( clxv ) 



sternite. The sedceagus is common to all insects, and is 

 exceedingly varied in its states of development. The clasping 

 organs do not obtain in all orders, as has been already shown. 

 In the Odonata the external organs have developed along 

 entirely different lines, owing no doubt to their quite different 

 economy, but on the second segment of the abdomen there 

 are organs for grasping the ovipositor of the female, and 

 these may be in process of further development ; this line 

 of study, already begun by some American morphologists, 

 will, I hope, be deeply probed into. The old and vast 

 order of Coleoptera present a field of research of the very 

 utmost importance and of the utmost interest. I believe it 

 is probable that clasping organs, as understood by Lepi- 

 dopterists, Trichopterists and Dipterists scarcely exist. 

 There are large external sclerites in certain groups, for in- 

 stance in the Telephoridae, in some of the weevils such as the 

 genera Psalidtira and Ichthyurus, as already referred to, but 

 I am very doubtful if they are homologous with the complex 

 external organs of other orders. In the Hymenoptera also 

 comparatively little has been done in this line of study, in 

 spite of the fact that beautiful and highly complicated struc- 

 tures are common, and that the aculeate section has the 

 additional interest of being provided with a sting emitted 

 from the telum. The European war has prevented me from 

 getting specimens of several of the less popular and of the 

 lower orders that I had quite expected to be able to figure, 

 but as regards the Trichoptera, the Lepidoptera and the 

 Diptera, it is evident that the external modifications of the 

 ninth and tenth abdominal segments are very ancient, and 

 that they have persisted quite as strongly where apparently 

 there was no special need for their persistence — I refer, of 

 course, to those species of Lepidoptera with so-called sub- 

 apterous females. It appears to me to be almost certain 

 that these organs are modifications of the ninth and tenth 

 abdominal segments, the Micropterygidae and the Trichoptera 

 (in many cases) seem to prove this in the formation of the hind 

 section of these organs, that section being an almost complete 

 ring, like the other abdominal segments, only being (to-day) 

 without the division between the tergite and sternite, and I 



