Walking back down the hill for Tegoora Rock lookout (previous post) I spotted a green-ant nest with – surprisingly – a butterfly perched on it. Living dangerously, surely? Perhaps not.
I had vague memories vague of mutually beneficial partnerships between butterflies and ants so I looked them up when I got home. The butterfly guide books (and sites) generally just note the “attendant ant” species and the food plants, e.g.
The caterpillar is aways attended by the green ants :
It usually hides by day under a leaf, and feeds by night on the leaves, young shoots, buds, and flowers of a wide variety of plants, including :
- Pudding Pie Tree ( Cassia fistula, CAESALPINIACEAE ),
- Sandy Mangrove ( Lumnitzera racemosa, COMBRETACEAE ),
- Black Bean ( Castanospermum australe, FABACEAE ),
- Supplejack ( Flagellaria indica, COMMELINACEAE ),
- Glory Bower ( Clerodendrum inerme, LAMIACEAE ),
- Billy Goat Plum ( Planchonia careya, LECYTHIDACEAE ),
- Long Flowered Mistletoe ( Dendrophthoe vitellina, LORANTHACEAE ),
- River Mangrove ( Aegiceras corniculatum, PRIMULACEAE),
- Powder Puff Lillipilly ( Syzygium wilsonii, MYRTACEAE ),
- Yellow Mangrove ( Ceriops tagal, RHIZOPHORACEAE ),
- Carrotwood ( Cupaniopsis anacardioides, SAPINDACEAE ), and
- Barbed Wire Bush ( Smilax australis , SMILACACEAE ).
The Caterpillars pupate on the stems of the food plant, often in groups, head down.
That’s from the Herbison-Evans and Crossley site’s page about the Black-spotted Flash, which they call the Common Tit. (Perhaps it is “common” because it has so many host plants?)
The best short explanation of the relationship’s benefits I found was this:
The butterfly family Lycaenidae (including the Riodinidae) contains an estimated 30% of all butterfly species and exhibits a diverse array of life history strategies. The early stages [i.e. caterpillars] of most lycaenids associate with ants to varying degrees, ranging from casual facultative coexistence [i.e. they help each other but don’t need each other] through to obligate association where the long-term survival of the butterfly is dependent on the presence of its attendant ants. Attendant ants guard the butterflies against predators and parasites during their vulnerable period of larval growth and pupation. The caterpillars, in return, reward the ants by providing attractive secretions from specialized glands in their cuticle.
That’s the introduction to a thesis, Ant Association and Speciation in Lycaenidae (Lepidoptera): Consequences of Novel Adaptations and Pleistocene Climate Changes, by Rodney Eastwood (pdf here). The thesis itself is concerned with tracing associations between ant species, the butterflies they care for, and the butterflies’ host plants; I know a couple of people who would enjoy it but the general idea is enough for most of us.
An article by Eastwood (again) and Ann Fraser in Austral Ecology, “Associations between lycaenid butterflies and ants in Australia,” gives us some statistics:
Nearly 80% of the lycaenid species in Australia, for which the early stages are known, are recorded associating with ants and half of these are obligately ant-associated. … Lycaenids are recorded with five ant subfamilies … All ant species that tend lycaenids spend at least some portion of their time foraging on vegetation to collect plant and insect nectar.
As I said in an earlier post, male butterflies often hang around their caterpillars’ food plants waiting for females to come and lay eggs, and it is quite likely that the one I photographed is doing just that. And if the ants recognise the caterpillars through chemical cues, the adult probably produces the same cues and will be safe on their nest.
Finally, here is the female of the species, which I photographed at the other end of the Common a few years ago.