Fascinating Invertebrates

By Sean Fagan

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Creepy Crawlies

 Getting to Know the Small Inhabitants of Nature 

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I urge you to walk into any area where there is woodland, ditch, grass, rock-pool or pond. Now, lie down on your belly. Get really close and watch - without judgement or expectation.

After a while, when you become more relaxed and your mind becomes attuned - a world of incredible diversity and activity will slowly reveal itself.

To my mind, there is nothing quite as magical as the reality of nature.

Modern day living has done its part in removing us from the visceral, majestic and fascinating world of nature but there is very little that surpasses observing nature and infusing oneself with its minutiae and peaceful pace. And nature is wonderfully spontaneous.

Within this microcosmic world of invertebrates live a myriad of characters that sometimes cheat, kill, protect, cower and cavort to name but a few general characteristics.

Contrary to popular belief that only the strong will survive in nature there are many animal and plants that regularly break this rule. It all depends on your definition of strong. I would modify that saying by stating that only the strong survive but also the crafty and adaptable will thrive too.

But I digress. I want you to join me on a journey that I sincerely hope you will participate in, sometime in the very near future for there are creatures under our feet that are tremendously fascinating. Some are long, some short, some with many legs, and some with none at all. Some have shells, some are jelly-soft. Some are ferocious and some - docile. And where do these creatures exist?

Pretty much everywhere!

Lift any stone in any woodland or garden, and you will probably recoil at the creepy crawlies scuttling around for cover. But take a closer look and you will discover a miniature ecosystem as fascinating and ruthless as the Serengeti plains of Africa, as intensely competitive as a verdant rainforest and finally, as old as the earth itself.

It’s all a matter of perspective.

Let me introduce you a creature you all know. There is an animal commonly found under stones that evolved from marine dwelling crustaceans 160 million years ago?

Crustaceans are typically creatures of the sea, such as crabs, lobsters and shrimps. So, some 160 million years ago this once marine creature made very short, furtive forays into the terrestrial world, away from the familiar refuge of the sea. Eventually they evolved the ability to live on land.

However, they retained some of their marine ancestry for they do not have lungs like most terrestrial animals but gills, modified gills. Such gills restrict the habitat preferences of these creatures to the dark and dank cryptozoic refuges that are typically found under stones and decaying wood. Because they possess gills this creature cannot tolerate prolonged exposure to the outside world and would quickly shrivel up and die from desiccation, (otherwise known as dehydration).

In addition, its thin, shell-like skin is not waterproof and they lose moisture relatively easily through there skin. They also have a brood-pouch, a modified, bag-like appendage that hangs tightly from its underside and within this brood pouch, which is moist and partially fluid filled, the young are hatched inside and allowed to grow to some extent before being released into the wild. This brood pouch is not unlike the marsupial pouch of a kangaroo and has a similar function: it protects the young and allows them time to develop until they are able to look after themselves.

This creature has fourteen sturdy legs and can, because of its flat, wide body exert great vertical pressure relative to its body size so that it can squeeze itself into the smallest of cracks and openings that are typically found under rocks and dead wood.

You know this creature; you probably held them in the palm of your hand when you were child, uninhibited with wild curiosity for everything that moved. It is a creature that is incredibly prevalent; some studies have shown they can reach a maximum density of approximately 1000 individuals per square metre in mature, deciduous forests. They are sometimes technically categorised as primary decomposers as they are able to devour the course organic waste of woodlands, thus ensuring the essential, cyclic return of nutrients to trees and other plants of woodlands.

They are the humble woodlouse.

There are other wonders: there is animal that silently dwells at the bottoms of ponds. It waits with a chilly stillness, camouflaging its long, dark body in the weedy morass of ponds, and then finally, with lightening speed, strikes. It is a ravenous predator on unsuspecting animals in ponds. It is sometimes colloquially called the water-tiger and for good reason - for in the murky world of the pond the water-tiger is a fearsome creature. And yet the water tiger is only about an inch long.

