548 W. L. TOWER, 



do they have any part in the formation of the adult wing or pigment 

 as in Lepidoptera (Mayer 1896). No "wandering mesoderm" cells 

 enter the wing nor help to form the basement membrane of the hypo- 

 dermis or the middle membrane of the wing. 



The fat body cells have been recorded by Hoffbauer as occur- 

 ring in the wings of beetles, but in those that I have examined they 

 are not common and when these cells have occurred they were simply 

 isolated cells brought into the wing along with the haemolymph in 

 the form of partly transformed "food balls". In Buprestis, however, 

 a considerable mass of these modified fat body cells enters the wing 

 cavity, where they are digested before pupation. 



Nerves. Nerve trunks are found to enter the wing cavity 

 where the nerve break up into small branches, one or more of which 

 enters each vein and penetrates deeper into the wing. These cannot be 

 traced with any certainty by the usual histological methods and I am 

 therefore ignorant of their ultimate distribution. Although sense 

 organs are said to occur in the wings of insects I have not found any 

 structures that could possibly function as such in beetles' wings, and 

 I believe that the nerves end freely between or upon the hypodermal 

 cells and glands. 



8. Homology of the Elytra. 



The homology of the elytra with the wings of other insects is 

 according to some authors doubtful. The divergence of these struc- 

 tures from the typical wing has caused many writers to regard the 

 elytra as homologous to other Hexapod structures. Thus Meinert 

 (1880) regarded elytra as homologous to the tegula of Lepidoptera and 

 Hymenoptera; Hoffbauer (1892) also suggests the same homology. 

 The tegulae are, however, different in structure, and have no venation 

 or tracheation, traces of which were discovered by Kolbe (1886) in 

 the elytra of beetles. Later, Sharp (1896) concluded that the tegulum 

 was a part of the elytron the latter being a true wing. Comstock 

 (1895) adopted Meinert's view ; while Packard (1898) states that after 

 examining a pupal JDoryphora and Clytus he is satisfied that "the 

 elytra are the homologs of the fore wings of insects. Comstock & Need- 

 ham (1899) set aside the early view of the senior author and con- 

 clude that the elytron is a modified fore wing. Finally, Krüger, (1899) 

 after studying Tenebrjo molitor L., Lema asparagi and L. merdigera, 

 concludes that even though the elytra arise exactly like the hind wings 



