Ever wonder if there’s a name for that particular smell that happens when it rains on hot dry dust? Well, there is – it’s petrichor.
According to the Oxford Dictionary, its origins are:
Wikipedia gives more:
The term was coined in 1964 by two Australian researchers, Bear and Thomas, for an article in the journal Nature.In the article, the authors describe how the smell derives from an oil exuded by certain plants during dry periods, whereupon it is absorbed by clay-based soils and rocks. During rain, the oil is released into the air along with another compound, geosmin, a metabolic by-product of certain Actinobacteria, which is emitted by wet soil, producing the distinctive scent; ozone may also be present if there is lightning. In a follow-up paper, Bear and Thomas (1965) showed that the oil retards seed germination and early plant growth. This would indicate that the plants exude the oil in order to safeguard the seeds from germination under duress.
We smelt it the other day, after a long time without rain. Lismore has had the driest summer in 115 years – the wet season just failed to materialise. Instead of the 100-300 mL we usually get in January and February, it’s been 55 and 34. It feels wrong, and I have to say that I’ve enjoyed a (relatively) less humid summer, but not the hot temperatures that sometimes came with it.
A charming visitor appeared last week. According to both the Australian Museum and the Queensland Museum, it’s a female Lyraphora obliquata. Not much is known about the habits or biology of this species.
The colourful bug below was photographed by a neighbour (the graininess is because it’s from an iPhone). It’s the nymph of the eucalyptus tip-wilter bug, Amorbus alternatus.
Brisbane Insects has photos of both the adult eucalyptus tip-wilter bugs and nymphs.
As you know, insects go through many stages before reaching the adult form, and these instars look nothing like the adult or, often, each other. All fun and games for the hapless insect identifier.