l82 



FAUNA HAWAIIENSIS 



small vestigial wings ; but specimens occur in which the vestiges are larger, though 

 functionless, and also other individuals in which the wings are of full size and functionally 

 fit ; the discontinuity of the variation being in this case very remarkable. 



It will thus be seen that my observations, admittedly of a very imperfect character, 

 tend to show that probably the phenomena of wing-variation are different in each of the 

 three groups that make up the Carabidous fauna of Hawaii. 



Chaetotaxy. This subject has become of an importance that is still increasing in 

 several orders of Insects. From the chitinous skeleton there stand out hairs that in 

 some cases penetrate the chitin and are connected with a special nerve, thus forming a 

 simple but effective set of sense-organs. The description of the ways in which these 

 hairs are arranged is called chaetota.xy. In Carabidae those on the head have been 

 found to be of great importance for classification. The great sub-family Harpalini — 

 possessing probably 100,000 species — is characterised by the possession of two intra- 

 orbital setae on each side. All our Hawaiian Carabidae belong to this sub-family. 



The setae on the thorax I consider to be also of considerable importance in the 

 three groups to which the Hawaiian Carabidae belong. Their number is, normally, two 

 on each side, one at or near the hind angle, the other a little before the middle. This 

 condition is varied by the absence of one or of both of the setae in certain genera or 

 subgenera'. Outside the Hawaiian islands this normal condition of a pair of thoracic 

 setae on each side seems to be extremely usual in the two groups Anchomenides and 

 Bembidiides, and it is the condition existing in the only extra- Hawaiian genus — Cyclo- 

 f/iorax— that is allied to the Hawaiian Pterostichides. Just as we found the Hawaiian 

 Carabidae to be remarkably subject to degeneration of the wings, so do we find them to 

 be remarkable for the diminished number or total absence of these thoracic setae. The 

 cephalic setae remain constant in their number in Hawaii, but of the 208 species no less 

 than 146 have a diminished number of setae, as shown in the following Table of the 

 thoracic setae of Hawaiian Carabidae. 



Systematists are not yet agreed as to the taxonomic value of these thoracic setae. In some divisions of 

 Carabidae they are but of little importance ; but in the three groups with which we are occupied I am con- 

 vinced that they are of generic value. There are also a few cases that detract from the importance of the 

 intra-orbital setae. 



