The larvae...seed ticks. I know a bit about them. Secuono's image is pretty close but IMO, they are even smaller. Just a bit bigger than a chigger and just as aggressive. When we first moved to this area, (1964) it was all open range..the whole county and people ran thousands of head of cattle and hogs in the National Forest that surround this property. Ticks (and grubs) were horrible. You couldn't walk thru any brush or grass without getting covered with seed ticks, even tho we dusted our boots and jean legs with powdered sulfur and tied diesel soaked rags around our boot tops. I don't think any of it did a bit of good. I've seen them moving up my legs as one big cloud, and spent every night in a bathtub with bleach water in it to kill and dislodge them. When you got out, the water would be covered with them--thousands of them. I was a teenager still in school, and was embarassed to go to gym class because my ankles and legs were just one mass of red spots. Underarms and 'other places' nearly as bad.
They did a number on the cattle too. Them poor things wanted to just stay standing in water most of the time and dogs were miserable.
A few years later, the county enacted a stock law and the ticks abated somewhat, but didn't go completely away until fire ants moved into this part of Texas. I haven't seen a seed tick in many years now. There's still some here of course, but they tend to stay up in higher vegetation and not low to the ground.
(I'll be happy to send you a 3lb coffee can full of fire ants and a couple of queens if your extermination procedure doesn't work, but it may be a case of the cure is worse than the affliction)