i have had these bites in the past oaccasionally(actually, im not even sure if they are btes, but most likey), and i assume i get the over night, because i dont look at my legs all taht often... they form 3 scabs evy time ive seen them , and are very close together
here they are... hopefully someone can identify the type of insect

http://i188.photobucket.com/albums/z30 5/calv_n/Image002.jpg (two scabs very close together at the top red part)
http://i188.photobucket.com/albums/z30 5/calv_n/Image001.jpg
http://i188.photobucket.com/albums/z30 5/calv_n/Image000.jpg

sorry for poor quailty(camera phone), but you should hopefully be able to make out what it is

thanks