f 





MEMOIRS 



OF THE 



American Museum of Natural History 



VI.— MONOGRAPH OF THE SESIID/E OF AMERICA, 



NORTH OF MEXICO. 



By William Beutenmuller. 



Plates XXIX-XXXVI. 



Introduction. 



The Clear-winged Moths, or Sesiidae, may be superficially recognized by their 

 narrow and more or less transparent wings, by the clavate or filiform antennae, 

 which are either ciliate, pectinate, or simple ; also by the tuft at the end of the body, 

 which they can spread like a fan, especially in the male. At first sight, a box of 

 these insects would appear to be a number of individuals differing only in size, 

 with here and there a slight change in the coloration. On the whole, the specific 

 and generic differences are very slight, though constant in most cases, but it re- 

 quires close observation and careful comparison of specimens to distinguish one 

 from another. In some species, especially of the genus Sanninoidea and group Pyr- 

 rhotcenia, the males differ from the females, and in a number of instances the males 

 have been described under one name and the females of the same species under 

 another, or individuals more or less worn through age and flight have been 

 described and named as different species, thus creating considerable confusion in 

 the study of this family of moths. Another difficulty surrounding this family is 

 that the larvae feed within the stems of plants, in roots, or under the bark of 

 trees, and thus are not easy of access, while the work of raising them through 

 their various stages becomes a task of no inconsiderable difficulty ; moreover, 



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