California’s Butterflies

Diapause Methods

Butterflies exhibit a number of ways to diapause.  Some butterfly species diapause in the egg stage, which is usually a fully formed larva inside an egg.  In this case the larva simply waits until diapause is broken and then hatches.  In some cases this diapause is broken after a three or four month cold period.  Immediately after hatching the young larva searches for food and begins feeding.

 

Another method of diapause is as a larva.  In some species this can be rather plastic and can occur at any larval instar (intermediate stage between molting), but in most butterflies this occurs at some specific larval instar.  The Fritillaries all diapause as first instars that immediately enter diapause after hatching from the egg.  Many blues go into diapause in either the second or third instar.  The coppers that diapause as larvae enter an obligate diapause as second instars.  Some of these butterflies such as checkerspots can re-enter diapause many times to survive through long periods of drought or cold in alpine or arctic conditions.

 

Another type of diapause is as a mature larva.  In this case the larva is diapausing just prior to pupation.  When diapause is broken the larva does not feed again, but immediately pupates.  The larva may drink but never feeds again.  The yucca moth is an example of this type of diapause and interestingly can diapause for over 20 years without feeding.  The tailed blues also exhibit this type of diapause.  Many skippers also diapause as mature larvae.

 

A fourth type of diapause is as a pupa.  True pupal diapause is as an unformed pupa.  In this case when you open up the chrysalis all you find is a bag of fluid with imaginal disks.  With other species that diapause as pupae, it is really as a pharate adult, or an adult that is nearly completely developed.  Species that diapause as pupae are the Glaucopsyche section of blues, such as the Euphilotes, Philotiella, Philotes, and Glaucopsyche genera.

 

A fifth type of diapause is as a pharate adult inside a chrysalis.  There are many species that diapause in this stage.  In fact, most of the swallowtails, many hairstreaks, and many Pierids enter diapause in this stage.

 

The final method of diapause is as an adult.  Many Nymphalids enter diapause as adults.  Those species that migrate south in the fall and north in the spring enter diapause as adults.