Monarch Mating

Paul Cherubini cherubini at
Thu Feb 24 14:01:06 EST 2000

Sally wrote:
> I have been watching monarchs mate and I have some questions. In what other
> species of butterflies do the males carry the females in flight connected by
> genitalia? How would you describe the opening in which the male and female
> genitalia are located? How would you describe anatomically the process
> whereby the male and female grasp each other during mating? 

The reference below (available at the UC Berkeley library) covers
monarch mating very well. Sex pheromones (odors) do not seem to be
involved in monarch mating or sex descrimination as they are in the
Queen butterfly.Male monarchs grab females with their legs in 
flight and the pair floats to the ground.Unlike the female Queen butterfly,
the female monarch is nearly always resisting and some interpret
this (in human terms) as essentially rape.

Females mate several times in their lives and produce 300-700 eggs. 
The eggs don't all mature at once and apparently the sperm from the 
most recent mating only fertilizes the eggs that mature 
until the next mating. So the eggs from a single
female will ultimately have been fertilizedby several different males 
during the course of her 1-2 month reproductive life (after reproductive
diapause ends in February).

Since males do not seem to be able to distinguish other males on the basis 
of odor it is common to see male monarchs chasing and grabbing one
another in flight and struggling to mate with one another on the ground.
Scientists sometimes call this homocourtship.

Pliske, T. E. 1975. Courtship behaviour of the Monarch butterfly, Danaus
plexippus L. Annals of the Entomological Society of America 68:143-151

Many more references about monarch reproduction can be found at

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