If insects could talk – English preferably! – I would like to ask them what they think is the key to their great success! In particular, I would like to ask a member of each Order of insects, to describe the main innovations and adaptations which have led to the success of their particular group. Since they cannot speak for themselves, I have tried to imagine in this blog what they might say! N.B. I use words like ‘designs’, ‘plans’ and ‘innovations’ as if they were like successful products or brands, as a literary device; not that I really believe that they were designed; natural selection is blind, but inevitably builds on previous structures and features.
I should mention, by way of introduction, that all insects have benefited from some basic engineering and design features which were developed in the distant past. We won’t explore these in detail here, but they include: an exoskeleton, a segmented body, paired jointed appendages, vision, the ability to smell and taste, and so on. I am sure that if they could speak, they would thank their ancestors for the hard work and evolutionary selection that went into these basic structural and physiological design features. Insects could not have done it without those who went before them!
Many of the characteristic insect types we are all familiar with have been around for a very long time. The first insects probably appeared in the Ordovician, some 475 million years ago (mya), although the first fossil (a springtail) dates from a bit later, c. 400 mya.
As there is so much ground to cover, we will not spend too much time on these primitive wingless insects (such as springtails, bristletails and firetails), whilst acknowledging that they were the first to come up with a number of key innovations – such as long, tail-like cerci, flat body scales and much else – that were picked up and further developed by some of the other orders which came along later.
Wings and flight
The first flying insects appeared during the later part of the Early Carboniferous, I think? How flying evolved is still a matter of debate. Some say it happened as forests grew larger and insects climbed trees; jumping off and gliding down on proto-wings would have given some of them a huge advantage. Maybe they climbed up to the top of plants and trees to warm up? The world grew colder during the early Carboniferous. There are lots of other ideas about how wings evolved (see Shaw, 2014), but one thing is certain, once they appeared, wings became quite common in a number of insect orders. It was clearly a huge advantage to be able to fly, for all sorts of reasons, although later on, some groups decided to do without wings and to peruse more specialized wingless life styles.
“Look we invented wings! We don’t get the credit we deserve, but without our invention, nobody would be flying today! We come from way back; we’ve seen it all, and survived everything that has been thrown at us: cataclysmic eruptions, climate change (you think you have seen climate change, what a laugh!) meteorites, you name it. Not all of us survived, but we are still here. Some people call us old fashioned, but we don’t care. Let’s see if you are still around after 250 million years!”
Odonata (dragonflies and damselflies)
“We dragonflies often look back and marvel at our ancestors who lived in the Carboniferous, well over 300 mya. They were huge animals, the largest insects who ever lived, with wingspans of up to 75 cms. It was a strange time, with very high oxygen levels which helped them breed, and also an absence of pesky birds, which sometimes make our lives a misery now”, said the dragonfly. “Some of those old dragonflies would show the bee-eaters a thing or two! There were also no bees, wasps, ants and other Johnny cum lately insects back then”, sighed the dragonfly.
“Our little damselflies can trace their origins back even further than the dragonflies, right back to the Permian period. One thing that really helped us survive many of the upheavals we have faced in our long lineage, is keeping our young ones under water”, said the damselfly. “By developing gills and living in freshwater ponds and rivers, our larvae have been able to sit out some of the terrible disturbances that have happened up here in the open air”, she said.
Orthoptera (Grasshoppers, crickets, katydids)
Another ancient order, the Orthoptera originated in the Carboniferous period (c. 350–300 mya), but many existing types evolved more recently, such as: katydids (superfamily Tettigonioidea) during the Cretaceous period (c.145–65 mya). The members of this order rightly highlight their outstanding jumping ability:
“Our large, muscle-packed hind legs (below) enable us to leap incredible distances and hence escape from predators that many other insects would succumb to”. They are also wonderful songsters, and some of them (crickets) have come up with the rather unusual idea of having ears on their knees! In truth, different insects have placed their ears all around their bodies, from their antennae (fruit flies) to their knees (katydids)!
