Soldier Termites and Their Wild Helmets
When we think of termites, we typically think of destruction, damage, wood-eating, and good-for-nothing insects. However, termites are so much more than that. Termites are complex insects and one of the few insects out there that can eat wood. They have a uniquely complicated reproduction cycle, and they are one of the truly social, or eusocial, insects out there. One of the qualifications to be “truly social” is to have a developed caste system. This means that different termites are born to do different tasks within the colony. In a termite colony, there are workers, soldiers, and reproductives. The workers make up the majority of the colony and do most of the work for the colony. Reproductives are responsible for mating, starting new colonies, and continuing the current one. Lastly, there are soldier termites. I feel like the soldier termite doesn’t get a whole lot of credit for how interesting they are and how different they can be among the various termite species.
The soldiers, as their name implies, are responsible for the defense of the colony. They are a sterile and wildly impressive member of the colony for their means of defense. They defend by using their head with their exaggerated mandibles; however, depending on the colony the exact method of defense and shape of their head will differ. Research is done by Prestwich in 1984 grouped soldier termites by their defense mechanisms into four categories: phragmotic, mandibular, salivary, and frontal. They were then further grouped based on their ability to chemically or mechanically defend their colony with their head. Prestwich grouped their defense mechanisms into 9 different methods: phragmosis (using the head to plug entry), crushing mandible, slashing mandible, piercing mandible, glue squirting, daubing brush, symmetrical snapping, slashing/snapping, and an asymmetrical snap.
I don’t know about you, but I find it incredible that the tiny termite has such diversity among the various species – not just in how it looks but what it is doing to actually protect the colony. Let’s look in a bit more detail at the different defense mechanisms that soldier termites use. Phragmotic soldiers are soldiers with short mandibles and blunt heads that are used as an effective barrier to block gallery entrances into the wood. Most of the species in the family Kalotermitidae use these mandibles. Crushing is considered a plesiomorphic condition and may or may not have a chemical association. Crushing mandibles are serrated and robust. Soldiers of these colonies are in low abundance and sluggish.
By comparison, termites with slashing mandibles have more slender, straighter, longer mandibles with greater angular motion. Termites with piercing mandibles have slender mandibles that are inwardly curved with prominent teeth. Piercing motions may be accomplished in conjunction with chemicals. Termites in the glue squirting category have what is referred to as mandibular regression, meaning they have developed an ejected terpenoid secretion instead of mandibles. Daubing brush soldiers also have a mandibular reduction, and they defend with a topical application of lipophilic contact poisons. The last three categories are different snapping functions. There are symmetrical snapping termites that store energy in an elastic distortion of the mandible and release it abruptly to strike a percussive blow. They are most effective in confined spaces where the soldier blocks the entry hole. Then there are the slashing/snapping termite soldiers with mandibles that both snap and slash. Finally, the last category would be the asymmetrical snapping termites that have highly elastic mandibles that allow lateral blows to be delivered only to the left.
So the next time you are looking negatively upon our little wood-eating “friends,” just remember that they employ a variety of defenses against threats to their colonies. As we find when we take a look at all insects more closely, insects have a lot of highly developed features that will help them to better function and survive in a world that is much bigger than themselves!
Kristen Stevens, BCE
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