Goals of the Study
Because of the medical importance of the spider, we hope a more precise understanding of their distribution in Iowa and Illinois will help professionals and the public avoid misidentifications and therefore misdiagnoses which could delay proper treatment for other medical conditions. Our study aims to more precisely document where the brown recluse lives in northern Illinois and southern Iowa.  To accomplish this, we are requesting the participation of as many interested parties as possible to send us spiders for identification. 

Current Knowledge of Recluse Distribution in Illinois and Iowa
The brown recluse is common in southern Illinois and becomes less common as you travel north. The recluse is occasionally found in homes in central Illinois but records north of Peoria are very rare.  A few isolated brown recluse specimens have been recorded from the greater Chicago metropolitan area and southern Wisconsin.  Only two localities in the Chicago area (single buildings) have been confirmed in the past 5 years. 

In Iowa, recluses are not common in any part of the state but they have been recorded in southern counties and rarely as far north as Ames.  Cold winter weather may limit the northern distribution of recluses in the wild in both states, although recluses accidentally transported to climate-controlled buildings may persist.