Phasmatodea (stick insects and leaf insects)
“We are the masters of mimicry! We first appeared during the Triassic period, the age of dinosaurs, and we quickly learnt how not to become velociraptor food. Our ancestors had to think fast, and came up with thousands of new designs to help us blend in with the vegetation. Some of us opted to look like sticks and branches; others preferred to mimic leaves; but we have had to keep up with the ever-changing vegetation over the millennia!”
“We would also draw your attention to our artistic abilities as well, for example we produce a range of beautifully sculptured eggs, that would be the envy of your famous designer, Fabergé!”
Grylloblattodea (Rock crawlers, ice crawlers)
“We are a small and insignificant family, compared to other orders, with only about 30 species, but we are very good at living at low temperatures – 1 deg C is just right for us – so we are most happy on the tops of mountains or even on glaciers! We did have to give up wings when we moved up onto higher ground. We were losing too much heat through them, and we get on fine without them!”
Mantophasmatodea (Heel walkers)
“We are another rather insignificant little group, with only 20 species, but we still find it very funny that you humans only noticed us in 2001! We have been here for so much longer than you, and watched you come down from the trees in east Africa; you never even noticed us! Ha, ha, ha!”
“You only have to look at us to see that we are the Swiss army knife of the insect world! We have developed the cerci that some of our ancestors had, into a formidable pair of forceps, or pincers. We use these for a whole range of purposes, from catching prey to fighting or defending ourselves. Our ladies like a man with a good pair of pincers!”
“We are closely related to the Zoraptera and Embioptera, and go back a long way; to the Lower Permian period. We have not changed much over time, and like to stick to what we know; living under water in our early stages, and not eating much when we become adults! That’s why we are so slim!”
“We are small and insignificant, and there are very few of us (44 species) but we are very good at living in rotting wood and feeding on fungi. We don’t like the limelight and prefer to be left alone to carry on with our work. We are sociable and like to think we do a good job breaking down plant material. That is probably why we have survived and thrived in our own little way for so long.”
“Well, there are lots of things that make us special, but we are very proud of the symbiotic arrangements we have forged with other organisms, bacterial, fungal and protozoan, all to our mutual benefit. Some of our oldest species forged relationships with flagellate protists; welcoming these organisms into their guts, which enabled them to break down cellulose and opened up a whole new food source for us. The single cell (Trichonympha) gut symbionts say that they are very happy with the food and shelter we termites provide them. A real win/win situation I ‘wood’ say!” Said the termite, laughing through his mandibles.
“The other thing we are very proud of as well, is inventing air conditioned homes. Our mound-building members have produced some fantastic structures that are the envy of the insect world. The occupants live in comfortable, ventilated sky-scrapers (below) and enjoy a standard of living well above that of other organisms forced to live outside in hot climates, in places such as Africa and Australia. You humans took a long time to catch up with us, and you are still learning frankly!”
“Some people have been saying lately that we are not a true order, and should be placed in with the Orthoptera! What a cheek! We like to think that we are so distinctive, with our wonderfully adapted forelegs, that we certainly deserve our own order! No other insects come close to us for being able to suddenly seize a prey item; to snap forward our spiny forelegs and grab hold of our next meal. We also treat our ladies with the utmost respect. Otherwise they will bite your head off!”
“Like the Odonata, our heydays were probably in the Carboniferous era. Some of our members are still doing very well, and have spread all over the world, thanks to you humans. Don’t call us dirty! It’s you who drop all the food; we just clean it up!”
“We are another small group that has been around since the mid Jurassic. We like hot, tropical places, where we live on rocks or tree bark. We are very good at spinning and weaving using silk, which we produce from a gland in our leg. We know that there are other insects who make silk, but we make the best, finest silk in the world! What’s more, all of our young ones can produce silk as soon as they hatch out. We make the most extensive, well-made, tent-like galleries in which we live. We are the Kings and Queens of silk weaving.”
