Monarch Mating

Maurice O'Donnell OdonnellM at
Thu Feb 24 22:32:13 EST 2000

I would agree with the comment about the apparent brutality of monarch mating behaviour.  A week or so ago, in my own garden, I observed a male vigorously chase a female in the air.  He was very close behind her but not connected.  The female was forced to the ground.  Then, as the female was not aligned correctly, she was tossed around to allow mating to occur, which was very brief.  The mating took place almost at my feet so I was in a good position to observe!
I also recently observed a yellow admiral (Bassaris itea: Nymphalidae) chase a monarch off the property.  The monarch returned and was chased off a second time.  The yellow admiral would be perhaps a third of the size of the monarch and the event seemed a little odd.

Maurice O'Donnell
National Plant Pest Reference Laboratory
Ministry of Agriculture & Forestry
PO Box 24
New Zealand
phone 64-3-325-3921
fax 64-3-325-3909
email odonnellm at

>>> Paul Cherubini <cherubini at> 25/02/2000 16:10:31 >>>
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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