238 THE UNIVERSITY SCIENCE BULLETIN. 



STRUCTURAL ADAPTATIONS TO FEEDING. 



External. 



The Corixids possess the most obvious adaptations of their 

 limbs to definite functions of any of the v^ater bugs. As 

 early as 1833 Leon Dufour, in his "Recherches anatomiques et 

 Physiologiques sur Les Hemipteres accompagnees de consid- 

 erations relatives a I'histoire naturelle et a la classification 

 de ces insectes," gave a detailed description of the various 

 limbs of Corixids. In 1873 Buchanan White, to v^^hom we owe 

 a great deal for a splendid series of notes regarding Corixids, 

 mentioned the function of the different parts, based upon 

 his personl observation. He states that the hind limbs are 

 flattened and fringed for swimming, that the long, slender 

 middle limbs anchor the bug to some submerged object, and 

 the fore limbs are employed in food getting, though he con- 

 fessed his uncertainty as to the forage gathered. 



Comstock, in his "Introduction to the Study of Entomology," 

 also notes the differentiation of the limbs. 



The very unique mouth parts that led Borner, 1904, to 

 place them in a suborder by themselves, and for which he 

 proposed the name Sandalioi^^liyncJia, are well adapted to 

 the unusual method of feeding practiced by these insects. 

 There is no extended beak as in other bugs, yet a morpho- 

 logical study of the various parts, such as those made by 

 Metschniikoff, 1866, Giese, 1883, Wedde, 1885, Heymons, 1899, 

 Bugnion and Popoff, Muir and Kershaw, and others indicate 

 the close relationship of these with other bugs. The draw- 

 ings on plate XXX show the mouth parts. The face of the 

 bug is seen to be flat with the buccal opening on the front 

 side rather than at the tip. Two triangular flaps, controlled 

 by muscles, permit the enlargement of the orifice. The sty- 

 lets are very short and stout, the outer pair blunt-tipped and 

 notched on their outer margins. A condition quite different 

 from the pointed and retrorsely-barbed stylets of Notonecta, 

 for instance. The inner pair are broad, placed one above 

 the other, and rolled into semi-cylinders. Bugnion and Popoff 

 say of these internal stylets of Hemiptera: ". . . The 

 internal stylets forming by their juxtaposition two conduits, 

 very fine, one of which ordinarily placed on the dorsal side is 

 the "Canal de succion" which is continuous from beak to 



