Question
Hi Jim. We have noticed alot of holes throughout our back yard, some tiny and some the size of a quarter and at least 12 inches deep.  There doesn't seem to be much dirt surronding the area (like an ant hole would have).  Do you have any idea what insect would do this? I have tried to see what comes in or out but there isnt much activity (at least not during the day).Last summer I did notice a large amount of flying insects (kind of like flies but smaller) all over my hydrangea bushes. Any info you have would be great. Thanks.

Answer
Sounds like the holes made by emerging cicada nymphs. Their tunnels can be very deep. These insect emerge and fly to nearby trees. The hole will soon fill in and there is no reason to treat since the insect has gone.
If it were later in the season i would also think that some of the holes were from a wasp called a cicada killer. They live single and kill cicada nymphs and drag them into the hole. If there is fresh soil around the hole it maybe the wasp. These solitary wasps may become a nuisance when they dig holes in lawns kicking out a six to eight inch diameter horseshoe-shaped pile of dirt (mound) around the nest entrance. Males have especially aggressive territorial behavior, but have no sting. Females are difficult to provoke, can sting, but rarely do. The female wasps are not aggressive and control is rarely needed except in unwanted places. Usually it is not necessary to control cicada killer wasps unless their presence is a nuisance. Sometimes these wasps can be troublesome in high traffic home and commercial areas such as berms around swimming pools, near planters at door entrances, flower beds, golf course greens and tees, and other unwanted areas. Sometimes they may fly erratically near people, causing fear. Males may actually defend their territory by dive bombing people's heads and shoulders! One can apply bendiocarb (Ficam), carbaryl (Sevin), or diazinon dust onto each nest entrance if the infestation is not too widespread. Do not disturb the burrow as the female must walk through the dust in order to get a challenging dose of the insecticide.

But since it is early for the wasps I would think it was cicadas.