Papagaios, Life & Times on a Speculative Archipelago - Giant Insects of Papagaios

Script* from show ‘Minibeasts of your Backyard’ performed at the Papagaios Zoo. Show has been performed since 2010 and the script is a guide for presenters who often put their own spin on it and respond to the demands of the audience.

(*Translation from Portuguese)

When we talk about the animals found in a place we normally focus on the big, impressive ones. Lions, elephants and rhino on the Serengeti; polar bears and walruses in the Arctic; and even here on Papagaios we favour the lizards and birds over our smaller neighbours. Yet, the world of invertebrates is fascinating, and often more complex than the realm of megafauna.

So let’s meet some of the smaller residents of the islands, and if you’re brave, you might get to touch them yourself!

Insects were among the first living things on the islands, once enough plants had grown for them to eat. Being so small, it would be easy for them to get blown away from the mainland in a storm and some lucky few found dry land. Once they dried off, they would find a feast of plant life spread out before them and no larger animals, either to eat it – or them.

Endless food and no predators is a recipe to get big, we see that in Galapagos tortoises, in dodos, and in the insects of Papagaios. Take ladybirds. If you were to find a ladybird in Europe, or North America, it would be, at most, one centimetre long. Papagaian ladybirds are somewhat larger. We have smaller species sure, but the Megacoccinella genus, that are found only here, average four centimetres long. An extinct species, Megacoccinella goliathus measured nearly ten centimetres, if you can believe that. Today, though, they don’t get much bigger than this one here, the Two-Spotted Cranberry Ladybird, five and a half centimetres long. If you give me a second, I’ll get it out of the tank…

[…]

…Ladybirds are adaptable and can eat a range of food, usually smaller insects, but some are herbivores or omnivores. Grasshoppers on the other hand are always herbivores… except here. Being naturally larger, faster and with strong jaws adapted to cut through the toughest vegetation, they were well-placed to become apex predators of the pre-vertebrate islands.

Carnivorous grasshoppers, like this 10cm long Red-Armed Saddleback [gesture to insect in tank], have several specialisations to carnivory. In addition to one of the strongest bites in the insect world, they possess spines along their front legs which aid in grappling wriggling prey.

We’re not sure when they first became carnivores, or how. Fossils show they were definitely hunting prey by 30 million years ago, but it may be as far back as 33 million. I suspect that the first grasshoppers were so greedy in devouring the infinite banquet they found that they didn’t notice if they occasionally took a bite of another insect while eating the leaf it was on. Eventually, some grasshoppers began deliberately targeting insects in addition to plants, moving to omnivory, and eventually gave up on plants entirely.

Now we’ll have to be careful, and only I’ll be able to handle him, but let’s see if this fella wants to come out and play…

[…]

…Caterpillars are another success story on the islands. It was a lucky butterfly that made it out of a hurricane in one piece, but enough of them made it that our islands now have an abundance of species found only here. This one [get out of tank] is one of my favourite species. If it took you a second to realise it was a caterpillar, you’re not alone, this critter is a mimic. That means it has evolved to look like an entirely different animal as a way of scaring off predators. In this case, it looks like a tree lizard. Now if I was a predator and saw this [point at part mimicking lizard’s head] peeping out from under a leaf, I’d think there was a pretty big lizard attached and might reconsider trying to eat it.

A few native caterpillars are mimics, but there are other quirks they share. An unusual feature in many Papagaian caterpillars is neoteny – the ability to retain juvenile features or to stay in a juvenile form throughout life. Think of axolotls which spend their whole lives in a tadpole-like state.

Neoteny exists in most Papagaian caterpillar species to varying degrees. For the majority, the caterpillars form a chrysalis, but only the males emerge as butterflies. The females, in contrast, look more or less as they always did, the main difference being they are now able to reproduce. Males, retaining flight, can still travel to find a mate, maintaining genetic diversity across areas.

Caterpillars were among the first arrivals in the archipelago, around 40 million years ago. They had no predators at this time, and so a fast-moving but energy intensive adult form would have been a waste of resources. This is likely why neoteny first developed, to save energy and allow the individual to reproduce more and thereby have more offspring, propagating the trait.

Females retaining their larval form also allows them to continue eating vegetation, keeping them alive far longer than the males which die in a few weeks having only consumed sugar-rich nectar during their search for mates. In many species of caterpillar, the neotenous females survive for a second breeding season. In a select few species, they live for five years or more. The arrival of lizards and birds in the years to follow no doubt greatly curbed their success, but enough species survived to allow the Papagaios Islands to be a unique ecosystem with caterpillars living in ways that are rare elsewhere.