|Weaver ants brutalizing a caterpillar|
It's a bug eat bug world, and in the insect kingdom, everything is almost certainly food for something else, as I was explicitly reminded on my way home from dinner! Pictured here are an army of red weaver ants (Oecophylla sp.) brutalizing an unidentified caterpillar. Now caterpillars are essentially the sitting ducks of the insect world. They're soft, and vulnerable, and they can't even move very quickly! Consequently, many of them have developed a variety of strategies and means through which they can defend themselves from predators (to read more about the amazing ways they do this, click here).
|Ants targeting the weak spots of a spined caterpillar|
|When attacking armored prey, like beetles, many ants have|
learnt to target the joints, the weak spots in the larger
insect's armor. Here they can inject their poison to
eventually overcome their prey.
|The brightly colored, and patterned wings of many|
butterflies are thought to function as biological
billboards that provide various signals to other butterflies
as well as animals of other species.
And so it has always been, the evolutionary arms race that began when the first invertebrate crawled out of the ocean, and so it continues to this very day. The need to feed and breed, coupled with the drive to escaped predation has resulted in the diversity and magnificence of insects we have come to know of today. Every insect's uniqueness, every part of it that stands out (aside from the basic anatomy) evolved, often for specific purposes that would aid its survival as an individual and as a species. Take the structure of insect wings for example. The wings of insects are probably one of the most diverse flight structures in the natural world as we know it and are believed to have their origin in gill-like structures possessed by some primitive invertebrates. When mosses and plants began to creep out of the ocean to colonize the shores, invertebrates were soon to follow. Not all of them, however, lost these gill like structures and many continued to retain these flap-like projections as a form of vestigial growth.
|The frontal pair of a beetle's wings have evolved into|
a virtually impenetrable,waterproof armor known as an
elytra and protects the more fragile set of flight wings
as well as the beetle's body from attack.
But as more invertebrates continued to move to land and evolved into insects, their predators were also quick to follow. It eventually became imperative once again, that insects evolved new strategies to ensure their survival and that of their species. Climbing, the unique ability of insects to scale most vertical surfaces, was believed to have evolved as such a strategy. But the most amazing of all, is perhaps the evolution of the insect wing. The flap-like projections that some insects retained as vestigial growths now developed a new purpose: it gave them the ability to glide! Gliding became an invaluable means of escape as, aside from the insects who retained this ability, there were NO flying predators at the time. This, more than anything else, led to the streamlining of the gliding process and the correspondent anatomical part to give rise to the very first insect wing making the insect quite literally, the first animal capable of sustained flight! The continued benefit of flight propelled the continued evolution of the wing resulting in the sophistication and diversity of wing design witnessed in insects today.
Some pictures of other insect wings, to give you a better idea.
|Dragonfly wings have evolved to be strong and resilient structures. They are|
waterproof and can function with great dexterity and independence of each other
allowing the dragonfly to be one of the most accomplished of aerial predators.
But of course, the evolutionary arms race in insects is not limited to its wings. In fact, every part of an insect's anatomy was originally geared towards helping the species survive each other. The barbed stings of bees for instance, was thought to have evolved as a defense mechanism against invertebrate predators. Interestingly enough, bees do not die when they sting invertebrate such as hornets and moths, which frequently invade their hives. The eventual introduction of vertebrate predators into the mix only branched this evolution out further. The following illustrated chart might give you an idea as to how this might have taken place.
This, combined with the fact that insects have been around far longer than any other living creature on the planet, and because of their fast reproduction rates, has lead insects to diversify to the point that they are quite literally one of the most successful animals on the planet! Try to remember that the next time you witness an ant carving up a caterpillar, or stop to appreciate the remarkable patterns on the wings of a butterfly. You might very well be witnessing the result and progress of the evolutionary arms race!