A tiger in the bushes

Why are some butterflies called by common names such as ‘tigers’ and ‘crows’? If anyone can enlighten me, I’d appreciate it.

I saw this blue tiger (Tirumala hamata) in Ballina last week.

Blue tiger butterfly, Tirumala hamata

Near Kempsey; photo by Christa Schwoebel

These butterflies live all year round in north Queensland and migrate in spring and summer generally down to just south of the Queensland border, meaning we are pretty much at the southern-most end of their range (see the distribution map in Michael Braby’s book). But they occasionally venture further south when conditions are good for their main larvae host plants, one of which is corky milk vine (Secamone elliptica).

According to Land for Wildlife (South-East Queensland):

Corky milk vine contains several chemicals that are poisonous to many animals, but not to the blue tiger larvae. When the larvae eat corky milk vine, the poisonous chemicals get passed on to the pupae and adult butterflies. These toxins then work to protect adult blue tigers from being eaten by birds, as birds have learnt that they get sick from ingesting blue tigers.

The butterflies migrate back to the north in April and May (our autumn) and are known to over-winter in large clusters. Individuals may live up to six months.

According to Kath Vail:

The adult male butterflies are strongly attracted to the pyrrolizidine alkaloids that are also found in the Parsonsia vine, known as common silkpod or monkey rope. The male will scratch the leaves to release the sap which they imbibe, and then they convert this complex organic compound into sex pheromones.

Courtship for the blue tiger butterflies includes extensive use of hair pencils that are located at the tip of the male’s abdomen. It is quite rare in nature to see the hair pencil display; however, it involves the hair pencils being charged with perfume from scent pouches on the upside of the wing. The male then erects these hair pencils and dusts the female with the pheromones.

It is important to plant both the corky milk vine and the Parsonsia vine together if you want to provide the most benefit to the blue tiger butterfly.

Obviously the butterflies do not feed exclusively on these vines – the Ballina example shows that. Even though these butterflies are quite common, it’s still uplifting to see them.

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2 Responses to A tiger in the bushes

  1. Christa Schwoebel says:

    Hello Joy, Oh, the wonders of nature! Fascinating background. I always enjoy how you bring out information and connections. Sort of, take me behind the scenes, show the invisible. Cheers Christa

    I took this photo just over a year ago on one of my favourite walks near Hat Head. Of course until today I didn’t know anything about this butterfly.

    >

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