Chiggers are actually baby mites. Since they are too small to be seen with the naked eye, I won’t describe them except to say they are ugly. The adults, which can be seen, feed only on plants and are not a problem for us, except that they lay eggs to make more baby mites.
Now a baby chigger wants to become an adult chigger, and to do so it needs a high protein meal like humans or some other mammals. This requires a lot of patience and fast reflexes. Chiggers hang around on grass or bushes and wait for something to walk by. When they sense air movement or a whiff of carbon dioxide that tells them something is nearby, they grab on and climb aboard. They will then poke around looking for a good spot to feed, preferring warm, damp places where skin and clothes are close together, such as waistlines or under socks.
Their feeding habit is a little unsettling. They spit on your skin, which contains a protein-digesting enzyme that turns some of your skin into a small blob of predigested food. The chigger then sucks this up, smiles, and then starts over again. It does this spit and suck routine over and over again on the same spot, until it gradually makes a small hole down into your skin.
At first this doesn’t bother you, because your top layers of skin cells are dead. But after a while they dig down to some live cells, which get irritated. Your skin cells treat this feeding action as an invasion and try to build up a defensive wall around the hole, resulting in a swollen red spot that itches.
Meanwhile, the chigger has grown bigger and fatter and may become visible in the middle of the red bump. At this point chiggers are often killed by your scratching. If not, they will soon drop off, having stored away enough food to grow into adults. Unfortunately the red bump continues to itch for days after the chigger is gone.
Avoiding chigger attacks is not easy, since they can be almost anywhere. Applying an insect repellent containing DEET is usually effective. Chiggers tend to congregate in tall grass and weed areas, so you might steer clear of those places. These grassy areas usually grow a pretty white flowering plant with lacy leaves called Queen Anne’s lace, which most folks around here call “Chigger Weed”.