Insects are a class of invertebrate animals, that include more than a million described species and they represent more than half of all known living organisms. The most numerous order is the Beetles (Coleoptera), with over 400,000 named species. All insects can be recognised by having three body segments, six legs, and two antennae. Many species have evolved wings and can be seen flying. Below are a few interesting facts about the extraordinary behaviour, that some of these small creatures have evolved.
The Feather-Legged Bug
The Feather-Legged Bug (Ptilocnemus lemur from Australia pictured), which is an Assassin Bug (Reduviidae), has evolved a unique hunting technique: it places itself on Ant trails, waving its feathery legs to attract attention, and once an ant approaches, the bug will raise itself on its long hind legs, exposing a gland on its underside. The Ant will eagerly lick this gland, and that will be the last thing it ever does, because this gland secretes a poisonous fluid which immobilises and kills the ant. Now the bug only has to pierce the Ant’s shell (usually the soft part between head and thorax) with its rostrum and suck up the dissolved internal tissues, which are broken down by the Bug’s saliva. This hunting technique prevents the Bug from having to engage Ants in a fight, allowing it to feed even on fierce australian Bulldog Ants, that posses themselves a powerful poisonous sting. The Ants don’t seem to recognise the Bug as an enemy; perhaps it is able to make itself “invisible” by producing an ant pheromone.
Some peculiar Ant species
Some Ants have evolved very unusual feeding habits and ways to obtain food. For example the Leafcutter Ants (Atta sp from Ecuador pictured) from South America, as the name suggests, cut leaves and bring them back to their nest, all day, every day. Nothing too unusual so far, but the reason these ants cut and store leaves, is a bit more peculiar. They do not eat these leaves themselves, but rather use them to cultivate their gardens and grow their own food crop: and their crop is an edible fungus. This fungus only grows in these ant-nests, under these very specific conditions. There is a downside to this fungus though – it releases carbon dioxide. But the Ants have overcome this inconvenience with mastery: their underground nests are fitted with vents on thesurface, that are precisely engineered to take an inflow of fresh air, and suck out the stale air and carbon dioxide, providing the best living conditions for the Ants and their food crop. These small animals have perfected techniques that are usually thought of being exclusively human.
Other Ant species, like the Common Red Ant (Myrmica rubra from Germany pictured) are more into animal-farming. They have established “farming” relationships with Bugs. These Bugs feed on the sap of plants and, as a by-product of this feeding, they excrete honeydew, a sugary fluid that the Ants are very keen on. In order to get as much honeydew as possible, the Ants make sure that the Bugs are always brought to the best feeding grounds (actually carrying them!), providing protection and shelter for their “dairy cows”. Ants are known to carry their “bug herds” into shelter during rain and storms, or even into their own nest over night. This relationship is beneficial for the Bugs too, since the only thing they have to do is feed and excrete honeydew, while the Ants do the hard work.
Considering this behaviour, one could almost think that these Ants have taken the step from hunter-gatherers to subsistence farmers, which somehow sounds quite familiar, doesn’t it?
The 17-year Cicada
The 17-year Cicada from the east of the USA, only surfaces for a few weeks in their (for Insects) long lives. These periodical cicadas spend 13 or 17 years underground, until they are ready to emerge. Thousands of nymphs come out of the ground at about the same time, where they moult for the last time and become winged adults. The purpose is to mate and their courtship calls make it the loudest insect in the world. After two months, the adults will have died, but their eggs will hatch becoming the new generation that will again emerge in 13 or 17 years.
These remarkable creatures have developed an astonishing way of providing for their offspring! As the name suggests, many of these solitary Spider Wasps in the Pompilidae family, hunt spiders. Now, these are not food for the wasp, but will feed the wasp’s larvae (the adults feed on nectar). Once the wasp has located a victim, it will attack it and paralyse it with a venomous sting. The paralysed victim will then be carried to the wasp’s burrow, where the wasp deposits one egg on the spider’s abdomen, and then proceeds to seal off the burrow. When the egg hatches, the larva will have a good supply of fresh food, as the immobilised spider continues alive. To ensure that, the larva will leave the vital organs for last.
These Wasps are very aggressive and determined hunters: I was able observe one species in east Ecuador, that put in a great deal of effort to catch a Sac Spider (see thumbnails). The spider had woven two leaves together on their flat sides, forming a seam around the edges, with a “pouch” in between. The wasp, knowing the spider was in there, started to chew at the rim of the stuck together leaves, creating an opening through which to enter and extract the spider. Leaves are made of pretty tough cellulose, and it took the wasp a few minutes to chew through them, but eventually it did and pulled the unfortunate spider out. Before carrying it away, it started to dismember it.
I’d seen this behaviour before from other species in Australia, and I assume this will further ensure that the spider doesn’t move, while the larva feasts on it.