Function of tibial spurs?

[Pierre Zagatti]

In article <338469D6.7DD3 at unm.edu>, "Paul J. Watson" <pwatson at unm.edu>
says:
>
>Hello! I am conducting a little behavioral study of the mating system of
>an apparently new species of Adelid "fairy moth" in NW Montana (genus
>Adela). Both sexes have long sharp tibial spurs (0,2,4). Can anyone tell
>me the ecological function of these spurs in leps in general and, if
>possible, in fairy moths in particular? References would be greatly
>appreciated.
>
>Thank you very much,
>
>Paul J. Watson
>University of New Mexico
>pwatson at unm.edu
>http://biology001.unm.edu/~pwatson/pjw_cv.htm

In many insects, the tibial spurs on forelegs are used
to clean the antennae. There is sometimes a specialized organ, as
in the ground beetles (Caraboidea). Now your Adelid does not seem
to have spurs on forelegs (0,2,4 ?)...
Another role we found for these spurs was sexual. In one species
(Cryptophlebia leucotreta, Tortricidae) there is a strong sexual
dimorphism, the male spurs on hindlegs bear androconia and are used
during courtship. The male place his hooked spurs on the female's
head so that the hooks just fit the base of female antennae !
But this is only a short sequence of a rather complex courtship
behavior (Zagatti & Castel, 1987, Ann. Soc. entomol. France,
23: 113-123).

Now help yourself to find the role of these spurs in Adela. I think
that spurs belong to the "ancestral insect leg", i.e. nearly all
orders show these spurs. Then secondary evolutions may lead to
specialization for these organs for cleaning, burrowing or mating.
Frequently they totally or partially disappear, which character is
used by systematics in higher level diagnoses (see subfamilies of
Noctuids for example).

Hope this helps


Pierre Zagatti
INRA Phytopharmacie et Mediateurs Chimiques
78026 Versailles Cedex
France
zagatti at versailles.inra.fr
http://www.jouy.inra.fr/papillon/