Life Cycle

Illustration of the Life Cycle of the Marsh Fritillary Butterfly.

All butterflies and moths (lepidoptera) have a four stage life cycle. The stages are: egg, larva or caterpillar, pupa or chrysalis and finally the adult butterfly or moth. Most Irish butterflies take a full year to complete their life cycle while others can fit two or more broods or generations during a full year. The larvae of some species live alone while other species larvae live in groups. Here is the illustrated life cycle of one of our rarer butterflies, the Marsh Fritillary.

The Marsh Fritillary takes a year to complete its life cycle. The larva of this butterfly moults five times. Each inter-moult stage is called an instar. The first instar is the larval stage before the first moult. The second instar is the larval stage following the first moult but before the second moult. The skin of a larva stretches as the larva grows but a point is reached when the larva must moult or shed its skin in order to grow further.  In some species, the larval skin has a different appearance following a moult  which  allows the larva to be aged.

Below we show all six instars of the Marsh Fritillary larva. Please note that while dates are provided for each photograph, in warm, sunny springs development is faster and the final instar is reached earlier.

Marsh Fritillary eggs are laid in May/June on the underside of a leaf of the caterpillar’s food plant, the Devil’s-bit Scabious. Eggs are laid in large batches. This clump contains around 300 eggs. Its eggs can take about 30 days or longer to hatch, depending on the nature of the site and weather conditions. This photograph was taken on 19 June 2013.©J.Harding.

First instar larvae soon after hatching in late July. These feed and live communally inside a protective web formed by the larvae drawing the leaves of the food plant together. This photograph was taken on 24 July 2017.©J.Harding.

These second instar larvae are  spinning a new web around part of the food plant. This photograph was taken on 31 July 2017 .©J.Harding.

Third instar larvae from 22 September 2017. These  are darker than the  earlier stages. These larvae will soon spin a denser web concealed under the vegetation in which to pass the winter, protected against the harsh weather. Within this web, before winter arrives, they will moult for the third time to enter the fourth instar. ©J.Harding..

These are fourth  instar Marsh Fritillary larvae after hibernation .   This photo was taken on 14 March 2015. They still form a web which is now used as a basking platform. As you can see, these are now black in colour. The darker colour enables the larvae to heat up more efficiently in the bright  sunlight but cool air temperatures in February and March.The larvae are basking together in order to increase their body temperature in order to digest their food.  ©J.Harding..

Fifth instar larvae are black with white speckling. The fifth instar larvae live exposed on the vegetation and do not form a web.  At night and during unsuitable weather the larvae retreat under vegetation.These feed in smaller  and looser groups as the nest begins to break up. This photograph of recently moulted larvae was taken on 7 April 2018. ©J.Harding.

A sixth instar Marsh Fritillary larva. Mature larvae feed independently. This one is fully grown and is ready to form a pupa [chrysalis] in which it will undergo metamorphosis [change its shape] to become an adult butterfly. It is ready to pupate in late April-mid-May..This was taken on  12 April 2017 .©J.Harding.

This is a Marsh Fritillary pupa. It is attached to a leaf by a silken pad spun by the larva. The pupa is usually better concealed than this one but is occasionally found on different colour surfaces. This is not untypical of species that are distasteful to birds.  This photograph was taken on 4 May 2013.©J.Harding.

Here is a freshly emerged male Marsh Fritillary. The sexes look similar but the female is larger. The butterfly is ready to mate to start the life cycle process again. The female butterfly often mates and lays eggs on the day she emerges from her chrysalis. This photograph was taken on 28 May 2017.©J.Harding.