470 ANIMALS INTRODUCED UNAWARES 



the Zebra Mussel as a colonist has been remarkable. It 

 has spread from one locality to another until it has stations 

 in some twenty English counties. In Scotland it is common 

 in the Paisley Canal and in the Forth and Clyde Canal, 

 where it used to be found "in vast abundance." Even in 

 the most out-of-the-way places it has succeeded in obtaining 

 a hold and in making headway ; it is a common member 

 of the fauna of water-pipes, and in 1912 a stoppage of the 

 water supply at Hampton-on-Thames led to the discovery 

 that the diameter of the 36-inch main for unfiltered water 

 had been reduced to 9 inches by masses of Zebra Mussels 

 which were growing attached to the inside of the pipe. 

 Ninety tons of the shells are said to have been removed 

 before the main was again put in working order (see Fig. 68, 



P- 415). 



Other Molluscs have been carried with timber, such as 

 the West Indian Bulimus undatus, which arrived in Liver- 

 pool attached to tropical timber and alive, and is said to 

 have formed a colony near that city. But success seldom 

 greets such casual voyagers. 



The characteristic travellers with timber are the boring 

 insects, especially the tunnelling Beetles, whose larvae are 

 long-lived and lie unobserved and secure in their burrows 

 until the time of their transformation and emergence. 



LGNG-HORNED INVADERS 



Of invading Beetles the most interesting in appearance 

 are the striking "long-horned" Beetles (Longicornia), easily 

 recognized by the extraordinary length of their antennae, 

 which may twice or three times exceed that of the body. 

 Often their wing-cases display rich patterns and colours, and 

 this and their size make them conspicuous visitors. Not 

 many native beetles can rival in appearance the oak-boring 

 Timber Beetles or Capricorns, Cerambyx heros and Cerambyx 

 cerdo, with their rich brown wing-cases and their fine 

 antennae, in the male almost twice as long as the inch-and- 

 a-half long body. Their distribution in England betrays 

 their origin. By far the greatest number of specimens has 

 been found in the neighbourhood of dockyards, whither 



