Twilit Bloat
This is seemingly the queen of the Shadow Insects and also a mini-boss. Link needs to defeat this beast in order to restore the light to the Lanayru Province, as this monster holds the last tear of light.
To defeat it, Link must wait until it isn't charging him or is bursting with electricity. L-target it and leap onto its lower section. Keep a hold of the L button and repeatedly press A to bite it furiously. Repeat these steps a few more times and it will eventually fall into the water, lying on its back. Jump on its belly and use the energy field with Midna's help to attack its six tentacles at the same time. Once they are all destroyed in the same instant, it will shrivel up and die. This will release the last tear of light Link will collect, allowing him to return light to the province.