64 INSECTS AND MAN 



branches and transform to the adult stage. Professor 



o 



Riley says : " There are few more beautiful sights than to 

 see this fresh-forming cicada in all the different positions, 

 clinging and clustering in great numbers to the outside 

 lower leaves and branches of a large tree. In the moon- 

 light such a tree looks for all the world as though it 

 were full of beautiful white blossoms in various stages of 

 expansion." The adult stage only lasts for a period of 

 about six weeks, and, as a rule, their disappearance is as 

 sudden as their appearance. In this short period, however, 

 the females contrive to do a considerable amount of damage 

 to various trees, by reason of their peculiar egg-laying 

 habits, oak, hickory, and apple being especially favoured. 



The gipsy moth, Porthetria dispar, is an insect that is 

 worthy of mention wherever the subject of economic 

 entomology is mooted, not so much on account of its doings 

 in its native country or countries, but because of the 

 enormous havoc it has wrought in the land of its adoption 

 America. Well known in Central and South Europe, the 

 range of this moth also extends over the temperate regions 

 of Asia to Japan. Though rare in England, it is a serious 

 pest in some parts of France, Germany, and Russia; its 

 southern limit seems to be Algeria, where no doubt it has 

 been introduced from France. As a forestry pest the insect 

 is notorious, and as long ago as 1720 it and its injuries 

 were well known. 



The history of the introduction of this moth into America, 

 especially in the light of subsequent events, reads more 

 like some wild romance than the entomological tragedy 

 which it was. In 1869, Professor L. Trouvelot was con- 

 nected with the astronomical observatory at Harvard 

 University, and he combined with his astronomical pursuits 

 a taste for entomology, his special hobby being the cultiva- 

 tion of wild silkworms. At that time the silkworm disease, 

 known as pebrine, was decimating the inmates of the 

 sericulture establishments of Europe, and the Professor, by 



