152 AMERICAN COLEOPTERA. 



Scarites sitbterranens. Tachys xanthopns. 



Clivina bipimtulata. Pterostichus sayi. 



" ferrea. Dynastes tityns. 



Aspidoglo.isa subangidata. Anomala undulata. 



Panagieus fasciatus. Alindria teres. 



The New Mexico list contains over 135 such species, indicating 

 that the eastern fauna is really crossing the plains to some extent, 

 and not only reaching us by way of the northern mountains. There 

 are strong reasons for believing that a considerable part of this 

 migration is recent, and has been assisted involuntarily by man. 

 This affords, of course, a strong argument in favor of the speedy 

 exploration of western regions, in order that their original fauna 

 may be ascertained before it is unduly contaminated by introduced 

 forms. Fortunately for the naturalist, the dessert will not quickly 

 or easily accomodate alien elements,* but it is quite otherwise in 

 more ordinary localities; and as Perkins has shown in the Hawaiian 

 Islands the result may be destruction as well as confusion. 



The number of species common to New Mexico and Southern 

 California, but not known from Colorado, is over 160, indicating 

 a wide-spread southwestern fauna ; but in general, the species of 

 the Southern California coast region are not those of the Rocky 

 Mountains. 



We find over 30 names of New Mexico species listed from the 

 Lower Rio Grande, but not in the Colorado, Southern California or 

 District of Columbia lists. Such are for example: 



Cicindela circiimpicta. Oodes cuprxeus. 



" severa. Iscliiodontus ferreus. 



Dyschirius terminalis. Ludius texanus. 



Philophuga viridicollis. Agrilus addendus. 



Hellnomorpha ferruginea. Mastinocerus texanus. 



The following are examples of characteristic southern genera 

 which reach New Mexico, but do not enter Colorado : 



Thalpius. Thrincopyge. Aphoriides. Derobrachus. 



Hololepfa. Lycus. Strntegus. Tylosis. 



Sandalus. Plusiotis. Allorhina. Dendrobias. 



* Unless brought from similar regions. A few years ago some date palms 

 arrived in Washington with about fifty species of the Algerian fauna from snails 

 and slugs to mites, centipedes and coccids. Of course they were suitably treated 

 for the destruction of all these, before being sent to our southwestern country ; 

 but a careless importer could have provided us with quite a fauna in this single 

 sending! One species of Coc.cidse did get through alive. 



