INFO:
     It should be noted, these are often thought to be giant mosquitoes. I used to think so too, but after a little research, I found that these are NOT mosquitoes, nor are they mayflies. They are Diptera Tipulidae, or more comonly known as, the Cranefly. Craneflies are also refered to as Mosquito Hawks or Montana Mosquitoes.
     They may be in the same order as mosquitoes, but these guys are not known to carry disease, can not sting, or even bite. They are completely harmless. Infact, the adults (the group you would see flying around) (pictured above), don't even eat! They only live 2 to 14 days. They're only purpose in life is to mate and lay eggs. Because of they're size, though, they can be pretty intimidating.
     Only when they are still a larve (small maggot like worm) do they cause any detriments at all. During that stage, which lasts about 2 weeks, they feed on the tips of your grass.