VESTIGIAL WINGS AMONG INSECTS. 1 8/ 



been stopped soon after the trachea began to push out into the 

 wing, and the subsequent changes in the trachea not taking place, 

 it has retained its primitive structure. The persistency of a 

 trachea in this manner with its taenidium in an adult insect wing 

 does not seem to have been previously recorded and is especially 

 interesting in this case as it shows the retention of a distinctly 

 pupal character in the imaginal instar ; i. e., of arrested develop- 

 ment in the wing and not of perfect development on a smaller scale. 



2. Dicczlus splendidns (Coleoptera, Carabidae) (Fig. 16). 



In this form the wings are similar in the two sexes. They are 

 short, slightly over two millimeters in length or one-sixth the 

 body length, and broadly attached to the integument of the 

 metathorax at their bases. The basal articulation is broad and 

 not at all flexible, and as the wings themselves are very strongly 

 chitinized, they remain immovably fixed and cover the postero- 

 lateral angles of the metathorax. The membrane forming the 

 dorsal wall of the first abdominal segment is pushed inward to 

 give space for the wing, which is quite thick. 



Since the other species of this genus, which are winged, make 

 but little use of their wings, it is natural to expect that here both 

 sexes would have the wings reduced to an equal degree, for we 

 are not dealing with a male which flies in search of the female. 

 This points to the idea that it is the difference in the necessary 

 activities of the two sexes that usually causes the male to retain 

 the power of flight longer than the female, and not an inherent 

 morphological or physiological tendency as has been suggested. 



3. Eleodcs sp. (?) (Coleoptera) (Fig. 17). 



One of the common Texan species of this large Tenebrionid 

 genus which was examined has extremely short, often bilobed 

 wings which appear simply as slightly projecting protuberances 

 of the metathoracic wall. Eleodcs tricostata Say and other spe- 

 cies have very similar wings. 



4. ZopJierns sp. (?) (Fig. 1 1 ). 



In this strange Tenebrionid we do not find, as might be ex- 

 pected from the complete coalescence of the elytra, a complete 

 absence of wings. There are structures several millimeters in 

 length, forming thin and delicate flattened sacs which usually 



