Our Livint; Resources — /nveilehrnles 



IS5 



In Illinois, stonetlies (Insecta: Plecoptera) 

 were collected extensively from 1926 through 

 1940 by T.H. Prison (Prison 1929. 1935. 193^7. 

 1942). with additional winter-emerging stone- 

 flies collected from I960 to 1970 by H.H. 

 Ross's "Winter Stonetly Club"' (Ricker and 

 Ross 1968, 1969: Ross and Ricker 1971 ). From 

 the thousands of specimens collected, the 

 Illinois Natural History Survey has an excep- 

 tional record of species diversity and spatial dis- 

 tribution of Illinois stonetlies. 



In 1990 we began a reevaluation of the 

 species richness and spatial distribution of 

 Illinois stonetlies (Webb and Harris 1993). The 

 focus of this study was to compare current 

 species richness and distribution patterns with 

 those determined by Prison, Ross, and Ricker. 

 To do this, we developed a data base for the 

 Illinois specimens in the collections of the 

 Illinois Natural History Survey, and we exten- 

 sively resurveyed stonetlies in each of the 23 

 major drainages within the state (Pigure). 



Status 



We evaluated the status of each stonetly 

 species on the basis of the locality information 

 and classified each species as rare, uncommon, 

 or common (Table). This evaluation revealed 

 that 39% of the 6 1 species reported were known 



Figure. Twenty-tive major river drainages in Illinois. 



from three localities or fewer. In addition, we 

 developed a checklist of the Illinois species and 

 updated their varied nomenclature. 



After 4 years of collecting we consider 1 3 

 Illinois stonetly species rare (Acwueiiha filicis 

 Prison; A. perplexa Prison; AUocapniu nivicola 

 [Fitch]; A. smithi Ross and Ricker; HaploperUi 

 brevis [Banks]; Isoperla hiirksi Prison; 

 Nemoiira trispinosa Claassen; Piimgnetiua 

 media [Walker]; Prosioia completa [Walker[; 

 Shipsu rotiiiula [Claassen]; Soyciiiini vallictdar- 

 ici [Wu]; Zealeiictra fra.xina Ricker and Ross; 

 and Z. nciifl Ricker and Ross). We found that 6 

 have been extirpated from Illinois {AUocapiua 

 illiuoensis Prison; Alloperki roherti Surdick; 

 Amphinemura nigritta [Provancher]; Isoperla 

 conspicua Prison; /. marlynia [Needham and 

 Claassen]; Leiictra tenuis [Pictet]); 4 species 

 have possibly been extirpated (Isogenoides var- 

 ians [Walsh]; Leiictra sihleyi Claassen; 

 Nemocapnia Carolina Banks; Paracapnia angii- 

 lata Hanson), and 1 rare species (Alloperki 

 caudata Prison) is common. One species. 

 Soyedina vallicidaria [Wu], has been added to 

 the state list. 



Data from over 50.000 Illinois stonetly spec- 

 imens in the collections of the Illinois Natural 

 History Survey are being analyzed to determine 

 the species richness and spatial distribution of 

 Illinois stonetlies by drainage basin. This assess- 

 ment will be based separately on earlier data 

 (Prison 1929. 1935. 1937, 1942; Ricker and 

 Ross 1968. 1969; Ross and Ricker 1971) and 

 will evaluate these data relative to collections 

 since 1990. 



Apparent Trends 



In reevaluating the current status of Illinois 

 stonetlies. our first concern was the status of so 

 many "rare" species in Illinois. We wanted to 

 determine if the limited locality records for 

 these species reflect actual rare distribution in 

 Illinois, inadequate sampling, or an accidental 

 occurrence (i.e., the species is not normally a 

 part of the indigenous Illinois fauna). It is now 

 apparent that 1 3 of these species are truly rare in 

 Illinois; many of these are at the edge of their 

 distributions. The eastern deciduous forest with 

 its gravel- and cobble-bottomed streams 

 extends only slightly into Illinois and several of 

 these rare species are found only in these habi- 

 tats. Similarly, the limestone and sandstone 

 outcroppings of the Shawnee Hills in southern 

 Illinois offer another area of high-quality 

 streams and are home for several rare species of 

 Illinois stonetlies. To a very limited extent, 

 springs in Illinois are a refugia for a few rare 

 species. For only one species. Alloperki cauda- 

 ta. does it appear that inadequate sampling dur- 

 ing April and May produced a biased picture of 



Plemiuircys pictetii, one of ttie 

 largest stonetlies in Illinois, is 

 common to big rivers. In the 

 nymphal stage, this species serves 

 as an imponant food for fish. 



