Cotton Root-knot Nematode, Meloidogyne incognita
The common root-knot nematode (Meloidogyne incognita), also known as the southern root-knot nematode, is a species of roundworm that infects plants. It can be found across the world and infects a number of different hosts. It resides in the root system of the host plant, creating gnarled roots and galls. This species travels through more shallow temperature gradients than other organisms. This is known as thermotaxis and is thought to be the system in which these worms locate the best soil levels. After the worms find the best soil, they can use chemical cues to find adequate root systems to live in and feed upon.
Image Caption: Whiplike larva of root-knot nematode, Meloidogyne incognita. William Wergin and Richard Sayre/Wikipedia