Index

NOTE:   This material is incomplete research which emphasises  species and places in the Canberra region.

Biology of Butterflies and Moths

History of study in Australia

The first butterflies to be collected in Australia were those taken in 1770 by Banks and Solander, the naturalists on the Endeavour with Captain Cook.  The study of Australian butterflies and moths however has been very limited compared with the work undertaken on Northern Hemisphere species.  For example, only half of the Australian species of moths have been scientifically named.
 

Butterfly or Moth?

• butterflies are brightly coloured and active by day, while moths fly by night
• butterflies tend to rest with their wings held together above their backs, while moths tend to fold their wings like a roof over their backs
• up close, butterflies have clubbed tips to their antennae, while most moths have feathered antennae.

Reproduction

After hatching, larvae usually outgrow their skin and moult it four or five times, each time called an instar.  Larvae have hard heads and big jaws and may consume over twenty times their dry weight in plant food.

The pupa or chrysalis is a stage where the larva stops feeding and changes dramatically in form.  Pupae which are formed in the open are protected from predators by being well camouflaged or else brightly coloured as a warning.  Those protected in sheltered locations do not need such measures and are generally brown.

In the pupa the extraordinary metamorphosis takes place, and the adult form emerges gradually, often taking an hour or more to harden its wings ready for first flight.

Adults have the job of dispersing and reproducing the species.  Female butterflies can mate the same day they emerge from the pupa, while males wait for several days.
 

Eyes and colour

Hill-topping behaviour

Life spans

• at least three weeks for the Australian Admiral, Meadow Argus and Swordgrass Brown
• at least four weeks for the Cabbage White
• at least five weeks for the Orchard Butterfly
• eleven to thirteen weeks for the Common Australian Crow.

Migrations

The reasons for other migrations are harder to explain, but a number of local species are well-known for the behaviour.  These include:

• the Wood White, Meadow Argus, Australian Painted Lady, and Australian Admiral, all of which fly southwards through the ACT generally in October
• the Caper White which migrates northwards in late October-early November (it has also been seen flying in the opposite direction).

Evolution with Food plants

The earliest moth fossils are about 100 to 140 million years old, while butterflies are known from fossils dated at 40 million years.  They developed at the same time as flowering plants were beginning to proliferate and have developed in close association with them.

It appears that the egg-laying female is attracted to the plant by particular odours which we may not be able to perceive.  Before eggs are laid the essential oils of the plant will also need to provide the correct chemical stimulation to the butterfly's special sense organs on the antennae, legs and the tip of the abdomen.  Because of the role of essential oils, food plants for a particular species will often range through a plant family, such as the attraction of the Brassicaceae family for the Cabbage White.

Little is known of the reasons why many plants have developed their essential oils, but as butterflies have evolved alongside the plants they have developed immunity to the oils which may be most unpalatable or toxic to other animals.  As a result the oils designed to be a repellent have become an attractant, and in some cases a protection for the larvae or adults against predators.  However, this specialisation also limits the range of plants available for those butterflies.
 

Survival and adaptation

Butterflies need to regulate their populations so as not to threaten food plants.  While females may lay a hundred eggs, all but two need to fail to either become adults or breed, or the population will increase.

There are many animals which will feed on butterfly larvae, with vertebrate predators including birds, mammals, reptiles and amphibians, and (most importantly) invertebrate predators including spiders, praying mantis, lacewings, bugs and wasps.

Camouflage is a common adaptation in larvae and pupae, such as:

• the larvae of the Orchard Butterfly which look very much like bird droppings, and its pupae which tend to be green when on leaves or fresh stems, and grey or brown when on older stems
• the larvae of the Fringed Blue which match the pea flowers on which they feed so closely that they are hard to detect
• the pupae of the Cabbage White which can vary from green on growing plants to grey on weathered wood.

