Litinsects

Dragonfly wings Dipteran (fly) wing Monarch butterfly wing Lacewing wings Litinsects #34: Insect Wings Let’s talk wings. The ability to fly has existed in only 4 groups of animals: birds , bats , pterosaurs , and of course insects . The first three groups, all vertebrates, each evolved flight independently (in other words, they have no winged ancestor in common) and the wings replace a pair of limbs. Insect wings on the other hand, which first showed up around 400 million years ago, are not derived from legs but are completely separate structures. The big debate about the evolution of insect wings is whether they developed from pre-existing structures (like gills or extensions of the thorax) or were entirely new structures. There is very little fossil evidence documenting this evolutionary transition so no one has yet definitively answered this question... Insect wings attach to the second and third thoracic segments. At rest they may be held vertically over the back, horizontally ou...

Litinsects #21: Complete vs. Incomplete Metamorphosis Welcome to METAMORPHOSIS PART 3: Let’s start with a recap of my last two posts... Within winged insects (or PTERYGOTES), there are two different developmental strategies: HOLOMETABOLOUS insects undergo complete metamorphosis with 4 stages: egg, larva, pupa, and adult. All stages look completely different from one another HEMIMETABOLOUS insects undergo incomplete metamorphosis with 3 stages: eggs, nymph, and adult. The nymphal stages physically resemble the adults Nymphs of hemimetabolous insects typically share the same food and habitat as adults and exhibit similar behaviors whereas holometabolous insects usually look different, display different behaviors, and occupy different habitats in each life stage. The takeaway here is that holometabolous insects are very good at compartmentalizing certain tasks into different life stages, in order to reduce or eliminate competition among life stages! Th...

Litinsects #12: Batesian Mimicry Taking a look at this picture, what is the first insect you think of? I’m sure many of you said a bee. But if you look closely, you’ll notice that this is actually a fly! (Only two wings!) In fact this fly exhibits a form of mimicry in nature known as BATESIAN MIMICRY.  This is named after Henry Walter Bates, who noticed the phenomenon while studying butterflies in the Brazilian rainforest. Some species were so similar that he initially could not tell them apart but looking at them more closely, he realized they were not even closely related As we know, many organisms have evolved chemical or mechanical defenses to avoid predators. This is often advertised through APOSEMATIC SIGNALS (bright coloration = stay away from me, I’m dangerous!). In Batesian mimicry, a MIMIC copies the coloration of a MODEL’S signal, thereby telling predators to “stay away” although they really don’t have any defenses In the case of these flies, they ha...

Litinsects #7: Halteres Let’s talk about nomenclature for a second... Lots of species’ scientific names are composed of Greek words that somehow describe the group or a defining feature of the group. A bunch of insect groups include the ending –ptera because, you guessed it, most insects have wings! The scientific name of flies is DIPTERA, which should be relatively easy to decipher... it means TWO WINGS! But wait a minute, you may be saying to yourself, all winged insects have 4 wings right?! Yes they do, BUT o ne pair of wings can sometimes be modified into other structures. If you remember from beetles 🐞 , the forewing has been modified into elytra and they use only their hindwings to fly. Well in flies, the hindwings have been modified and they use only their forewings to fly. The second wing pair has been reduced to small structures called HALTERES. Halteres oscillate rapidly during flight, detecting rotations and perturbations. Flies use sensory info...

Litinsects #3: Compound Eyes I spy with my little eye. Eyes have evolved independently numerous times, which is why they vary so greatly in form and function depending on the organism (notice how I said organism and not specifically animal...? Well it depends on how eyes and sight are defined but animals are not the only life forms that can “see”).  Insects 🐝 and their close relatives the crustaceans have COMPOUND EYES, which are these multi-faceted eyes that you’ve probably seen in flies... So how do they work? Compound eyes are composed of units called OMMATIDIA, which are usually hexagonal in shape. A single ommatidium is like a mini eyeball: it contains photoreceptor cells, a lens, pigments, and an axon bundle that provides the animal’s brain with a small section of the picture that’s in front of it. The brain puts together the visual information from all ommatidia, forming just one image. So flies don’t actually see the world as a kaleido...