Shining the spotlight on the Imperial Blue Butterfly
Posted on 6 April, 2023 by Ivan
We are constantly amazed at how talented members of our community are at nature journaling and documenting our unique biodiversity in central Victoria. We recently received a terrific article highlighting the stunning Imperial Blue Butterfly and how it interacts with other species to benefit each other. The article came from one of our members, Sandra Nowland-Foreman, who spent a decade in central Victoria, before a recent move to the coast. Sandra has taken some excellent photos and documented the symbiotic relationship between the butterfly and ants species and how to identity the species. Thanks Sandra, well done!
Imperial Blue Butterfly/Imperial Hairstreak (Jalmenus evagoras)
It is not often you encounter the entire life cycle of a creature all on one small shrub!
I was visiting the Bald Hill Reserve, a wonderful 96-hectare bushland reserve near Kyneton recently on a warm Saturday afternoon (3rd March 2023). A beautiful blue butterfly with distinct black wing edging caught my eye as I passed a young silver wattle (acacia dealbata). In the six years I had lived adjacent and regularly roamed this lovely reserve I had never encountered such a species.
Paying closer attention, I noticed the equally attractive creamy-coloured underside wings of several butterflies on its branches. The undersides were decorated with fine black spots with a pair of dainty orange dots on the lower wing ends adjacent trailing black tail filaments.
The young wattle was stripped almost bare of leaves, and I noticed clusters of pupae wedged along several upper branch intersections – some empty and others dark glossy encasements, lightly held by webbing. A closer inspection revealed an active trail of ants coming and going on the branches, attending the caterpillars, the pupae and even intermingling with mating butterflies.
My curiosity was piqued! Time for some further research…. the ants are of the genus Iridomyrmex and protect the larvae from both predators and parasites. Researchers have discovered that the Lycaenidae Butterfly species larvae and pupae use complex chemical and acoustical signals to manipulate ants (1). The larvae produce three different types of calls, and larvae and the pupae have single-celled glands over their bodies that produce attractants (2). Ants respond and attend them and are rewarded with food secretions of amino acids. In my research I also came across a video posted by entomologist Roberta Gibson from her website “Wild about Ants” related to Blue Butterflies which provides further insight into the intriguing bodily mechanisms of the larvae and pupae. This video shows the glands in its depiction of the complex ant-caterpillar interaction. Click here
The breeding season is from November to March and judging by the extent and ages of pupae encasements, range of larvae size, egg laying and active mating observed on the day, it has been a good season. I learned that adult males keep proximity to the host plant for the opportunity to mate with emerging female butterflies. Warren and Gloria Sheather observed that pupae seem to develop rapidly, within two to three weeks (Sheather, W. and G. 2020). Eggs laid late in the season do not hatch until the following spring.
The photos below show mating butterflies, larvae, pupae and eggs, with the ants which I observed during the afternoon walk on 3.3.2023.
Conservation Status:
Vic: unknown
NSW: Critically endangered
Qld: Vulnerable
Size:
Caterpillars: 2 cm
Pupa: 1.3cm
Butterfly Wingspan: 4 cm
References:
1. Pierce, N et all, The ecology and evolution of ant association in the lycaenidae (lepidoptera)
2. Gibson, R, Ants and Blue Butterfly, 10th January 2012, Wild About Ants https://wildaboutants.com/2010/01/10/ants-and-blue-butterflies/
Australian Plant Society of NSW https://resources.austplants.com.au/fauna/common-imperial-blue-butterfly-jalmenus-evagoras/ Warren and Gloria Sheather 2020
Butterfly House http://lepidoptera.butterflyhouse.com.au/lyca/evagoras.html
Naomi E. Pierce 1, Michael F. Braby, Alan Heath, David J. Lohman, John Mathew, Douglas B. Rand, Mark A. The ecology and evolution of ant association in the lycaenidae (lepidoptera) 1 January 2002
Roberta Gibson, Wild About Ants, 10th January 2012, https://wildaboutants.com/2010/01/10/ants-and-blue-butterflies/
Knox Environment Society https://www.kes.org.au/environment/fauna/imperialblue
Museum of Victoria https://collections.museumsvictoria.com.au/species/12259
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