THE VAPOURER MOTH 77 



marks of the disorders which afflicted the silkworms, traced 

 the modes of infection, and at length discovered how to 

 separate sound from infected eggs, and how to maintain a 

 race of silkworms free from disease. While we learn from 

 this memorable story what great and beneficent results may 

 be accomplished by the genius and unflinching labour of 

 one man, we learn also lessons more applicable to the ordinary 

 affairs of mankind, where neither genius nor heroic sacrifices 

 can be counted on. We learn that the experimental habit 

 of mind may be more productive, even in the biological 

 sciences, than much professional learning, and that true 

 science can win for any nation rewards for which no price is 

 too high. 



18. THE VAPOUEEK MOTH {Orgyia antiqua) 



Caterpillars of this common species are now and then found 

 in gardens in great abundance, devouring the leaves of many 

 different trees and shrubs. When the vapourer has swarmed 

 to such a degree as to cause much damage, it often falls off in 

 numbers, and escapes notice for years together. This occa- 

 sional abundance is a common thing with insects. Sometimes 

 it is due to temporary freedom from the attacks of ichneumons 

 and other parasites (see gooseberry saw-fly, p. 94), but this 

 explanation will not meet every case. Vapourer caterpillars 

 usually appear for the first time in the year towards the end 

 of June, and are perhaps more often discovered on roses than 

 other plants ; a second brood is often hatched out in 

 September. They are of active habits, running about with 

 considerable agility upon occasion, and making their way 

 without difficulty to distant trees and shrubs. Owing to their 

 accommodating tastes in the matter of food, they are very 

 easily reared in captivity, if simple precautions are taken to 

 prevent them from straying, and few of our insects are better 

 worth close observation. 



The caterpillar is often about 50 mm. (2 in.) long when full- 

 fed, but a certain proportion never attain these dimensions, 

 pupating when only about 30 mm. long. These smaller 

 caterpillars produce male moths, the larger ones female. The 

 caterpillar is easily recognised by its conspicuous coloration. 



