r.d.j.butcher at dundee.ac.uk
Mon Jan 11 04:18:23 EST 1999
> Do caterpillars have a gender?
Yes. Either male or Female.
Most species of lepidoptera are sexual, and thus they exist in two
forms, male or female. However, examples of parthenogenesis exist in
which only females exist. Hermaphrodites (both male and female
functions in the same organism) are not known in lepidoptera (moths
> caterpillars turn into female butterflies/moths, or are they gender-
> neutral - and perhaps have some clever means of determining if
> ButterflyWorld needs more males or females at that time, and
> become whatever is needed?
Males become males, females likewise only females.
Sex is determined early after egg fertilisation in a manner
simplistically similar to mammals like us except that females are
heterogametric (W/Z) and males arent (In mammals it is the male that
is heterogametric..X/Y and females carry only the Y chromosome).
Therefore, female caterpillars will develop into female
moths/butterflies, and males likewise into males.
Their is no known ability to sex change (e.g .females become males as
in say some fish) in response to a skewed sex ratio in the local
population). Neither is their any known naturall;y evolved
environmental sex determination (e.g. temperature during development
affects sex, such as in many reptilians like crocodiles), but see
below under exceptions.
However, two sorts of exceptions, albeit relatively rare, are known.
(1) gynadromorph / intersexes. (Fairly common in cultured lepidoptera
of some species, but less common in the "wild").
Here a "female" butterfly/moth will have some morphology of a "male"
or visa versa. This is not a hermaphrodite. What happens is that
after initial sex determination at fertilisation determined by master
gene(s) on the sex chromosomes in some cells either factor(s) act to
inhibit the sex determination cascade down stream of the sex genes
and so these cells develop as the opposite sex (giving a mosaic
pattern according to the cells that are affected and at what point
during development). This is analagous to the effect of antibarnacle
paints on the sex of many marine crustaceans you may have heard
about, or the PBD? in PVC food wrappings in humans etc). Another is
that as the fertilised egg commited to female development (WZ)
divides to form all the cells that will constitute the organism, in
rare cases one of the sex chromosomes is "lost" (non-dysjunction) and
so all the cells derived from this, now carrying only the W
chromosome, will be committed to being male. Again the mosaicism seen
depends upon when the dysjunction happened in the cellular
differentitaion / replication phase of development.
Genetically determined males are modified to develop as females.
Usually the caterpilla and adult will appear as a female and so
this will go unnoticed. Indeed only molecular genetics will allow
you to see that the female is indeed genetically determined as a
male!! However, If this is not complete in all tissues (e.g. the
bacteria is not in all tissue..see below), mosaic gynandromorphs will
It has recently been shown that in the asian corn borer moth
(sorry, cant remember the latin name at present) that a bacteria from
the Wolbachia pipientis subgenera, a group of intracellular parasites
that are widespread in insects, cause genetically determined males to
develop as females. the site of action is unknown, as is the
frequency of this across all lepidoptera.
Hope this answers your questions, but ask if not
Evolutionary and Ecological Entomology Unit,
Department of Biological Sciences,
Dundee, DD1 4HN,
Work Phone:- 01382-344291 (Office), 01382-344756 (Lab).
e-mail:- r.d.j.butcher at dundee.ac.uk
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