. Bulletin. Natural history; Natural history. 138 Illinois Natikal History Si kvey Bulletin- the distribution of any given species of aphid over Xorth America or the world as a whole. The aphid, Euccraphis bctulac (KochJ. naturally oc- curs in Illinois only where the canoe or paper birch () is native, but its physiological construction is such that it can live on specimen trees in various parts of the state. It would be a mistake to think of the present natural distribution of this plant louse as we find it in Illinois as being strictly in conformity with certain optima of temperatures,
. Bulletin. Natural history; Natural history. 138 Illinois Natikal History Si kvey Bulletin- the distribution of any given species of aphid over Xorth America or the world as a whole. The aphid, Euccraphis bctulac (KochJ. naturally oc- curs in Illinois only where the canoe or paper birch () is native, but its physiological construction is such that it can live on specimen trees in various parts of the state. It would be a mistake to think of the present natural distribution of this plant louse as we find it in Illinois as being strictly in conformity with certain optima of temperatures, humidities, and other meteorological factors. The maximum extent of its distribution certainly can be limited or influenced bj- such Pig. 14. (Left) Distribution of Aphis iioini DeGeer and one of its many hosts, the cultivated apple, Ppnis Mains. Fig. I'i. (R\(ihl) Distribution of Macrosiphiiiii pisi (Kaltenbach) and one of its hosts, the red clover, TrifaUuDi pinlciisc. but these limits cannot be determined solely by a glance at a distri- bution map of this aphid as we see it in Illinois where the natural range of its host is alone stifificient to be the decisive and the limiting factor. There are, no doubt, species of plant lice in Illinois wliich, in spite of having a suitable or combination of hosts in all j'arts of the state, exhibit a tendency of ".southerness" or "northerness" of distribution because of limiting factors of a physiological nature. Oiu" survey of the plant lice fauna, however, has not been thorough Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Illinois. Natural History Survey Division. Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
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