Mosquito larva. Light micrograph (LM) of a mosquito (Culex) larva. The larva lies parallel to the water's surface. At the end of the abdomen (top) is a long breathing siphon with an end spiracle. This is in contact with the air, to take in oxygen and cause a current to flow towards the mouth, which then filters out any food particles. Culex mosquitoes inhabit urban or rural areas and usually bite in the evening or at night. They can transmit the diseases encephalitis and filariasis. Magnification: 25X when printed at 10cm.