Butterfly of the Month - May 2023
The Chequered Swallowtail (Papilio demoleus sthelneus) belongs to the Family of Swallowtails (Papilionidae). This attractive butterfly has a wingspan of 72mm for the male and 73mm for the female. Thanks to its wing patterns and colours it can't be mistaken for any other.
Fore and hindwings on the upper side are black with a series cream-coloured markings and a red-brownish spot with a small blue edging at the inner margins of the hindwing. At the upper margins you’ll find a slim blue edge to a black spot, unfortunately covered by the forewing in our image.
The underside of the butterfly is much lighter in appearance. The dark brown base colour is dominated by cream coloured markings. The above mentioned red-brown spots (albeit with a more orange tinge) and their blue edging repeat themselves on the hindwing of the underside. An irregular band of light yellow spots sits between them, and also forms part of the forewing. Male and female are very similar.
While there are several subspecies of Papilio demoleus, only one (Papilio demoleus sthelneus) can be found on the Australian mainland.
The life cycle starts off with a pale yellow globular egg of a little over 1mm. Our example is slightly further advanced and shown in magnification. Eggs are laid singly, usually on the upper side of the larval host plant’s leaves.
While the different instar stages may vary in colour patterns, the emerging larva starts black-brown, but tends to show white and orange coloured flecks through the subsequent instar stages. However, the 5th instar stage just before pupation is green with fine black lines between each segment and small orange or white spots.
The pupa is attached to a silk pad on the host plant stem by tiny hooks at the abdominal end of the cremaster (a small ‘stem’ like structure). Silk threads are woven around those hooks and hold the pupa firmly in place. Additionally, the pupa is secured by a girdle. The green colour shown here blends beautifully with the vegetation they are attached to. Pupae may also appear in brown colouration.
Adults are known for their rapid flight behaviour, up to 3m above ground, and for their ‘mud puddling’. During the latter they drink from moist soil areas and thereby obtain nutrients they would otherwise not find.
Papilio demoleus has been recorded across mainland Australia. Adults are migratory in search of favourable conditions, although generally in smaller numbers than known from other butterflies.
In Brisbane the butterfly uses Emu Foot (Cullen tenax) as its preferred native larval host plant, but may also use Round Lime (Citrus australis) and Finger Lime (Citrus australasicus).
MV – Museum Victoria (Ross Field and Simon Hinkley); SA – Sylvia Alexander; WJ – Wesley Jenkinson