J24: PEKIODICAL CICADA. 



This species appears to belong to the sub-genus Exorista, of Meigen, closely allied to Ta- 

 china proper, and differing from it chiefly in having the eyes hairy, and in the presence of 

 bristles on the middle of the second and third abdominal segments, as well as at their poste- 

 rior margins, whilst Tachina has only the latter. 



The following table exhibits the distinctive characters of the three closely allied sub-genera, 

 Tachina, Exorista and Lydella: 



Third joint of the antennae about twice as long as the second. Face nearly vertical, 

 with few or no bristles at the sides. 



Eyes naked. Stout bristles at the hind margin only of the second and third 



abdominal segments Tachina. 



Eyes hairy. Stout bristles on the hind margin and middle of the abdomi- 

 nal segments Exorista . 



Third joint of the antennae three times as long as the second. Face oblique, bristled 

 at the sides. Eyes generally hairy. Usually two bristles on the middle of the 

 second and third abdominal segments Lydella . 



PERIODICAL CICADA. 



( Cicada Septendecim. Linn. ) 



Order of HOMOPTERA. Family of Cicadid^. 



Harris' Treatise, page 206; Fitch's First Report, page 38; Riley's First Report, page 18. 



The year 1871 has witnessed one of the periodical returns in North- 

 ern Illinois and the borders of the contiguous States, of this notorious in- 

 sect more cocnnaonly known by the name of the Seventeen-year Locust. 



In several respects this is one of the most remarkable and anomalous 

 of the insect tribes. Its unprecedented longevity in its larval state 

 and subterranean abode, the regular periodicity of its appearance, and 

 the elaborate and systematic deposition of its eggs in the twigs of 

 trees often near the summit of forest trees, whilst the young hatched 

 from them live exclusively in the earth, are all ca culated to attach a 

 peculiar interest to the history of the Cicada. 



The history and habits of this insect after it has emerged from the 

 earth and assumed its winged form, have been pretty thoroughly traced 

 by the authors enumerated at the head of this article, and by many 

 other observers. To those authors the reader is referred for a detailed 

 account of this insect. "We shall, in the present article, contine our- 

 selves chiefly to a record of the observations made during the season, 

 and especially to such facts as bear upon unsettled points in its history. 



GEOGRAPHICAL EANGE. 



Amongst the many remarkable circumstances in the history of the 

 Periodical Cicada, is the great extent of country in which they have 



