14 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



area of overlap coincides very closely with 

 the Corn Belt. Another type of range in 

 this class is illustrated by Hydropsyche 

 aerata, which appears to have a very re- 

 stricted range, fig. 15. Among the Hydrop- 

 tilidae are several species which, on the 

 basis of present records, appear to be re- 

 stricted to the Corn Belt and its immediate 

 vicinity; these include Hydroptila angusta, 

 grandiosa and ajax and N eotrichia falca. 



Ranges Projecting Into Illinois 



Northern-Northeastern Species. — Of 



the caddis flies having a range that just 

 touches Illinois, or nearly touches this state, 

 the most numerous are northern and north- 

 eastern species. Examples include repre- 

 sentatives of many families: Hydropsyche 

 slossonae and recurvata, fig. 16, Chimarra 

 aterrima, fig. 17, Oecetis osteni, Limnephilus 

 moestus, rhombicus and argenteus, and many 

 others. These include both lake and stream 

 species. Each of these species has a slightly 

 different range, some extending south just 

 into Illinois, others deeper into the state 

 and still others not reaching it at all. A 

 number of these species, such as Alystacides 

 longicornis and Neureclipsis bimaculatus, 

 are Holarctic and many more will undoubt- 

 edly prove to range extensively northwest- 

 ward through the northern coniferous for- 



est. This group, as would be expected, em- 

 braces a large number of species which have 

 been found in Illinois in isolated and local 

 colonies and an additional number which 

 have been taken in southern Wisconsin and 

 Michigan but not yet in Illinois. 



Northeastern-Ozark Species. — One of 

 the most surprising discoveries in this in- 

 vestigation was the unexpected number of 

 species common to both the northeastern 

 states and the Ozark series of mountains, 

 including various areas in Oklahoma and, 

 to some extent, the "cross-timbers" which 

 extend diagonally across Texas. Most of 

 the species exhibiting this type of range 

 occur in Illinois, especially along its north- 

 ern, eastern and southern margins. Present 

 collections indicate that the Illinois Ozarks 

 are one of the few existing connecting links 

 between the northeastern and southwestern 

 parts of the range. This is \vell shown in 

 the case of Chimarra obscura, fig. 18. 



Some species, such as Cheumatopsyche 

 sordida, have a range of the same type but 

 highly discontinuous, so that the Ozark 

 records are at a great distance from any 

 others known at present. 



Ozark Species. — A few caddis flies occur 

 only in the Ozarks, extending throughout 

 their course from Illinois to Oklahoma and 

 into the neighboring hills and ranges. Ex- 

 amples include Agapetus illini, Dolophilus 



Fig. 16. — Range map of Hydropsyche 

 slossonae and recurvata. 



Fig. 17. 



feria. 



-Range map of Chimarra aterrima and 



