Master of suspense

[Kenelm Philip]

	I've gotten a number of queries re my posting about _Pieris rapae_
larvae living in the human gut. Most wanted to know my source for this
tidbit, and many found it hard to believe that the caterpillars survived
passing through the stomach. One objected to the phrase "living in the
human gut", and said it should have read "_on_".

	So, here's the source: "Six-Legged Science" by Brian Hocking (1968),
p. 101. Here is the quote in its entirety:

"I should perhaps mention at this point that there is an uncommon condition,
referred to in medical jargon as scoleciasis, in which the human gut houses
living caterpillars. The term scoleciasis should properly be restricted to
an infestation with tapeworms, but that no other term has been coined for
this other condition serves to emphasize that it is not common. Interest-
ingly, the commonest caterpillar involved is our friend the imported cabbage
worm, taking up residence presumably when its host eats raw or undercooked
cabbage, and maintained by his continuing to do so in uncommon amounts. So
perhaps it is well to notice tiny white pillars [eggs]--or tiny green
caterpillars--on cabbage leaves, and give them an extra chew in passing.
So far as I know, these caterpillars never mature on the lee side of the
stomach or on the wall of the large intestine, so that the expression
'butterflies in the stomach' remains no more than a metaphor, at least as
regards living ones."

	For the people who thought the caterpillars could never survive
going through the stomach and its acids, note that there is a well-known
condition, called myiasis, in which live maggots reside within the body.
Intestinal myiasis is one form that this can take, and Evens (in "Life on
a Little-known Planet") notes that "A wide variety of fly larvae, including
some otherwise relatively harmless ones, are able to establish infections in
the digestive tract if swallowed." As involves stomach acids, Evens states:
"The maggots of some of the myiasis producers are remarkably tough. Pro-
fessor James reports that some have been kept in 95 per cent alochol for
an hour and have been known to produce adults; they will also survive for
some time in hydrochloric acid, turpentine, or carbolic acid.

	And after all, tapeworm eggs manage to make the journey unscathed.

							Ken Philip



 
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