«Love is in the Air» Identification of the putative sex pheromone of four-spot ladybird, Harmonia quadripunctata

The first sex pheromone in a lady beetle species has been identified recently in the Asian lady
beetle, Harmonia axyridis (Coleoptera, Coccinellidae). In the presence of aphid prey, mature
females exhibit a stereotyped calling behavior that leads to the emission of a mixture of five
terpenes that is attractive to males and induces copulation. While the calling behavior has
already been observed in several coccinellids, the presence of similar pheromonal
communication in other coccinellid species has not been studied.
To assess the conservation of chemical communication mechanisms within the genus, in this
study, we investigated the potential emission of a sexual pheromone in Harmonia
quadripunctata.
H. quadripunctata individuals were collected in the field and reared under laboratory
conditions. Their offspring larvae were fed aphids ad libitum throughout their development.
Prior to reaching sexual maturity, adults were separated by sex. Adults were maintained on a
diet of sugar lumps and multiflower pollen for the first six days post-emergence, followed by
aphids ad libitum.
Volatile organic compounds (VOCs) emitted by adults were sampled after 15 and 20 days, with
fifteen replicates per sex and age group. VOCs emitted were collected using dynamic headspace
sampling and analyzed by TD-GC-MS. At 15 days, no significant differences in VOC profiles
between males and females were observed. However, at 20 days, three compounds—β
caryophyllene, β-elemene, and α-humulene—were detected exclusively in females. These
compounds are common with the H. axyridis sexual pheromone.
These results suggest that H. quadripunctata females may emit a sex pheromone similar to that
of H. axyridis, indicating a potential conserved chemical communication mechanism within the
genus. Further behavioral assays are necessary to confirm the functional role of these
compounds in mate attraction. This study contributes to our understanding of sexual
communication in coccinellids and may inform future phylogenetic analyses within this family.