Largest parasitic insect

The largest parasitic insect is Scheffer's giant flea Hystrichopsylla schefferi, which was originally described from a single specimen taken from the nest of a mountain beaver Aplodontia rufa – a peculiar species of North American rodent inappropriately referred to as the mountain beaver, as it is neither a mountain-dweller nor a beaver – at Puyallup, Washington, USA, in 1913. Female specimens of this giant flea have been measured up to 13 mm long – more than the diameter of a pencil. In comparison, the common flea Pulex irritans has an average length of only 1.0–2.5 mm.

Despite being such a sizeable creature in flea terms, until as recently as June 2014 this species was not represented by a single photograph of a living confirmed specimen. During that month, however, Dr Merrill Peterson, curator of the insect collection at Western Washington University, USA, and his wife Carol trapped a live mountain beaver in the wild and procured from its fur a living Scheffer's giant flea that was duly photographed.