Each garden attracts some different insects and spiders from its neighbours because of the different food plants and micro-habitats it offers. The difference between our old garden and our new one is most apparent in the butterflies, since their caterpillars often eat only one or two species of plant.
Here we haven’t (yet) got any Plumbago, so we have no Plumbago Blue butterflies; but we do have Cycads.
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 :
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.
The short days and cool weather of our winter don’t stop our butterflies completely but do slow them down. Numbers drop off, and their hours of activity shrink. As I noted years ago, most of them find quiet spots by about 3.30 each afternoon where they can rest safely until the temperature climbs again on the following morning. The one in my photo is doing just that, but I only spotted it because I saw it land.
Do butterflies really sleep?
As this site says, it “depends on your definition of sleep. If you want to define sleep as an inactive, low metabolic state: yes. This low metabolic state is often driven by the temperature in the air.” Butterflies are ectothermic (“cold-blooded”, except that they don’t really have blood) so they need external warmth for their activity.
An extension of their overnight “sleep” is the over-winter hibernation which carries adults of some species through a long period of low temperatures and limited food supplies, even here in the tropics.
Winter may here, as I said in my last post, but the butterflies haven’t yet felt its full force. There are still plenty of flowers for the adults and greenery for the caterpillars, even on Hervey’s Range in Townsville’s cooler, drier hinterland.
These photos were taken on three successive visits between mid-April and mid-May and for this post I have simply sorted them by size: the female Varied Eggfly has a wingspan of about 85 mm, while the blues are in the 20 – 30 mm range.
Clicking on the images to see them in a lightbox will reveal extended captions including their Latin names.