Hemiptera (True bugs)
This is such a huge order, and as to what we do best, it would really depend on who you asked. Water striders or pond skaters, are of course, very proud of their ability to walk on water. “It took us a long time to perfect the art of pond skating – walking on water that is – and many lives were lost before they were able to skate across the surface of ponds and rivers with the speed and agility we can today. Unfortunately, the patent was stolen early on, and some other orders managed to perfect the trick, but not nearly as well as us”, said the gerrid.
“As a so-called ‘true bug’, I would say that our liquid-feeding, piercing mouthparts – which can be manipulated deep inside a plant – are probably our best feature, and one we came up with a long time ago (in the Permian period)” said the aphid.
“We thrips came up with a totally new type of feeding strategy, which no other insect had thought of at the time; I’m talking about the end of the Permian period. The Hemiptera had already patented their piercing-sucking mouthpart design, so we decided to try something else. We came up with a type of liquid feeding method using one mandible as a sharp tooth. We scratch the surface of plants and then suck up the liquids which ooze out using another device we invented: a fluid sucking beak. These breakthroughs – you could call them beak-throughs! ha, ha ha! – have kept us going strong for about 250 million years! Beat that humans! Our small size and feathery wings have also been a great advantage, although there are a few other orders with insects who have feathery wings like ours. They are great for swimming through the air; which is what it feels like when you are as small as us.”
Psocoptera (Book and bark lice)
“We are an ancient order that arose in the Permian period, 295–248 million years ago. We are not a big order (5,000 species) and we keep a low profile, mostly scavenging food and feeding on tiny plants. We like to think we do a good job cleaning up and keeping things in order. You would notice the mess if we weren’t there! Things would really start to pile up!”
“Tell the humans about how we give birth to live young just like they do” said another psocid.
Metamorphosis: Insect metamorphosis appears to have originated in the early Devonian, c. 400 mya. At first, these changes were what we call incomplete metamorphosis (hemimetaboly), where the basic adult body plan is laid down during the embryo stage, with growth occuring in a series of nymphal instars without any marked changes in form and structure; the wings and genitalia finally appearing during the adult molt.
Complete (or holometabolan) metamorphosis first appeared in the Carboniferous, c.350 mya and is an astonishing innovation, from which all ‘modern’ insects benefit from. Here the adult body plan is created in the pupal stage, rather than during embryonic development, which means that there are two very separate and highly specialized body plans for the juvenile and adult stages. The larval, or caterpillar stages, are optimized for feeding and growth, whilst the adult stage is designed for dispersal and reproduction. This incredible innovation is one of the main reasons why insects have become so successful and account for most of the species on the planet! What a brilliant idea they came up with!
“Well, we have been around for over 270
Neuroptera (lacewings, antlions, owlflies)
“We are also an old order, with some ancestors tracing their roots back to the Early Permian, maybe as long ago as 295 million years” said the ant-lion. “We are hunters and have learnt many skills; we know how to sit and wait for our prey, but we are also deadly active predators when we need to be. I suppose the large, piercing sucking mandibles of our larval stages are our best feature, but we are also good at camouflage and have great eyesight! We also invented silk production, but we rarely get any credit for that!”
Raphidioptera (snake flies)
“As you can see, we have wonderfully elongated ‘necks’ – something we call a prothorax. It was invented in the Lower Jurassic and it has given us the edge in catching and eating insects”.
“You call us snake flies” said another. “But I should point out that we were here before snakes came along!”
Hymenoptera (ants, wasps, bees)
“We are one of the largest and most diverse of all the insect orders. Some of our oldest members can trace their ancestry back to the Triassic, although many of us are somewhat younger, originating in the Cretaceous; but we still remember giving dinosaurs a nasty sting if they got in our way! We have come up with a host of novel features: our stings of course!; and long flexible ovipositors which can place eggs within other insects deep in a plant or tree; plus all sorts of social arrangements which place the needs of the group above that of the individual”.
