By James A. Bethke.
Every spring I get calls and emails from people about the great mosquito eaters that are showing up at their lights, windows and doors at night. Figure 1 is a photo of just one of the very many that found its way into our home this last spring. They go by many names such as mosquito eaters, mosquito hawks, or daddy long legs. People tend to confuse them as giant mosquitoes or think they actually eat mosquitoes, but none of that is true. They are actually called crane flies (Order: Diptera, Family: Tipulidae).
There are more species of crane flies (>4000 species) than any other group of flies described so far. Some adult crane flies (Figure 1) feed on nectar but most do not feed at all. They emerge as an adult, mate, lay their eggs and die. The adults are very fragile and tend to release their legs when threatened. I have some experience with this because my wife wants them immediately removed from the house when present, and when I grab it, it usually ends up being a crane fly with two less legs. They make good food for pet lizards or spiders of your sons and daughters. Adult crane flies can get quite large, from leg tip to leg tip can be as much as 3-4 inches in tropical climates. We have a local species that is easily 3 inches leg tip to leg tip. I’ve collected some of these big ones in southern California, but when I put them in my collection, they usually end up being a crane fly body and a pile of legs in the bottom of the box.
One caller a while back wanted to know what was causing so many of them this year. Like any other organism, there are booms and busts in their population dynamics caused by abundance or lack of food supply, occurrence of natural enemies, or some other natural factor. In addition, exceptional conditions may occur locally causing a local event. This is true for most insects and other animals in our area. Where I live, we had such an event about 5 years ago where the numbers of crane flies were exceptional. It continued the following year, but it hasn’t happened since then. I suspect it will happen again at some point. It’s a natural cycle.
The immature form, like other flies, is called a maggot, but the larger crane fly species maggot also goes by the name ‘leatherjacket’ because they look like their skin is made of leather, dry and thick looking (Figure 2). They typically live in and feed on the duff or leaf litter or other organic matter, and I recently found them living in the duff under our cape honeysuckle just outside our raised gardens.
Crane flies can actually be a pest insect. It’s too arid here, but the European crane fly is a serious pest of turf or lawns in the wet northwest. They are also considered an occasional pest of tobacco production on the east coast. For those of you interested in trivia, there is information about European crane flies as pests of potted marijuana in Denmark (Hemp Diseases and Pests: Management and Biological Control by John Michael McPartland, Robert Connell Clarke, David Paul Watson). Oh well. It might be good information since CA has conditionally legalized marijuana production. By the way, if you need help with your marijuana crop, I’m sure there is an Extension Adviser that can help you. I only cover floriculture and nursery ha-ha.
I remember a Master Gardener telling me once that there were so many of these big mosquitoes around her house at night, she was afraid they would sneak in and suck them all dry before dawn. She was kidding of course… she really was… I think. If after you read this and you still believe you are going to die by Crane fly, bug zappers will work for those of you that find satisfaction from the occasional ZAP that you hear when a bug finds its unfortunate end.
James A. Bethke is the Floriculture and Nursery Farm Advisor Emeritus for San Diego and Riverside Counties. The Floriculture and Nursery Farm Advisor Emeritus conducts applied research, education and outreach programs to improve production and viability of the floriculture and nursery industries in San Diego and Riverside Counties. Jim's program emphasizes the integrated pest management of major pests of floriculture and nursery production. He collaborates with regulators, growers, and other scientists on advisory committees that set policy based on science.