Together with R.J. Beck of the Tippecanoe County Health Department and two interns, 499 visits were made to habitats that supported mosquito larvae or were suspected of supporting them. The visits stemmed from "call-ins" by the public, reports by city and county streets and parks personnel, and our extensive surveys conducted from roads and on foot.
The rainfall pattern, amounts of rain per rainfall event, moisture content of soil, and periodic flooding of streams influenced the production of mosquito larvae starting in early May and continuing into early October. Flooding of dry land along the Wabash River and Wildcat Creek in mid-May led to hatching of Aedes and Psorophora eggs laid previously and within several days thereafter to tremendous numbers of larvae along extensive stretches of both streams. Aedes and Psorophora larvae also were found in previously dry runoff catch basins, wheel ruts, and numerous ground pools that filled with rainwater. In early July, the drainage basin of the Wabash River and Wildcat Creek experienced very heavy rainfall, including nearly 8 inches of in the Lafayette area, followed by record flooding of dry land along the Wabash River and other streams. This led to a second round of tremendous numbers of Aedes and Psorophora mosquitoes. In the most productive sites along these streams, hundreds of larvae were collected per dip. Larvae of Aedes trivittatus and A. vexans were found in nearly every site sampled and larvae of Psorophora ferox and P. horrida in certain sites. A third round of high numbers of Aedes and Psorophora mosquitoes in flooded land along streams followed nearly five inches of rain the last week of August.
Culex larvae were collected in a variety of standing water habitats starting in early May and large numbers were collected in runoff catch basins that held water for two weeks or longer following the rainfall events in early May, early July, and late August. Larvae of Culex restuans commonly were collected in ground pools and wheel ruts that contained decaying vegetation and in discarded tires, starting in May and continuing all summer. Larvae of C. pipiens and C. salinarius were collected in similar sites starting in mid-June and continuing all summer, with very high numbers in runoff basins containing polluted water following the three major rainfall events mentioned above.