2o8 CALIFORNIA ACADEMY OF SCIENCES. [PROC. 3D Ser. 



larvae from beginning to complete condition, and to ascertain 

 that the correspondence between the greatly modified parts 

 of the adult mouth, adapted for lacerating and lapping or 

 sucking, and the generalized biting parts of the larva can 

 be satisfactorily established, mandible for mandible, maxilla 

 for maxilla, and labium for labium. In the larval mouth the 

 homologies of the parts with the parts in the biting orthop- 

 terous mouth are apparent. They can be traced, of course, 

 in their embryonic development from budding appendages 

 to completed larval mouth-parts, leaving no possible doubt 

 of their homologies; and this has been done for Simuliuni 

 by Metschnikoff. As the eggs of the Blepharoceridse are 

 as yet unknown, this embryonic tracing cannot 3^et be done. 



Imaginal Eyes (PL XXII, fig. i). With regard to the 

 curious condition of the eyes of the adult Blepharocerids, 

 the following is taken from the account in the Entomological 

 News (Kellogg, 1900) of the eyes of Blepharocera ca-pitata. 



The other specially interesting point in the imaginal 

 anatomy of Blepharocera is the structural condition of the 

 compound eyes. It has long been observed that several 

 flies {Simulium, Tabanus^ et al.) and certain other insects 

 (Libellulidas, Ascalafhus, Ephemeridge, et al.) have two 

 sizes of facets in each compound eye; that some have the 

 field containing these differently sized facets well delimited, 

 the fields being in some cases actually separated from each 

 other by a non-facetted line or by a constriction. When 

 this constriction is so complete that the eye is truly divided, 

 it may fairly be said that there are two pairs of compound 

 eyes, the two eyes of each lateral pair differing in the size 

 of the facets. This last extreme condition exists in the case 

 of the males of certain Ephemeridse and in both males and 

 females of Blepharocera capitata. [And in almost all other 

 Blepharocerid species. See PI. XVIII, all figures.] 



The eyes of Blepharocera are plainly divided; or it may 

 be said that there are two on each side (PI. XVIII, figs. 

 I and 2). One of these eyes is dark colored, has small 

 facets, and faces anteriorly and laterally. It is fairly 



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