Monday, April 19, 2010

Giant Mosquitoes ?

There’s been concern among some of my neighbors that we are being invaded by giant mosquitoes.

Actually, the spring rains have encouraged the pupation of large numbers of common crane flies (Tipula planicornis). At first glance, these long-legged flies do look like mosquitoes, but they actually have very little in common.

The crane fly larva feeds on roots and plant matter under leaf litter. It kind of looks like a large (half inch long) thick-skinned maggot. It isn’t an attractive childhood, but it is nothing like the aquatic mosquito. Once the crane fly develops into an adult with wings it has a fairly short lifespan and typically does not eat. You can tell it is a fly and not a mosquito because it only has two wings (one pair). Mosquitoes and all other kinds of flying insects typically have four wings (two pairs).

Some people call crane flies “mosquito hawks” with the assumption that they eat mosquitoes. Unfortunately, that is a myth. Personally, I think they look like fairies when they fly up from the grass.

The past year’s warm dry weather followed by a moderate winter with normal rainfall has enhanced grass growth. Crane fly larva prosper in grass and we seem to be having an unusually large population of adults this spring. The females are considerably thicker in body. One source said that females are unable to fly. There appear to be far more males than females, and I saw a group of males mobbing a single female all trying to mate with her.

Is anything eating these crane flies? So far I haven’t seen any birds or other animals munching on the flying adults. If you look at them closely, they are mostly long brittle legs and glassy wings. There isn’t much to eat. However, I’m sure that as larva they are consumed by a number of our yard birds, Bewick’s wren, California and spotted towhee. Perhaps their availability added to the Bewick's decision to nest in our yard. Bewick's wren nest.

So don’t be alarmed by a large long-legged crane fly headed your direction. It isn’t a mosquito and it isn’t going to hurt you. Part of being a good gardener is getting to know the species in your yard. The common crane fly isn’t going to harm you or your garden. In fact I noticed a young alligator lizard sunning itself about a foot from the breeding crane fly group. Maybe it was waiting for the soon to be laid, crane fly eggs.

No comments: