Insects

Oil palm (Elaeis guineensis Jacq.) production in Côte d’Ivoire depends on insect-mediated pollination by Elaeidobius weevils. From October 2011 to November 2013, we monitored 432 female inflorescences in three major production zones (La Mé, Grand Béréby, and Iboké). Each month, visits by E. kamerunicus, E. plagiatus, E. singularis, and E. subvittatus were recorded on the day of full anthesis during three discrete time periods (09:00–10:00, 11:00–12:00, and 16:00–17:00). Temperature and relative humidity were measured concurrently. Visitation peaked at 11:00 across sites, with abundance ~4-fold higher than at 09:00 and ~20-fold higher than at 16:00; mixed-model results indicated that this temporal pattern was consistent among sites (non-significant Site × Time interaction). E. subvittatus dominated visits to female inflorescences (71–74% of individuals), whereas E. kamerunicus showed lower visitation rates. Pollinator abundance was positively correlated with temperature (ρ = 0.18) and negatively correlated with relative humidity (ρ = −0.13), although these relationships were weak. These results identify late morning as a key activity period within the observation windows and suggest that adjusting field practices (e.g., insecticide timing) may reduce non-target impacts on pollinators.

Lipophorin receptors play a crucial role in the reproductive development of insects. However, their regulatory function in insect reproductive diapause remains poorly understood. In this study, a lipophorin receptor gene (GdLpR) was cloned from Galeruca daurica using RT-PCR. The open reading frame (ORF) of GdLpR is 2589 bp in length, encoding 862 amino acids, and possesses typical structural characteristics of the lipophorin receptor family. RT-qPCR analysis indicated that the expression of GdLpR is up-regulated in G. daurica adults before diapause, exhibits an expression pattern of initial down-regulation, subsequent up-regulation, and then further down-regulation during diapause, and is up-regulated again after diapause termination. After RNA interference of GdLpR, the expression levels of diapause-related genes ecdysone receptor (EcR), nuclear hormone receptor (HR3), and vitellogenin (Vg) were downregulated, while the expression level of fatty acid synthase (FAS) and total lipid content were upregulated, leading to premature diapause in adult G. daurica. These results indicate that GdLpR is involved in the regulation of reproductive diapause in G. daurica.

The bean bug Riptortus pedestris is one of the principal soybean pests throughout East Asia. Males release an aggregation pheromone consisting of three compounds—(E)-2-hexenyl (Z)-3-hexenoate (E2HZ3H), (E)-2-hexenyl (E)-2-hexenoate (E2HE2H) and myristyl isobutyrate (MI)—in a ratio of 1:5:1. Although pheromone-based baits have been extensively deployed to control the pest for the past three decades, the glands responsible for producing these volatiles have remained unidentified. Our investigations revealed that the metathoracic glands (MTGs) of males synthesized the two pheromonal esters, E2HZ3H and E2HE2H, along with a suite of auxiliary compounds: (E)-2-hexenal, hexanoic acid, (E)-3-hexenoic acid, (E)-2-hexenoic acid, (E)-2-octenal, and (E)-2-hexenyl hexanoate (E2HH). Female MTGs were morphologically similar to those of males and generated the same auxiliary compounds, but lacked the capacity to produce the pheromonal esters E2HZ3H and E2HE2H. MI was released exclusively from the male abdominal sternites. Its quantity was nearly uniform across all sternal segments, implying secretion from an epidermal glandular patch (GP) that was evenly distributed over the sternites. In nymphs, dorsal abdominal glands (DAGs) emitted several volatiles—including (E)-2-hexenal, 4-oxo-(E)-2-hexenal, (E)-2-octenal, and (E)-2-octenoic acid—some of which are characteristic defensive compounds of heteropterans. Thus, our study clarifies how sex- and stage-specific glands contribute to the chemical polymorphism observed in R. pedestris.