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inois Natural History Survey Circular 49 



occur in Illinois only in the Dunesland region. Several Arctic sand- 

 pipers, for example the purple sandpiper, and some of the northern 

 terns nest far north of Illinois but spend the winter in the Zion region. 

 Many insect species that are chiefly northern still occur in the 

 northeastern corner of Illinois. Perhaps the best known of these are 

 the many species of sawflies, plant bugs, and moths that feed only on 

 native tamarack and have been collected in Illinois only in the bogs 

 at Volo and other bog areas in Lake County. Insect denizens of the 

 Dunesland include many other examples of northern species not found 

 in the bogs. These include a leafhopper and an aphid that live only 

 on bearberry, figs. 12 and 13, another leafhopper and another aphid 



Fig. 13. — Bearberry fwigs infested with the bearberry aphid, Tamalia coweni. The aphids 

 feed on the terminal leaves; their feeding causes the leaves to curl and swell and to form bean- 

 shaped galls. Several galls are shown at the ends of twigs (one gall indicated by arrow). When 

 fully developed, the galls are bright red and contrast sharply with the bright green of the normal 

 bearberry leaves. 



