Under a magnifying glass, they are seen to have two eyespots which gives them face-like features. They are so slow moving that it seems very unlikely that they could capture a fast moving mosquito larva. However, when a planarian worm senses the presence of a mosquito larva, the worm begins to lay down trail of extremely sticky slime. The mosquito larva becomes stuck when it touches the slime which permits the flatworm to have a mosquito larva for dinner. I've also heard about nematode worms that kill mosquitoes.
Nematodes are very small round worms and are commonly called eelworms.
There are thousands of species of nematodes and they earn a living in a variety of ways. Some nematodes consume decaying vegetable material, and some are parasitic on living plants, insects, and other forms of animal life. Most multi-celled plant and animal species have one or more species of round worms that attack them. Although nematodes at one time appeared to have potential for mosquito control, their useful value has proven to be very limited. A large Toxorhynchites larva can eat more than 20 per day and about will consume 300 in its lifetime.