234 



NEW YORK STATE MTSEUM 



were also observed at the Rural ceinetrry near Albany and at liath-on- 

 Hudson. These peculiar structures are made by the nymphs brinjj^ins^ up 

 pellets of earth and depositin*^ them about the mouths of their o^alleries. 

 Mr Lander observed one repairing- its injured chamber. There have been 

 a number of theories advanced to account for these peculiar structures, 

 but as they were built under such very diverse conditions, no explanation 

 ajjpears to be entirely satisfactory. 



II;;. 4? jNh.p blunviiig tlic ilistribuiion of the broods of the 17 year race. (After Marlatt, V. X 

 Dcp't Agric. Div. Ent. Bui. 14, n. s. i8<)8. p. 26) 



Description. Tlu- perfect insect may be easily recoi^nized Ijy its black 

 bod\- and the brit^ht red (tyes, ami the red \eined wiuijs, in connection with 

 plate 11, fis^nire 17. .\ smaller variet), described by Dr I'"isher as 

 T ibicen cassinii, occurs in I'onncclion with the lar_<j;e form. 



Distribution. The j.(';neral distrilnition of the i 7 year broods is (graphi- 

 cally re|)resentt-d in the accom|)anyin!^ map prepared by Dr C. L. Marlatt. 

 It will be seen, in connection with the one showint; the distribution of the- 

 broods of the 13 year race, that these latter overhi]) those havins^^ a lon;^er 

 developmental period only to a limited extent. 



