. The distribution of periodical cicadas in Illinois. Periodical cicada. 11 Main Street, Rockford, indicating the survival of this brood, despite low numbers, over the past 136 or so years of human occupancy of that city. In a woods at Castle Rock, Ogle County, the eastern portion contained no cicadas, whereas the western portion, having the same terrain but possibly less sand in the soil, contained a good singing popula- tion. There I found adults, skins, and holes in the ground. This observation and others bear out the contention that each woods is not necessarily uni- formly inhabited. FUTU
. The distribution of periodical cicadas in Illinois. Periodical cicada. 11 Main Street, Rockford, indicating the survival of this brood, despite low numbers, over the past 136 or so years of human occupancy of that city. In a woods at Castle Rock, Ogle County, the eastern portion contained no cicadas, whereas the western portion, having the same terrain but possibly less sand in the soil, contained a good singing popula- tion. There I found adults, skins, and holes in the ground. This observation and others bear out the contention that each woods is not necessarily uni- formly inhabited. FUTURE EMERGENCES OF PERIODICAL CICADAS IN ILLINOIS Future twentieth-century emergences of periodical cicadas in Illinois are shown in Table 2. Table 2. — Future twentieth-century emergences of piriodical cicadas in Illinois. Year of Emergence Brood Cycle in Years 1976 Lower Mississippi River Valley Brood (Marlatfs XXIII i 1980 lowan Brood (Marlatfs III) 1985 Great Southern Brood (Marlatfs XIX) 1987 Great Eastern Brood (Marlatfs X) 1989 Lower Mississippi River Valley Brood (Marlatfs XXIIK 1990 Northern Illinois Brood (Marlatfs XIII) 1997 lowan Brood (Marlatfs III) 1998 Great Southern Brood (Marlatfs XIX) DISCUSSION A composite map of the distribution of the Illinois broods of periodical cicadas is shown in Fig. 5. The borders of the range of each brood are only approxi- mate except in a few regions, as critical areas and woods which should have been put under close sur- veillance for more precise information could not be recognized until after two or three emergences had been surveyed. In general, the distributions of these broods fit nicely with the distributional patterns of other organisms viewed in relation to geological events. Most of the region occupied by the Northern Illinois Brood lies within the Wisconsin glacial plain. The lowan Brood, except for the region inhabited by the disjunct population in De Witt, Piatt, and Champaign counties, occupies a western spur on erode
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Keywords: ., bookcentury1900, bookpublisherurban, booksubjectperiodicalcicada
