. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. 6 THE PERIODICAL CICADA. It SO liappeued that one of the hirgest 17-year broods, together with one of the largest 13-year broods, appeared simultaneously iu the sum- mer of 1868. Such au event, so far as regards these two particular broods, had not taken place since the year 1647, nor will it take place again till the year 2089. There are absolutely no perce[)tible specific differences between the 17-year and the 13-year broods, other than in the time of maturing; but while the insects forming these two classes o
. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. 6 THE PERIODICAL CICADA. It SO liappeued that one of the hirgest 17-year broods, together with one of the largest 13-year broods, appeared simultaneously iu the sum- mer of 1868. Such au event, so far as regards these two particular broods, had not taken place since the year 1647, nor will it take place again till the year 2089. There are absolutely no perce[)tible specific differences between the 17-year and the 13-year broods, other than in the time of maturing; but while the insects forming these two classes of broods are not specifically distinct, they are good and distinct races which do not cross, and I have therefore, for convenience sake, named the 13-year broods Cicada tredeeim. TWO DISTINCT FORMS. It is not a little singular, also, that two distinct forms occur in both races—a large one and a small one—the former by far more numerous than the latter. This fact has been observed in past years, and was. 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 United States. Bureau of Entomology. Washington : G. P. O.
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