In addition to having an incredibly large number of mosquitoes in Iowa this year, we also have had more questions and inquiries that start out, "I just saw the biggest mosquito of my life!!"
The very large mosquitoes that bite viciously are one of our "usual" species found in Iowa. However, this year is different in that the population seems to be larger than normal. The extra-large mosquitoes are in a genus called Psorophora. There is no customary common name for these mosquitoes, though some references use the term "gallinipper" or "gallinipper mosquito" for Psorophora mosquitoes.
Psorophora mosquitoes are a floodwater species. The females lay eggs on moist soil and the eggs hatch when covered with water from floods or temporary pools and impoundments. The larvae grow very quickly to the adult stage. Some of the Psorophora mosquito larvae are predacious; that is, they eat the larvae of other mosquitoes sharing the temporary pool. There can be several generations of Psorophora each summer depending on rainfall. In the fall of the year the last eggs laid for the season remain dormant and wait for floods the following year. Some references claim the eggs can lay dormant for a long time and hatch years later.
Of the 14 species of Psorophora in North America, the one common in Iowa is Psorophora ciliata, a large mosquito with noticeably-banded legs, pale stripes on the side of the dark thorax, and stiff, erect hairs along the legs. Females of Psorophora ciliata are vicious biters and prefer to feed on mammals. They will bite during both the day and night and are able to bite through heavy clothing. (That's just nasty.)
There is nothing special for the control of Psorophora mosquitoes. The usual homeowner/gardener actions of eliminating breeding sites such as bird baths, plugged rain gutters and old tires may help reduce some kinds of mosquitoes, but not Psrophora that are breeding in flooded fields. Personal repellents remain the best defense against biting. See the article on repellents in this newsletter.
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