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| Silver-spotted skipper caterpillar with brown head - Chris Barnhart |
As I am a retired gastroenterologist, Chris Barnhart knew he could hook me with
this video of his showing a caterpillar shooting out its frass. Many animals have special
ways of eliminating their fecal matter, called frass when produced by insects,
to reduce disease or avoid predators.
Epargyreus caterpillars simply go ballistic.
The common
Epargyreus species we see in Missouri is the silver-spotted skipper,
Epargyreus clarus.
They are regularly found throughout the warm months nectaring on a wide
variety of flowers. Its caterpillars feed on a wide variety of plants
in the pea family, ranging from the beggar's ticks (tick trefoil) that
cling to your clothes to the black locust tree that can exceed 100 feet
tall.
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| Cocked and ready to fire |
Our silver-spotted skipper can use its
anal comb
to shoot its frass "faster than a scat out of hell," to quote Chris.
It can fly up to an astounding 38 body lengths away. (Yes, some one
actually has measured its record launch - and you thought filming it was
odd). It is not alone in long-range bombing. There are videos on line
of frass-flinging Asian caterpillars like these of
Mycalesis mineus,
Ypthima pandocus and.....oh well, you get the picture.
Frass flinging is commonly found among caterpillars that live in leaf
nests. Why do they bother? This is felt to be a defensive mechanism to
eliminate the smell in the nest which would be a clue to predators,
specifically the northern paper wasp,
Polistes fuscatus as described in
this study.
More stories of scat disposal and frass chain building caterpillars in future blogs.
