Archaeologists excavating a ca. 30 m2 stable associated with Hadrian’s Wall in England (Roman, ca. 100 AD) found more than 250,000 puparia of the stable fly (Stomoxys calcitrans). Subsequently it was discovered that most of the larvae had pupated prematurely, before reaching full developmental maturity. The most likely cause of this phenomenon is that bracken was a major component of the plant litter used to line the floors of such structures, a testament to the efficacy of the insecticidal ecdysomes in the bracken. For a fascinating narrative on this situation and other aspects of bracken toxicology, see Robbin Moran’s (2004) excellent book, A Natural History of Ferns.
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