23,6 Schultze: Pachyrrhynchus 611 



well as species were developed. It is assumed that by an adap- 

 tation in conformity to special surroundings and environment 

 their peculiar features of development were brought about; 

 geographic and climatic factors have undoubtedly played the 

 most important parts in bringing about such extraordinary de- 

 velopments. In the pachyrrhynchids the soft wings are absent 

 and the elytra are firmly united at the suture. These characters 

 may have been brought about as the direct results of geologic 

 changes at comparatively very ancient times, due to isolation 

 or island formation. Analogous conditions and similar results 

 are found in the insect fauna of other island regions. 3 



I assume that during a very early period, at a time when the 

 land masses which now form the Malay Archipelago were 

 still connected with each other but already disconnected from 

 Formosa, one or probably several ancestral forms of the pachy- 

 rrhynchids were distributed over the regions comprising the Phil- 

 ippines, possibly the Moluccas, and the regions around New 

 Guinea. At a later period, and after the land masses had been 

 transformed into islands, the power of flight in these beetles 

 became of secondary importance, or it may have been a direct 

 handicap on account of peculiar physical conditions, such 

 as torrential rains together with heavy winds and storms in 

 these regions. As the result of a combination of such factors 

 wingless forms slowly developed. Later, as a result of the in- 

 ability of these beetles to fly, the possibilities of traveling great 

 distances became still more limited, and a relatively large number 

 of species developed in the mountainous regions, where evident 

 upheavals and changes of contour occurred in the past due to 

 extraordinary volcanic and other ordinary physical actions. In 

 the large islands most species are found in very limited areas, 

 such as well-defined mountain ranges, certain valleys, and iso- 

 lated mountains. Other species are found exclusively on small 

 islands, such as Catanduanes, Polillo, Bucas Grande, and Siargao. 

 A very few species range over a relatively large territory ; for 

 example, Pachyrrhynchus orbifer Waterh., which is found over 

 the entire northern part of Luzon, but according to each partic- 

 ular locality is modified into hundreds of varieties and local 

 forms. Another example is P. moniliferus Germ., which is 

 found in the typical form and several very pronounced varieties 

 in Luzon and has subspecies in Mindoro, Polillo, and the Catan- 

 duanes. Instances where a certain species is found in several 



'Wallace, Island Life (1881) 276. 



