The term 'pesky biter' can be broken down into two crossword solutions: GNAT (4 letters) and skeeter (7 letters). A GNAT is a small, flying insect that is known for biting and annoying humans. They are usually found in warm climates and are attracted to light. A skeeter is another name for a mosquito, which is a type of flying insect that is known for its ability to spread diseases such as malaria and Zika virus. Mosquitoes are also known for their annoying bites and buzzing sound. Both gnats and mosquitoes are considered pesky biters.