Macro Monday Blues

This little beauty is a silver-studded blue, Plebejus acmon, photographed somewhere along the Southern Californian coast between San Diego and Los Angeles. To be honest, it is more commonly known as an acmon blue, but I thought the alternative name was much nicer.

I love these little blue butterflies. They are so delicate and yet so hardy, able to survive in the harsh windy and arid environment of the Californian coastline. Their markings are exquisite and who wouldn’t want such a gorgeous pair of stripy antennae? They do have a few survival tactics up their scaly wings. The most interesting one is an association that they have with ants. You see, ants are a very sociable bunch and though they are small, there is strength and safety in numbers. One ant is not a problem, but who wants to take on a whole army of them, what with their bitey jaws and stinging backsides? So, what the defenceless little blue caterpillars do (the caterpillars are actually brownish yellow, if we are going to be accurate here) is to pay the ants for some protection. Each caterpillar is equipped with a honey gland which emits a sugary solution which is to the ants' liking. The ants will protect the caterpillars from predation and then go to the ant for the payoff – a nice large droplet of sugar solution. The caterpillars can go one step further and even call for help if required. They have a pair of tubercles on their abdomens that can emit a chemical that mimics an ant alarm pheromone. This makes the ants think that they are under attack and so they all rush to the aid of the caterpillar, resulting in a frenzied and aggressive defence. Everyone is happy, everyone is a winner (well, except for the would-be predator of the caterpillar, who loses out on lunch and gets terrorised by ants). Nature, all cosy and cooperative.

I could leave it there, letting you all swan off believing in the benevolence of Nature, but let’s keep things in perspective. Where Nature is concerned, it is every species for itself and each species will do what benefits it the most. For the silver-studded blue and the ants, the alliance is holding strong. But, as in all alliances, it relies on both partners cooperating fully and equally. And, as in all alliances, there is always the chance that one side might betray the other - come on, you all must have seen this happen time and time again on Survivor. In the ant / blue butterfly alliance, there are some very good examples of where the flirty, flighty, innocent-looking butterfly has become the ant’s worst nightmare. One example is the large blue butterfly, Maculinea arion, of England. This gorgeous creature was declared extinct in England in 1979, but has since been reintroduced to several sites in Southern England. The caterpillars begin life feeding on the flowers of wild thyme, but after several moults, they fall to the ground where they pretend to be ant grubs. If they are lucky, some unsuspecting ant will come along and, after much scrutinising, will decide that some poor baby ant has lost its way, pick it up and take it back to its nest. The caterpillar deceives the ant both visually, by rearing up on its legs to look like an ant grub and chemically, by emitting a chemical soup that makes it smells just like an ant. Once the caterpillar makes it back to the ant’s nest, life is good. It spends its time pretending to be an ant, being looked after and protected by the ants while dining away on the ant’s real offspring. This is one of the few examples of a carnivorous caterpillar. The chemical deception continues as the caterpillar pupates and transforms into the lovely adult, which, once it emerges from the pupa, hightails it out of the nest before it expands its wings and flutters away.

Of course, the butterfly does not have it all its own way. One of the reasons for all this trickery is to get below ground into the safety of the ants’ nest, out of sight of potential predators. However, some predators are so good they can still sniff them out no matter where they are. In this case, there is a parasitoid wasp that is able to find the blue caterpillars. It is able to track them down into the ant’s nest. Once it reaches the nest, it too douses itself with ant pheromones so that it does not get attacked by the ants. It then enters the nest and is able to pick out the caterpillars from the ant grubs. No-one knows quite how it achieves this amazing olfactory feat, but it does. Once a target has been identified, it injects an egg into the caterpillar. This egg will then hatch and the wasp grub will grow inside the caterpillar, slowly eating it from the inside out, leaving the most vital organs until last to ensure the meal stays aliveand fresh for as long as possible. The wasp grub then pupates inside the caterpillar, nice and safe from the ants, to later emerge as a shiny new adult, which also hightails it out of the nest as quick as it can.

Nature - beautiful, magnificent, glorious and delightful.

Nature - sinister, deadly, macabre, and unforgiving. Survival of the fittest indeed.

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