“I could go on” said the wasp. “I haven’t even mentioned all the cunning ways we invented for living on, and in, the bodies of other insects! Plus our incredible artistic and architectural skills, in making homes out of wood, or mud, for example. But that’s enough for now, I think.”
Trichoptera (caddis flies)
“We are world famous for our case making!” Said the caddisfly. “Our larvae can make a home out of anything; sticks, stones, plant bits, tiny snails, you name it!” Anything you care to give us! We will make a nice little case. We have been doing it for over 230 million years ago, so we have had a long time to hone our skills!”
Lepidoptera (moths and butterflies)
“One of our greatest innovations was of external leaf-feeding caterpillars; something we came up with in the Cretaceous, only 90 million years ago. We really took advantage of the new plants that appeared from then on, and we became very skilled at breaking down all the chemicals that the plants invented to try and stop us eating them!”
“Oh, tell them about out beautiful wings!” said the butterfly. “They are such multi-functional devices. We can warm up using them; the spots and patterns can be used to frighten or fool predators; and we use some of the elaborate designs and ornamentation to impress our mates”. I think they are our best feature.”
“Do you really need to ask?!” said the flea. “We are the best jumpers in the world! I expect those grasshoppers and crickets told you that they came up with it first! Oh yes, and we are very good at living on (and off!) others. Please don’t judge us; if you will have such soft skin! We started feeding off your mammalian ancestors in the Cretaceous.”
“Our defining feature is our wonderful ‘beak’ which has biting and chewing mouthparts at its tip.”
“And we have been around since the Early Permian” said another scorpionfly. “Before most of the other insects you have been talking to existed!” said another.
“Yes, we know we are a bit weird” said the Stylops fly. “Our larvae live inside other insects and out females never emerge, but that’s the way it is.”
“We keep ourselves to ourselves” said the Stylops. “It’s not a lifestyle that would suit most insects, but we like it, and we like to think that we play a part in keeping some of the other insects in check”.
“We like to think of ourselves as among the most modern insects, although the Hymenoptera may disagree! Some of our venerable members can trace their ancestry back to the late Permian period, but we did not really get going until about 240 mya. Some of our younger species – they like to call themselves True flies (what a laugh!) did not arrive until the last 66 million years; some are still evolving. We can do all manner of interesting things, but our main claim to fame is that we only use a single pair of wings to fly. We discovered that we could easily fly with just one pair of wings, and things were improved massively by the invention of gyroscopes. It was very easy to switch our hind-wings over to a pair of halteres – once we had worked out what genes were involved! The Strepsiptera stole the idea though, although I expect they will tell you a different story!”
Of course, many ‘designs’ were independently developed by different orders, working by themselves but coming up with the same thing, as an elegant solution to the same basic problem. In some very long-lived orders, certain designs went out of fashion; indeed they were completely forgotten about, only to be reinvented down the line. Undoubtedly, there was a little pilfering here and there, with suspiciously similar designs or management practices (compare ants and termites for example), appearing in completely separate orders, but these are mostly judged to be independent innovations rather than being the result of copying or pilfering trade secrets. The production of silk (found in the Lepidoptera, Embioptera, Psocoptera, Neuroptera and Trichoptera) is one such case in point, as is the use of gyroscopes (halteres) to control flight (used by both Diptera and Strepsiptera). There are also some orders, which went right back to some of their ancestors, to copy designs, such as preying mantis (Mantodea) which got the basic idea from scorpions (or so it is suggested!). We can’t really complain about this widespread borrowing of ideas, because we mammals have ourselves copied many of the ideas invented by insects, long before were even a twinkle in a synapsid‘s eye!
P.S. I do of course believe, in evolution by natural selection, like nearly all biologists. I have used words like design and development here, simply as an artistic device, to give a different, hopefully entertaining light, on things like convergent evolution, parallel evolution, atavism
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