GREAT INCREASE IN THE ORGYIA RAVAGES. 79 



sites belonging to the family of Chalcididce, which were described by him 

 under the name of Tricliogramma? OrgyicB. Another species, re- 

 sembling this so closely as to have been named by him the " brother para- 

 site," Tricliorjramma fraterna, was found by him under conditions that 

 led him to believe that it was also parasitic on the Orgyia. These 

 species have been subsequently referred to the genus Tetrasticlms 

 by Mr. Howard, who is of the opinion that they will prove to 

 be not parasites upon the Orgyia leucostigma larva, but upon a species 

 of Pteromahis which is parasitic upon it. This Pteromalus has been 

 reared by me in large numbers, but, in the uncertainty that attends the 

 numerous described species of this extensive genus, it remains at the 

 present undetermined. 



I have also obtained from the eggs of the Orgyia a minute parasite, 

 which has been generically determined by Mr. Howard as Telenomus. 



A species of Hemiteles is a very common parasite upon the larva in 

 the vicinity of Albany, and in some seasons it has proved to be the 

 principal instrument in arresting its multiplication. 



There is also in my collection a Tachinid fly obtained from an Orgyia 

 in 1879, which differs from the species described by Dr. Le Baron, in 

 that it has two large reddish spots on each side of its abdomen, and that 

 its white tegulae, instead of being translucent, are quite opaque. The 

 Tacliina orgyi(B is not at all uncommon with us. 



The Great Increase in its Ravages, 



That this insect has very largely increased in numbers and in destruct- 

 iveness during the last twenty years is evident to all who have followed 

 its history during that time, or to those who have but recently been 

 drawn to notice it as a new depredator. To what cause, it may prop- 

 erly be asked, is this great increase owing ? 



An unusual abundance of a particular species of insect for a single 

 year is a phenomenon of common occurrence, which can easily be ac- 

 counted for from the operation of well-known natural causes. A 

 remarkable abundance of a species for a term of years is not infre- 

 quent, but soon it relapses into its former paucity and harmlessness 

 before the attack of hosts of parasitic foes, which its great increase invites- 



Not so, however, with the Orgyia. Its conspicuous ornamentation 

 and its assemblage in large numbers render it an attractive object and 

 easily to be discovered by its enemies, and already, as stated, seven 

 different species of insects are known to prey upon it. Scores of the 

 smaller ones {Chalcididce), are often feeding in company within the 

 body of a single caterpillar, and it sometimes seems as if almost every 

 cocoon gave forth the parasite instead of the moth. And yet the 



