatus Hustache (Coleoptera: Curculionidae) is a Neotropical species recently considered an important pest of cassava (Manihot esculenta Crantz) in Brazil. This weevil feeds on cassava roots under the soil, which makes detection and control by traditional methods as pesticide quite ineffective. Besides that, no information is available about morphology, sex identification, and behavior. Given its recent category as a pest, its morphology, sex identification, and behavior were previously unknown. Laboratory reared adults of E. cf. elongatus emerged from pupal chambers originated from Embrapa Cerrados (Planaltina, Federal District, Brazil) were used to investigate sexual dimorphism, sex ratio, diel activity, and mating behavior. The visible sexual dimorphism was observed in the hind tibiae of females, which presents a more expansive distal portion than a proximal portion. The sex ratio analysis of E. cf. elongatus evidenced a proportion of males and females, approximately 1:1 in 2018, while 1.5:1, both similar to other species of curculionids. Males and females show predominantly nocturnal activity, including the mating attempts during scotophase. Three distinct phases of mating behavior developed by E. cf. elongatus are described: (i) pre-copulation, (ii) copulation, and (iii) post-copulation. The results obtained in this study provide essential information for developing monitoring and control strategies within an integrated management program for this critical pest species in cassava crops in Brazil.

Identification of Zingiberenol and Murgantiol as Components of the Aggregation-Sex Pheromone of the Rice Stink Bug, Mormidea v-luteum (Heteroptera: Pentatomidae).

Mormidea v-luteum (Lichtenstein, 1796) feeds on commercial crops, such as rice and ryegrass, causing damage that slows growth and reduces productivity. With the aim of developing an eco-friendly control technique, we investigated the compounds involved in chemical communication in this species. The volatiles produced by a group of seven males or females allocated to different aerated glass chambers were collected for 24 h and analyzed by gas chromatograph/mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy. The analyses showed six male-specific compounds, identified as two isomers of zingiberenol (compounds 1 and 2), three isomers of murgantiol (3, 5 and 6) and sesquipiperitol (4). Compounds 1 and 5 were the major components and were produced in a ratio of 6:4. The absolute stereochemistry of the two isomers of zingiberenol was established as (1S,4R,1'S)-1 and (1R,4R,1'S)-2 by chiral gas chromatography. Stereochemistry was not determined for all the other molecules. To confirm the attractiveness of these chemicals, bioassays were performed in a Y-tube olfactometer, first using crude extracts and, subsequently, synthetic compounds. Male volatiles were attractive to both sexes, demonstrating an aggregation pheromone. In bioassays with synthetic compounds, (1'S)-zingiberenol was highly attractive to both males and females. However, when (1'S)-murgantiol was tested, only females were attracted. Interestingly, when a mixture of zingiberenol and murgantiol isomers was tested, it was attractive to both sexes, with females more attracted to the mixture than to zingiberenol alone; males did not distinguish between treatments. Thus, the bioassay data suggest that the molecules have different functions in chemical communication of this species: zingiberenol acts primarily as an aggregation pheromone, while murgantiol plays a role as a sex pheromone.

Camphor and Borneol as the Male-Produced Sex Pheromone of the Shield Bug, Orsilochides leucoptera (Hemiptera: Scutelleridae).

The ability of stink bugs to release high amounts of strong-smelling and irritating defensive compounds is related to their metathoracic gland (MTG), which is an exocrine gland with defensive, sexual, alarm and aggregation signal functions. Orsilochides leucoptera (Scutelleridae) is a widespread species in the Neotropical region that feeds on plants of the families Malvaceae, Poaceae and Euphorbiaceae. A series of compounds (ketones, alcohols and esters) have been identified in the MTGs among the three species of Scutelleridae whose MTG secretions have been investigated thus far; however, no sex pheromone compounds have been described for any scutellerid species. The aim of this work was to study sex pheromone communication within this family of stink bugs, and identify the compounds present in the MTG of O. leucoptera. Analysis by gas chromatography/mass spectrometry (GC/MS) revealed two male specific compounds identified as (R)-camphor (1) and (R)-borneol (2), which were attractive to females in Y-tube olfactometer bioassays. Also, GC/MS analysis of secretions from MTG of males and females of O. leucoptera, identified eight additional compounds: 2-(E)-hexenal (3), (E)-4-oxo-2-hexenal (4), (E)-hex-2-enyl acetate (5), (R)-linalool (6), (R)-α-terpineol (7), dodecane (8), 1-tridecene (9) and n-tridecane (10). From these, (R)-α-terpineol was detected only in the gland of males, and is probably a biosynthetic intermediate of the pheromone components. Most of the MTG compounds identified in O. leucoptera have been identified in other heteropteran species. Camphor is often a toxic and repellent compound for insects. However, we report it, for the first time, as a sex pheromone component of an insect.