August, 1944 



Ross: Caddis Flies of Illinois 



15 



Fig. 18. — Range map of Chimarra obsciira. 



shawnee and Ochrotrichia anisca. These 

 species and others of similar faunistic habits 

 occur in the Ozark Hills of southern Illi- 

 nois. 



Southwestern Species. — Another group 

 of Illinois caddis flies is southern or south- 

 western in general distribution. This in- 

 cludes such forms as Cheumatopsyche lasia, 

 fig. 12, and Chimarra feria, fig. 17. The 

 range of each centers around Oklahoma, 

 with extensions eastward to Illinois and as 

 far northward as Montana or Minnesota. 

 It is interesting to note that the former ex- 

 tends throughout the northern portion of 

 Illinois; the latter has been found in Illinois 

 only in the Ozark Hills of the southern part 

 of the state. 



Certain other southern or southwestern 

 species have a range extending into southern 

 Mexico. This is true especially of many 



Hydroptilidae, of which Mayatrichia ayama 

 ranges from southern Mexico to New York, 

 following closely the pattern of Chimarra 

 obscura in fig. 18. 



Southeastern Species. — A few members 

 of the Illinois fauna have been collected 

 in other states only to the south and east. 

 This group includes Hydropsyche incom- 

 TJioda, Cheumatopsyche burksi and Hydro- 

 psychid Genus A, extending from Illinois to 

 Georgia or Florida. A small number of 

 species not yet taken in Illinois are known 

 to range from Georgia to Indiana; these 

 include Macronemum transversum and Hy- 

 dropsyche depravata, which have essentially 

 the same range as the three just mentioned. 

 Hydropsyche phalerata has a range which 

 centers in the southeast but differs from 

 the above examples by extending consider- 

 ably north of Illinois, fig. 15. 



Summary 



A review of the above data shows that 

 in North America the caddis flies form sev- 

 eral fairly distinct geographic groups. One 

 of these, embracing the states of the Corn 

 Belt, centers roughly in Illinois. Through- 

 out the northern and northeastern states is 

 one large group of species ; to the southwest, 

 extending through the Ozarks into Mexico, 

 is a second large group ; and to the south- 

 east is a third smaller group. All three of 

 these contain fairly distinctive species that 

 range into Illinois, which is approximately 

 at the meeting point of these "avenues" of 

 distribution. This axial position has been 

 demonstrated with several other groups of 

 insects studied for the state, including the 

 Miridae, Orthoptera and Plecoptera, al- 

 though in each the details are different. 



COLLECTING AND PRESERVING 



Caddis flies have such diverse habits and 

 habitat preferences that several kinds of 

 collecting are necessary to get representa- 

 tive samples from a given area. In most 

 cases these same methods are equally effec- 

 tive with other aquatic groups, including 

 stoneflies, mayflies and midges. The adults 

 are aerial and the larvae aquatic; further, 

 it is more the rule than the exception that 

 at any one place the adults in the air and the 

 larvae in the stream belong to different sets 

 of species. Collecting for one phase must 

 not be stressed to the exclusion of the other. 



With one exception, caddis flies, both 

 immature stages and adults, should be col- 

 lected in liquid, preferably 80 per cent grain 

 alcohol. The exception is adults of the 

 genus Leptocella, readily distinguished in 

 the field by a long, narrow shape, extremely 

 long antennae and white ground color (see 

 p. 213). In this genus it is necessary for 

 specific diagnosis to use color patterns 

 formed by the delicate wing hairs, which 

 rub off with remarkable ease. Specimens of 

 this genus should be killed in a cyanide or 

 other dry bottle, a few at a time, and care- 