One of the distinguishing characteristics of water tigers is that they are very slow moving. Water-tigers are what is termed ambush predators and are able, just like the jaguar of the Amazonian rainforest, move short distances very quickly in order to capture prey. The water-tiger has another, almost overpowering, physical feature, which ensures their success as ambush predators, their jaws. Water tigers have proportionally huge, pincer-like jaws. The jaws are needle sharp and once an unsuspecting prey is impaled within their deadly grasp, it is doomed to die from a combination of puncture wounds and the undignified sucking of its life-fluids as the water tiger is also equipped with an additional mouth part between its jaws, which resemble a minute hypothermic-needle.

When a prey item is securely seized the water tiger proceeds to pump digestive enzymes into the prey with the aid of this needle-like mouthpart, which rapidly digest the organs and the tissues of the prey into a mushy, liquid-like consistency which is rapidly sucked up by the water-tiger.

Interestingly, the water tiger has evolved from a land dweller, a beetle in fact, for the water-tiger is the aquatic larvae of a beetle that also lives in ponds for the duration of its life. However the adult beetle has one advantage over its larvae, it can fly. Ponds are transient habitats, prone to drying up during the summer. The adult beetle can therefore fly to other ponds where fresh food resources and the possibility of finding a mate are possible, thus ensuring the species survival.

The name of the adult beetle phase of the water tiger is called, aptly, the great diving beetle, and can grow to a prodigious 2 inches long and is an equally fearsome predator as the larvae. Incidentally, the beetle body plan of a hardened outer shell, which gives them the appearance of a small armoured tank, has proven, over many millions of years to be an unusually simple and successful design in the insect world. The hardened outer case of beetles is termed elytra and was evolved, quite ingeniously, from a pair of wings that hardened over time to provide a hardened case that protects beetles from a myriad of predators and adverse environmental conditions. Under the elytra there is usually a single pair of wings that just about, keep beetles aerodynamically competent and aerially mobile, thus increasing their ability to colonise just about any land on the planet.

Beetles, in fact, are so prolific, so successful, that there are more species of beetle than any other category of insects, or any other category of living organisms, on the planet. The famous zoologist, John Haldane, was once asked in an interview did he believe in God, and did his extensive scientific work reveal anything about the mind of God? Haldane sat back, taking a leisurely drag from his pipe, while savouring the question. At last he replied, with a singularly original answer “The Creator, if he exists, has an inordinate fondness for beetles". And it would seem that Haldane’s pertinent assumption is probably not far off the truth for beetles seem to populate every nook and cranny of this wonderful earth with wondrous and industrious ingenuity and outright gusto, for beetles account for 25% of all known animal species so far recorded, on planet earth. That’s a huge proportion of life as know it. Maybe it’s a wild assumption to make but maybe it can be assumed that if the human race should become extinct in the future then beetles will be one of the first life forms, through evolution, to crawl life back into its former sophisticated glory : )

Insects are a phenomenal success story of evolution, partly because they possess water proof skin, composed of chitin, which enabled them to virtually explode into every available terrestrial niche without drying up.

The evolutionary success of insects was also made possible with the parallel advent of the angiosperms, the flowering plants, which also ravenously occupied most terrestrial niches available some 250 million years ago. Many insects and flowering plants depended on each other for there survival. Many plants evolved insect pollinated flowers in order to disperse there kind while insects in turn were provided with a rich source of nutrients from the plant: nectar. Plants also provided a source of leafy food matter and a physical shelter for many evolving insects. And so a silent, mutual partnership developed between insect and flower for many millions of years. Together, they survived the mass extinction of the dinosaurs 65 million years ago and the subsequent drying and freezing climate episodes that caused many other creatures to perish.

And here they are today, alive and well and thriving with an intensity that is a little unsettling. For even though humans have exterminated many species of birds and mammals into extinction they have not managed to exterminate a single species of insect. Why has this occurred? It’s simple; insects are generally small, adaptable and are able to play a very clever game involving numbers. In short, they breed like crazy.

Insects multiply in there hundreds, thousands, millions even. They are almost unrivaled in their prodigious output of offspring.

So next time you are wandering through a wood, a meadow, your garden or any other wild area take a closer look at the ground and wait. You need to get your face right in there. Within minutes the ground will begin to crawl, sprint, hop and clamber as its minute denizens go about their daily business. Some will shine iridescent, some will be intricately patterned, some will be dull, some aggressive and some plain old predictable. It’s the variety that enthralls, that makes you aware of a delicate ecosystem so very, very fascinating. Enjoy, for you are also part of this natural plan.