A range of birds are known to attack adult butterflies, including the Currawong (Strepera graculina), Pallid Cuckoo (Cuculus pallidus), Rufous Whistler (Pachycephala rufiventris), Black-faced Cuckoo Shrike (Coracina novaehollandiae), Fan-tailed Cuckoo (Cacomantis pyrrhophanus), and Willie Wagtail (Rhipidura leucophrys).  Some large lizards will also take adults.

All larvae also have a special organ which is used only when disturbed, flaring out to flash bright colours of red, orange or yellow, and emitting a pungent smell, while the larva rears up towards its enemy.

As protection, some species have made themselves quite unpalatable to predators.  The unpalatable species will sometimes advertise the fact with bright warning colours which will be quickly recognised by predators.  The Common Australian Crow has a strong, even repulsive scent, and like the Wanderer goes further to secrete from its food plants a range of heart poisons so strong that eating one insect can induce vomiting in a large bird.  The bird does this to avoid a heart attack, and quickly learns not to try and eat that species again!  It's a good ploy, but not all birds are sensitive to the poisons, and there are no ill effects in invertebrate predators such as spiders and dragonflies, and invertebrate parasites such as flies and wasps.

Other species which are palatable to birds have capitalised on the adaptation of their relatives by imitating unpalatable species in colour and behaviour.

Some species have developed eye-spots on their wings to resemble the vertebrate eye, sometimes set in a field of bright colour to further advertise them.  Some flash these only when disturbed to flight, while others rest with the eye-spots exposed.  The eye-spots are known to intimidate small, insect-eating birds to avoid attack, but this seems to work best at the first encounter, with birds learning quickly not to be put off.

Others have developed arrangements with ants to help protect them, presumably from parasites.  Some local examples include:

• larvae of the Common Imperial Blue, Ictinus Blue, Icilius Blue and Pseudalmenus chlorinda zephyrus which feed openly on wattles, often attended by large numbers of black Iridomyrmex ants which swarm continuously over them;
• larvae of the Fringed Blue which feed on a range of pea flowers attended by numerous small black ants
• the larvae of the Amaryllis Azure, which feed on mistletoe growing on Casuarina attended by small black Iridomyrmex ants and shelter and pupate in their galleries;
• larvae of Ogyris genoveva gela, and of the Dark Purple Azure, which feed on mistletoes attended by large yellow-brown or dark brown Camponotus sugar ants, and sheltering and pupating in their nests;
• the larvae and pupae of the Small Copper which feeds on Oxalis corniculata attended by black Iridomyrmex ants which tunnel under the plant and provide a safe harbour for the larvae and pupae in the ant galleries; and
• the larvae of both the Dull Copper and Bright Copper which feed by night on Bursaria spinosa, sheltering by day in nests at the base of the plant made by small black Notoncus and Iridomyrmex ants respectively, and usually pupating in the ants' nests.

Butterflies are also able to protect themselves against colder or less favourable weather by slowing their rate of development until conditions improve.  This ability is different for each species.  Some Canberra region examples include:

• the adult Common Brown which mates in October or November, with most males having died by early January; the females do not lay eggs until the heat of December to February has passed and lay their eggs early in March.  At this time the native grasses which serve as food for the larvae are producing fresh growth after being dry and unpalatable during the summer
• Pseudalmenus chlorinda zephyrus which remains in a pupal stage from about January to September
• larvae of the Amaryllis Azure which don't just slow down, but actually stop development altogether, going into a state of torpor along with their attendant ants.  The Common Brown seems to do likewise.

Butterflies and Moths of the Canberra district and their food plants

NOTE:   This material is incomplete research which emphasises  species and places in the Canberra region.

To obtain information, to offer suggestions or just to say hello,    please write to Healthy Cities Canberra at   mlb@rosella.apana.org.au    or   PO Box 128   JAMISON CENTRE   ACT   2614   AUSTRALIA

http://www.arandaps.act.edu.au/environment/activity/humus/buttrfly/biology.htm       Last updated 6 January 1999