Head back to Sanctuary to receive this quest from Sir Hammerlock. He wants you to do some research on an insect known as a varkid. When the creature takes enough damage it goes into a cocoon and evolves into a different, more powerful form. He gives an evolution injector to hit the eggs with as the insect transforms.
Head to Tundra Express to find varkid nests. The nests aren’t far from the entrance to the area so finding them should be fairly easy. You’ll need to use a weaker weapon on the insects to insure they don’t die. Once they receive enough damage the creatures will go into their cocoon to morph. Run up to the cocoon and use the action button to give them a dose of the serum. This also turns it into a badass version of itself (thanks Hammerlock). Kill the creature quickly with an incendiary weapon to prevent it from killing you and allowing you to receive the sample.
Hammerlock needs four samples, which means doing this three more times. Once you’ve collected all of the samples head back to Hammerlock in Sanctuary and receive your reward for once again endangering your life for the sake of his research.
Item: random SMG