The role of sex pheromones in a sexually cannibalistic praying mantid, Pseudomantis albofimbriata: identification and behavioural responses

Praying mantids are a group of charismatic predatory insects that use visual cues for mate location at short-distances, whereas long-distance communication mainly relies on chemical cues, i.e., air-borne pheromone s. Pheromones have been assumed to be important components of the mantid mating system. This thesis examines the pheromone biology in the false garden mantid, Pseudomantis albofimbriata Stål which is a sit-and-wait predator, sexually cannibalistic and size dimorphic, mainly found in eastern Australia. Various aspects of mating system and reproductive biology have previously been investigated in P. albofimbriata, however direct evidence of female-emitted pheromones and their chemical identification is lacking. Before starting the chemical identification, I investigated the female calling behaviour and male responses. This behavioural study described female cal ling behaviour i n this species for the first time and provided evidence that female calling behaviour and pheromone emission are intimately linked. Furthermore, the observations indicated the age and time window in which volatile pheromone collection would be most successful fo r P. albofimbriata. In addition, I made an attempt to identify the pheromone emission site in females and proposed that sex pheromone glands could be present on the intertergal membrane between the abdominal segments 3/4, 4/5, 5/6 and 6/7 on the female, however glandular tissue has not been found. The distribution and abundance of olfactory sensilla in males using scanning electron microscopy (SEM), which responsible for volatile chemical signal detection has also described. Then, the collection of volatiles from false garden mantids was conducted using three different methods - air trapping, solid-phase microextraction (SPME) and solvent extraction - to identify the suitable volatile collection method. The samples collected analysed through the gas chromatography linked to mass spectrometry (GC-MS). The results indicated that solvent extraction and air trapping met hods identified a series of hydrocarbons, mainly alkanes, in praying mantid volatiles that is present in both male and female samples, suggesting these methods were unable to identify female-specific compounds that might be candidates for pheromones. However, the SPME method successfully identified three acidic compounds such as tetradecanoic acid (C 14 ), pentadecanoic acid (C 15 ), n -hexadecanoic acid (C 16 ), that were female-specific. Then, I repeated the SPME method with slight modifications to identify the pheromone from female and similar results obtained indicate the se compounds probable pheromone candidates in P. albofimbriata. I subsequently conducted behavioural assay to test male responses to these chemicals. Males were not significantly attracted to the synthetic samples of C 14 , C 15 and C 16 acid compounds, demonstrating these compounds were unlikely to be sex pheromone components for this species, requiring further work on identifying additional chemicals in the female profiles. On the whole, this thesis makes a contribution to understanding the chemical ecology in praying mantid mating systems.