Mandibles Unknown
Insects are absolutely incredible. Unfortunately, most people are too busy trying to get rid of them to notice this. Let’s pause for a moment to observe just one aspect of insects. We will look at one simple part of insects, their mouths. Specifically, their mandibles. Yes, insect mouths may not sound enticing to most but stay with us here. It will be worth it. In doing so, you will hopefully gain an appreciation for just how incredible these often-overlooked creatures are and learn a few things in the process. For those of you who flip past Animal Planet when channel-surfing, allow us to fill you in on what exactly a mandible is.
Insects generally have four main components of their mouth, the labrum, labium, maxillae, and mandibles. With the exception of butterflies and moths, all insects have these general structures. However, they are distorted to all sorts of sizes and shapes to accomplish different tasks. The labrum is the top; the labium is the bottom. Maxillae are a pair of arm-like structures that help insects pull food into their mouth. Still with us? Good, let’s carry on. The part that we will focus on is the mandibles. These are what come to mind when most people think of insect mouths. These are the creepy, pincer-like mouth parts that haunt people’s nightmares. They are found between the labrum and labium, and these are one of the coolest features on insects. The diversity of shapes and sizes these parts can come in is astounding, and the crazy ways insects use them is even more amazing! We will look at some examples, but let’s take a moment to consider our own anatomy.
Humans are industrious creatures. Vital to accomplishing this industry, hands are one of our most important traits. We use them for almost everything, and we often take them for granted. Most of our less fortunate friends, insects, do not have hands or even front legs capable of grabbing. Instead, they are forced to build their houses, gather their food, and care for their young with nothing but the pieces of exoskeleton that extend from their mouths. Think about that next time you grab a door handle, scratch an itch, or tie your shoes. Now, let’s look at a few examples of insects overcoming this issue, among others, with their mandibles.
Ants are one of the most notoriously overlooked insects. When we want to describe something insignificant, we will often liken it to an ant. This is totally undeserved. An ant’s mandible consists of an external margin, a masticatory margin, a basal margin, a basal angle, and teeth (don’t be scared by the terms, just look at the picture below).
Most ant mandibles have evolved to be short and curved but more recognizably have a long masticatory margin and noticeable basal angle. All this combined gives their mandibles a characteristic triangular shape.
These ingenious works of engineering allow ants to have extremely interesting behaviors. For example, when ants go hunting, they use their mandibles to decapitate their fallen prey. Imagine walking up to ants swarming something like a grasshopper and seeing them decapitate their prey, often many times their size, with nothing but their mouths. That would be like a human trying to decapitate an elephant that has a hard exoskeleton. That would be tough to do at all, let alone with nothing but your mouth! There are even differences in mandibles among ants of the same species. For example, soldier ants within colonies have bigger body sizes as well as larger mandibles. These mouth parts have even evolved in specific ways to either defend against or attack other ants. For example, a type of ant called a slave-making ant has sickle-shaped mandibles specially designed to kill other ants. They will actually hunt down the queen of another ant colony and use their specially-designed mandibles to assassinate her, taking over the colony afterwards!
Let’s take a look at an order of insects called Hemiptera. This includes insects called “true bugs”. Insects in this order possess a characteristic modification to their mandibles that allows them to pierce and suck. Their mouth looks entirely different from ants, but it is composed of all the same parts! In these insects, their mandibles are actually enclosed by the labium. This forms a sort of tube that they can stab into objects such as fruit. The modified mandibles and maxillae in this type of mouthpart are called stylets.
A particularly eerie example of this type of mandible is the assassin bug. It turns out they are aptly named, as they prey on other insects. One deft stab with their spear-like mouthparts is enough to spell the end for their prey. They inject a venom that paralyzes their prey and begin to suck out the insides through their tube-shaped proboscis. This venom is pumped through one of two channels formed by the maxillae. As you can probably guess, the innards are sucked up through the other channel. This complex process is aided by the mandibles, which can slide in and out of the channel formed by the labium. They cut into the insect and allow further insertion of the proboscis. Who would guess that this level of ingenuity can be found right in your backyard?
As you can see, there is a great deal of variety amongst insect mandibles. These examples barely scratch the surface; we only looked at two types of insects! Next time you go to squish an insect, take a moment to observe its mandibles instead. See if you can identify some of the other mouthparts as well! Insects are incredible and deserve to be appreciated for the stunning, resourceful creatures they are.
Sources:
https://australianmuseum.net.
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Take a look at the four main
mouthparts as
they appear on a grasshopper.
https://insectmouthparts.weebly.com/morphology.html
|
Humans are industrious creatures. Vital to accomplishing this industry, hands are one of our most important traits. We use them for almost everything, and we often take them for granted. Most of our less fortunate friends, insects, do not have hands or even front legs capable of grabbing. Instead, they are forced to build their houses, gather their food, and care for their young with nothing but the pieces of exoskeleton that extend from their mouths. Think about that next time you grab a door handle, scratch an itch, or tie your shoes. Now, let’s look at a few examples of insects overcoming this issue, among others, with their mandibles.
Ants are one of the most notoriously overlooked insects. When we want to describe something insignificant, we will often liken it to an ant. This is totally undeserved. An ant’s mandible consists of an external margin, a masticatory margin, a basal margin, a basal angle, and teeth (don’t be scared by the terms, just look at the picture below).
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a: external margin, b: masticatory
margin, c: basal margin, d: basal angle, e: teeth.
http://tolweb.org/treehouses/?treehouse_id=2482
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Compare this slave-making ant’s
mandibles to those seen earlier.
These are both ant mandibles, but they are so
different!
http://www.bbc.com/earth/story/20151028-a-few-spe
cies-of-ant-are-pirates-that-enslave-other-ants
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| This
is a cross section of the tube-like mouthparts of a true bug. http://www.wlgf.org/wildlife/hemiptera_intro |
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Look at that menacing, red
proboscis on this assassin bug!
http://entnemdept.ufl.edu/creatures/trees/wheel_bug.htm
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As you can see, there is a great deal of variety amongst insect mandibles. These examples barely scratch the surface; we only looked at two types of insects! Next time you go to squish an insect, take a moment to observe its mandibles instead. See if you can identify some of the other mouthparts as well! Insects are incredible and deserve to be appreciated for the stunning, resourceful creatures they are.
Sources:
https://australianmuseum.net.
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