Developmental biology and seasonal phenology of Aacanthocnema dobsoni (Hemiptera: Triozidae) and the influence of climate-mediated changes in body size on vibrational signals

The biology and seasonal phenology of Aacanthocnema dobsoni (Froggatt) were studied at a single site in Victoria over a 2 year period between 2013 and 2015. This species is monophagous on the dioecious host, Allocasuarina verticillata (Lam.) L. Johnson (Casuarinaceae). Laboratory studies found that females attained reproductive maturity 24 h post-eclosion, lived for 28.6 +/- 2.8 (mean +/- SE) days and laid 182 +/- 23 (mean +/- SE) eggs each. Egg development was most rapid at 26 degrees C, ceased below 7 degrees C and above 33 degrees C; hatching required 188 degree-days. Nymphs could not be reared to adulthood on excised host branchlets maintained under controlled conditions, so no developmental data were obtained for these life stages. Seasonal phenology data revealed pronounced developmental asynchrony, i.e. with overlapping generations and multiple life stages occurring simultaneously. Three generations per year were observed, and there was no evidence of either developmental (egg and nymph) or reproductive diapause. A 4 day heat wave in January 2014 drastically reduced psyllid abundance at the study site and the size of the adults that eclosed from the surviving nymphs. These smaller adults produced substrate-borne vibrational signals with altered characteristics, i.e. with significantly higher intensities and power. The altered signals might have facilitated communication over longer distances and increased mate finding opportunities when populations were low. The abundance of adults had recovered to preheat wave levels 3 months after the heat wave. High fecundity, multivoltinism and effective mate attraction signalling are life history traits that may mitigate against localised extinction of populations as a consequence of extreme weather events.