|
|
 |
Home
 Creature Features |
 
|
|
| Orchard Swallowtail (Papilio aegeus aegeus) |
| Article by Bob Miller, December 2002 | |
Are you one of the many people who have seen caterpillars on the citrus trees and wondered what they were? If so, this article should prove to be interesting for you.
There are actually three butterflies in south-east Queensland whose larvae use citrus trees as their foodplants, the Dainty Swallowtail (formerly Dingy Swallowtail), the Fuscous Swallowtail (formerly Capaneus Butterfly) and the Orchard Swallowtail.
The latter is the one we are concerned with in this article and most will recognize its larvae as the ones that look like bird droppings. The young larvae are brown with white markings and as they grow older, can be a variety of different colours, varying from yellowish-green with white markings, to very dark green with white and brown markings.
All swallowtail butterfly larvae have a built-in chemical defence mechanism, called an osmeterium. This is the name given to a pair of fleshy tubes that extend from behind the head of the larvae when they are being attacked. In the case of the Orchard Swallowtail, the tubes are red and emit a fairly strong citrus-like odour. If you find any of these larvae, tap them on their backs, they will think they are being attacked and instinctively raise the osmeterium. Run your finger along the red projections and then smell your finger. If you were a bird, would you keep attacking?
When fully grown, about 60mm long, they will search for a suitable place to pupate. This is usually on the underside of a leaf of the foodplant, or on one of the branches or branchlets. Once there, the larva spins a silken pad, on to which it attaches itself by the tip of its abdomen and a central silken girdle. It will then shed its skin for one final time, to become a pupa.
The pupae vary in colour, usually depending on where they pupate. Camouflage is their best defence once they are attached to the plant. The pupae found on the underside of the leaves are generally lime-green in colour, whilst those found attached to the brown stems, take on that same brown colour.
The adult butterfly is one of the largest found in south-east Queensland, with the male having a wingspan of about 11 cm and the female slightly larger at 13cm. The male is primarily black on both upper and undersides. The upperside has a series of white or cream markings near the tip of the forewings and a cream patch with one red anal spot on the hindwings. The underside of the male forewing is similar but the hindwings have a narrow marginal band of cream with crescentic lines of red and blue semi-lunate spots on the black background.
The female butterfly looks greyish-white overall and is very similar on the upper and undersides. The forewings have a large brown-black patch near the body and a series of narrow brown lines running horizontally to the wing margin. The hindwings have the same dark patch near the body, then a white patch, followed by a broad, dark band along the outer edge of the wings. Inside this dark band are crescentic lines of red and blue semi-lunate spots (generally with more blue on the underside) and red anal spot as for the male.
Apart from the common citrus trees, there are also a wide range of native plants, including Micromelum minutum, Clausena brevistyla, Geijera parviflora and Flindersia australis, on which the larvae feed.
Further information can be obtained by reading Butterflies of Australia , by Common and Waterhouse, 1981, or Butterflies of Australia their identification, biology and distribution by Michael F. Braby, 2000 CSIRO Melbourne.
This article by Bob Miller, appeared in Newsletter Issue Number 27, December 2002.
|
| | |
|
|
|
|
