205 



that it was a case of many kcvs to open one Idck ; l)ut after 

 an extensive stndy, along with I)i'. l)a\i(l Shar]), of these 

 organs in Coleoptra, and their function during copuhition, [ 

 was forced to change my opinion, for the evi(h'nce sliows that 

 in numy cases the key fits its hx*k, and its <iwn lock oidy. 

 In these cases the coadaptation is hetwetMi the memhranous 

 internal sac and its armature and the memlti-aiidus uterus. 

 In the Derbidae I have observed a c(ia<hi])tati(>ii between the 

 genital styles and anal segnnent and certain knobs and <h'- 

 pressions on the female, a coadaptation I did not suspect until 

 I observed the sexes in copula. How far some of the uiiuo)' 

 changes (i. e. N. I'oae. N. I'oae-phyUodii and oahueiisis) would 

 prevent fertilization it is impossible to say at present, but that 

 such structures as the aedeagi of N. hoae, N. jicrlrnisi. A. 

 raillardiae. N. ipomoeicoJa, N. halia. N. sltarpi and .V. (/if- 

 fardi could all perform the same mechanical opcu-atiou in a 

 similar numner is highly improbable. On the other hau<l, 

 to account for these structures along with a coada])tatiou in 

 the female by J^atnral Selection is to me unthinkable; the 

 more one tries to follow out in thought such an operation the 

 greater the difficulty becomes. 



Isolation. Our collections are not complete enough for us 

 to judge of the full effect of isolation on species formation, 

 but enough is known to demonstrate that isolation and species 

 formation coincide to a very large extent. A few" species are 

 dispersed over two or more islands, others over one island, 

 but a large number have very limited habitats. D. iiin(d>dis 

 is a good example of this limited range, it being found only 

 on a small ridge a few feet wide and not more than a quarter 

 of a mile long.* According to our present collections Oahu 

 has 42 species, Hawaii 20, Kauai 12, Maui 11, ]\rolokai 7 

 and Lanai 5. This does not represent the richness of, but 

 only the amount of collecting done in each island. 



In spite of this it is possible that a study of the distribu- 

 tion of these insects in the Archipelago may lead to some in- 

 teresting results, if it be borne in mind that more extensive 

 collecting is likely to modify the present conclusions. That 

 more species will be found in the Island of Hawaii, when the 



*Mr. Timberlake has since found it on the Lanihuli ridge, on the 

 western side of Nuuanu Valley, and Mount Kaala of the Waianae 

 Range. — Ed. 



