2 68 TEE POPULAR SCIENCE MONTHLY 



and mountain. This results in her showing the characteristics of an 

 island fauna and flora, with their numerous monotypic plants and ani- 

 mals, unique, solitary kinds, developed in isolation and under special 

 local conditions. California's insect fauna, therefore, includes many 

 unique species and genera, and even a few families, not found else- 

 where on this continent, not even in other neighboring states. This 

 makes it an exceptionally happy hunting-ground for the insect-collector 

 and systematist. 



But not only does its biological isolation give an exceptional interest 

 to its insect kinds, but its extraordinary topographic and climatic diver- 

 sity introduces unusual and highly contrasted conditions in insect living 

 and, through environmental influence, produces strange kinds of special- 

 ization of structure and habit. For example, the brave little butterflies 

 (Chionohas) that live on the summits of the Sierra Nevada are bound 

 to attract our attention, for their nearest cousins (other species of the 

 same genus) are similar butterflies confined to the summits of the 

 Eocky Mountains, 1,000 miles away, and Mt. Washington in New Hamp- 

 shire and Mt. Katahdin in Maine, 2,000 miles farther. These lonely 

 mountain-top butterfly kinds are good illustrations of the fact that alti- 

 tude can replace latitude in distribution. And they undoubtedly owe 

 their marooning on widely separated peaks to their neglect to follow the 

 retreating glaciers of the close of the Great Ice time northward, re- 

 maining, instead, in these isolated alpine regions where conditions have 

 remained practically glacial. 



The California mountains, especially the Coast Eange, have another 

 especially interesting group of insect inhabitants in a curious small fam- 

 ily of delicate, long-legged, stream-haunting flies called net-winged 

 midges (Blypharoceridse). Although scattered widely over the world in 

 mountain regions, hardly more than a score of species are known, of 

 which almost one half are peculiar to the Pacific coast. Their imma- 

 ture life is passed, as larva and pupa, in the swiftest and clearest of 

 mountain streams, clinging by strong little sucking pads to the smooth 

 rock bottom on the verge of a fall. The larvae die if they happen into 

 slow or stagnant water, and many of the delicate flies are torn away by 

 the current and lost as they emerge from the pupae. But, neverthe- 

 less, with all this restriction of life to certain narrow and dangerous 

 conditions, the net-winged midges, like the water ouzels, near whom 

 they domicile, maintain a successful existence to add to our interest in 

 the mountain streams. 



Another interesting group of insects, well represented in California 

 and very sparingly elsewhere in this country or anywhere out of the 

 tropics, is the family of termites, or white ants (Termitidse). Indeed, 

 out of the seven species known to occur in the United States, but one 

 is found in the east, the other six being limited to the southwest and 



