Tuesday, April 20, 2021

Carpet Beetle


Barb found a tiny dark spot on her comb in our cabin.  It measured almost 1/10" (2.5mm) and under high magnification, to our surprise, it wasn't a tick.  INaturalist quickly identified it as a common carpet beetle, Anthraenus verbasci.  Their larvae feed on keratin and chitin in natural fibers like dead insects, animal hair and feathers so it must have been there for hair.

Carpet Beetle, aka A. verbasci - Wikipedia

That would have been the end of the story except for some interesting details in its lifecycle.  For starters, it is the first insect proven to have its lifecycle adjusted by temperature.  Both its incubation and pupation is 5 times longer with lower temperatures.  The adults live for 2 weeks, feeding on nectar and pollen while mating and laying their eggs in human habitation and bird nests.  The larvae then feed on natural fibers in houses, bird nests, and in museums where they can be a serious pest.

Woolly Bear, aka A. verbasci  -  Wikipedia
Head-on view - Wikipedia

The larvae are densely covered in large setae (hairs), and are commonly called "wooly bears" like our moth larvae.  These are defensive against its parasitoid predatory wasp, Laelius pedatus.  The female wasp will land on it and attempt to paralyze it with its stinger-like ovipositor.  The hairs will stick to the wasp, an annoying deterrence which rarely prevents the wasp from winning.  



Laelius pedatus - only 2 mm long - Tom Murray CC

It will then observe the larva for up to 24 hours, repeatedly biting it to assure paralysis while removing the irritating hairs from its body before inserting its egg into the helpless victim.  The egg hatches and a week later the wasp larva will have consumed the woolly bear and formed a pupa.

Carpet beetles are considered a major pest in English museums, often destroying insect collections.  Their most likely entrance is from nearby nests of the same English Sparrows which have achieved a pest status here in the US.  Poetic justice, anyone?