Autothysis means to explode yourself, and not the wimpy way with some device or chemical. Animals that practice autothysis — and they are all insects — rupture their own internal glands or organs with such force that their insides burst through their own exoskeletons.
Why would any creature choose to do this? Well, it's a defense mechanism, obviously, albeit an extreme one. For instance, some ants have special cells in their bodies that carry sticky liquid; the ants access the cells by bending their bodies in have until the cells and the bodies split open. When sprayed, the liquid is meant to seal off an attacker's face. Likewise, there is a whole family of termites called Serritermitidae that, when the nest is under attack, twist their body so violently that they rupture glands which spray a substance capable of blocking off tunnels. The termites basically build an impregnable barricade with their own exploded bodies.
Autothysis is such a good defense mechanism that some termites have turned it into a retirement plan. When young Neocapritermes taracua termites workers hatch, they have small external pouches and small internal salivary glands. As they grow up, gaining skills and strength, the pouches and glands stay small. It's only once they get older that these pouches enlarge. In the pouches are protein crystals that contain copper. The crystals enlarge as the termite falters in its duties. The older workers' salivary glands also go into overdrive, producing a lot of juice.
When the nest gets attacked, the older workers don't run to safety with the rest of the workers. They turn and run up towards the enemy with the soldier ants. When the enemy insects get close, the old workers rupture their internal and external glands, mixing the contents together and spraying them outwards. The mixture is not just sticky and hard to get off, but toxic to other termites. It corrodes their bodies, so they die immediately like space marines that have just stabbed an alien, or they just slowly break down as tiny flecks of the compound wear away at their bodies. The termites, meanwhile, are secure in knowing that only the older, less productive workers are killing themselves off via autothysis.
Which sounds good until it's their turn.