Source: Bunches of butterflies
These aggregations of puddling butterflies usually consist largely of males, which are thought to be replenishing their sodium-reserves, lost (or soon to be lost) in the process of delivering a spermatophore to females during mating. Or more prosaically, it may be to enable the males to produce a ‘nuptial gift’ in the form of sodium, for the females.
I am a retired entomologist with a background in quarantine pests and invasive invertebrates. I studied zoology at Imperial College (University of London) and did a PhD on the population dynamics of a cereal aphid (Metopolophium dirhodum) in the UK. I spent 5 years with the British Antarctic Survey studing cold hardiness of Antarctic invertebates and 17 years with the Food and Environment Research Agency. My main interests now are natural history, photography, painting and bird watching.