Bernhard Weissbecker

Insect antenna as a smoke detector

The larvae of jewel beetles of the genus Melanophila (Buprestidae) can develop only in the wood of trees freshly killed by fire. To arrange this, the beetles need to approach forest fires from as far as 50 kilometres away, . They are the only buprestid beetles known to have paired thoracic pit organs, which behavioural, ultrastructural and physiological experiments have shown to be highly sensitive infrared receptors, useful for detecting forest fires. It has been suggested that Melanophila can sense the smoke from fires, but behavioural experiments failed to show that crawling beetles approach smoke sources. We find that the antennae of jewel beetles can detect substances emitted in smoke from burning wood.

Volatile Emissions from Aesculus hippocastanum Induced by Mining of Larval Stages of Cameraria ohridella Influence Oviposition by Conspecific Females

Larval stages of the horse chestnut leafminer Cameraria ohridella can completely destroy the surface of horse chestnut leaves, Aesculus hippocastanum. This study investigated the effect of the degree of leaf browning caused by the insect’s larvae on olfactory detection, aggregation, and oviposition of C. ohridella adults. The influence of A. hippocastanum flower scent on oviposition of the first generation was also evaluated. Utilizing gas chromatography coupled with parallel detection by mass spectrometry and electroantennography (GC-MS/EAD), more than 30 compounds eliciting responses from antennae of C. ohridella were detected. Oviposition and mining by C. ohridella caused significant changes in the profile of leaf volatiles of A. hippocastanum. After oviposition and subsequent mining by early larval stages (L1–L3), substances such as benzaldehyde, 1,8-cineole, benzyl alcohol, 2-phenylethanol, methyl salicylate, (E)-β-caryophyllene, and (E,E)-α-farnesene were emitted in addition to the compounds emitted by uninfested leaves. Insects were able to detect these compounds. The emitted amount of these substances increased with progressive larval development. During late larval stages (L4, L5) and severe loss of green leaf area, (E,E)-2,4-hexadienal, (E/Z)-linalool oxide (furanoid), nonanal, and decanal were also released by leaves. These alterations of the profile of volatiles caused modifications in aggregation of C. ohridella on leaves. In choice tests, leaves in early infestation stages showed no significant effect on aggregation, whereas insects avoided leaves in late infestation stages. Further choice tests with leaves treated with single compounds led to the identification of substances mediating an increase or decrease in oviposition.