302 University of California Publications in Zoology [Vol.19 



turned against the medium selected for a domicile, and as excavating 

 implements have proven very efficient. 



The conclusion upon comparing the large number of free-living 

 species of the genus Sphaeroma with the five or six species for which 

 the boring habit is reported is that this habit is probably of rather 

 recent acquisition in this group, though in Limnoria, with its very 

 extensive distribution for a comparatively small number of species, the 

 wood boring habit may have had a longer history ; it seems to have 

 become so thoroughly established here that Limnoria is not known to 

 live in a free condition. References to the occurrence of fossil rock- 

 boring isopods are not known to the writer, though some search has 

 been made for them. 



OTHER BORING SPECIES OP SPHAEROMIDAE 



The earliest report of the occurrence of Sphaeroma boring into 

 wood or stone seems to be that of Fritz Midler from Brazil. In this 

 case Sphaeroma terebrans Bate was "procured in timber which had 

 been immersed in the sea" (Bate, 1866, p. 28). 



In 1866 C. Spence Bate described Sphaeroma vastator from 

 Madras, taken "from a piece of wood which had formed part of a 

 railway bridge over one of the back waters on the west coast of the 

 [ndian peninsula. The wood was honeycombed with cylindrical holes, 

 from about one-tenth to two-tenths of an inch in diameter, placed close 

 together. In many of these holes the animal was rolled up like a ball 

 (Bate, 1866, p. 30). 



The occurrence of Sphaeroma destructor Richardson (Richardson, 

 1897, p. 105) in wooden piers in the fresh-water portion of the St. John 

 River near Palatka, Florida, 75 miles from the sea, where the water 

 is fresh enough for the growth of the water hyacinth (Snow, 1908, 

 p. 11), is said to be the first reported instance of isopods damaging 

 submerged woodwork in America. Dr. Richardson in describing this 

 says: 



Sections of the wood show that the diameter had been reduced during a 

 period of eight years from 16 inches to 7% inches. The whole surface of the 

 wood was bored with holes averaging in size about 5 mm. in diameter, and in 

 end sections the holes were arranged in concentric rings between the rings of 

 annual growth, showing the little animals' preference for soft pine. Very 

 strong mandibles projecting beyond the labrum most conspicuously provide a 

 perfect equipment for destructive work. 



