“What makes things baffling is their degree of complexity, not their sheer size…. A star is simpler than an insect”.
Martin Rees. “Exploring Our Universe and Others”.
I come from a family that loves insects. As biologists, we have learned to unravel the fascinating world of these little creatures. Normally, most people don’t “love” insects, but normally people don’t get to explore them and their world as close as we have. Or even worst, normally, people’s daily encounters with insects have been reduced to the unwanted visits of cockroaches, mosquitoes, ants and spiders, which they want out of their house or dead, as soon as possible. Getting to see these creatures in their natural habitats, learning how valuable they are in our ecosystems and understanding the traits that make them the most biologically successful group makes it easier to be amazed and even care for these wonderful organisms.
The small creatures we are admiring here, were portrayed in a very special place in Costa Rica; Sirena Biological Station, located in the heart of the Corcovado National Park, one of the most biodiverse places on earth. This remarkable patch of wild land, (fortunately my work place and second home), is known by scientists and students from all over the world, and is perfectly defined as a dream spot for those who are adventuring to study tropical ecosystems. It has a network of trails that move along two main rivers: the Claro River and the Sirena River, allowing wildlife around the station to be extraordinarily abundant, especially insects, or more generally, arthropods (invertebrate animals).
Arthropods are the most biologically successful group of animals on the planet; they are more diverse and live in a greater range of habitats than any other phylum of animals. Approximately 1.9 million species of animals have been described so far; 900,000 are insects, compared to about 50,000 vertebrate species found all over the globe.
Looking back, the history of humans and insects share a common milestone. The evolution of extreme insect superorganisms, much as human civilizations, was attained by agriculture: a form of mutualistic symbiosis of animals with plants or fungi. Human agriculture, which originated about 10,000 years ago, was a major cultural transition that catapulted our species from a hunter-gatherer lifestyle to a technological and increasingly urban existence, accompanied by an enormous expansion of population. The most advanced agricultural insect societies, like their human counterparts, rose to ecological dominance. The trend is especially marked in the example of the leafcutter ants. The evolutionary invention of cutting and harvesting live plant material opened up a huge new nutritional niche for the Atta species. Nowadays there are five distinct agricultural systems in attine ants (fungus grower ants). Biologists estimate that leaf-cutter ants carry off 15 percent of the leaves in Neotropical forests to feed to their fungal gardens.
Their organizational structure is no less impressive than their feeding techniques. Leafcutters life cycle consists of only one queen, an exclusive reproductive individual, and millions of sterile workers of different size. Each year, mature colonies produce young reproductive females and males, called the alates, who depart from their mother colonies on mating flights. The flights of all Atta colonies belonging to the same species and living in the same habitat appear to be synchronized. Around the Sirena Biological Station, guides and naturalists have observed thousands of dead alates on the forest or beach ground, after they have enjoyed a flying orgy and multiple mating was achieved on the air; scientists believe these actions also reinforce the colony’s vitality and resistance to disease in insects’ societies.
Furthermore, taken as a group, and viewed on a grand scale, arthropods have achieved a series of traits that make them fit survivors. They metamorphose –or at least most of them do– growing up as larvae and later taking off freely in the sky.
They have opted for direct sperm transmittal through insemination, thereby relinquishing forever dependence on water for spawning. And as a consequence of acquisition of an exoskeleton –an external skeleton consisting of a hard cuticle– they have attained quickness of motion, resistance to desiccation, and the capacity to achieve dominance on land. Another interesting fact is that all arthropods have to undergo "ecdysis," the moulting of their shells to allow them to grow or transform (a nice metaphor on letting go of what constraints the ability to expand). Finally, nothing more extravagant and surprising than their compound eyes and their antennae; this alien looking eyes made up of repeating photoreceptors, the ommatidia, each of which functions as a separate visual receptor, are made to detect light, UV and color; while the antennae are perceptive to signals such as pheromones for mating and communication. While humans could get lost even with a compass, insects will always find their way in the vast forests where they live.
All these characteristics make arthropods impressive on their own stand; yet, when we learn about their role in the larger ecosystem, they become even more amazing and what’s more: absolutely necessary. Given their sheer numbers, it's no surprise that arthropods lay at the base of the food chain in most ecological systems. Without the pollination of plants and crops provided by insects, our agricultural economy would collapse. Bees, wasps, ants, butterflies, moths, flies and beetles are invaluable agents of pollination. Pollens and grains become accidentally attached to their chests and legs and are transferred to other agricultural crops, either walking or flying. Most plants actually produce scents to send signals to insects indicating that food in the form of nectar is available.
On the other hand, mites, ticks, centipedes, and millipedes are decomposers, meaning they break down dead plants and animals and turn them into soil nutrients. This is an important role not just because it keeps dead material from accumulating in the environment, but also because it supplies the plants with the minerals and nutrients necessary for life, which also are passed to the animals that eat the plants. Even the world's greatest predators and humans rely on this role to survive.
Even cockroaches, vilified by humans as one of the most despicable creatures, have a crucial place in the ecosystem design. Cockroaches have the effect of releasing nitrogen in their feces, which then gets into the soil and is used by plants. In the tropics, cockroaches feed on decaying wood and leaves. They help break down this organic debris and in the process they add nutrients to the soil through their waste. Plus, they're of course a food source for small reptiles and mammals.
In sum, insects are the most versatile of evolutionary innovators. Pick an insect at random, and chances are there is something about the way it feeds, defends, or reproduces, that is unique and remarkable. When looked closer (both literally and conceptually) insects can surprise us with some of nature’s most amazing works of art and wisdom; and thus, they can become a source for admiration rather than despise. In fact, two of the main traits that make insects so successful are things humans could really take note on: their cooperation and their true sustainability. The ways some of the insect species care for each other within their ‘eusocial’ organizations, and the myriad ways in which they seize and give back natural resources in their ecosystem, are clear evidence that criteria like cooperative care, and taking only what you need are key aspects for ultimate success. Insects do all of this and more, providing a secure future both to themselves and for their plant partners and their larger ecosystems. Literally, succeeding at life.
No reason then to misprize an insect of any kind, taking the time to learn from it will always show us something that will undoubtedly amaze us. Coming closer to their sometimes invisible worlds can once more remind us of how perfectly designed our biosphere is, even in its smallest details.
Eisner, T. 2003. “For the Love of Insects”. Harvard University Press. Pg. 1
Holldobler, B.& E. Wilson. 2011. “The Leafcutter Ants”. Pg.11,34.