16 



By 1890 about 20 towns in Massachusetts had become affected, and 

 the State authorities were obliged to take decided action in an attempt 

 to control the pest. From 1890 to 1897 large annual appropriations were 

 made, totalling Si, 200, 000, in an effort to exterminate the moth. It 

 was believed at this time that the native parasite forms "might gradu- 

 ally accommodate themselves to the imported pest, and prove prominent 

 factors in the fight against it. ' 



This campaign confined the moth to certain limits, but did not exter- 

 minate it. Unfortunately the State appropriations ceased in 1899 and 

 the fight was left to the affected towns to carry on. During the next 

 five years the moth spread rapidly and the State authorities were again 

 compelled to take action. The Federal Government also came to the 

 State's assistance, and in 1905 a further attempt was made to control 

 the pests by the introduction of parasitic forms from Europe and Japan. 

 Dr Iv.O. Howard, chief of the Bureau of Entomology, Washington, gave 

 special attention to this phase of the work. He paid three or four visits 

 to European countries, notably France, Belgium, Italy, Germany, Russia 

 and Austria, for the purpose of getting qualified persons to send large 

 quantities of the eggs, larvae, and chrysalids of both the Gipsy and the 

 Brown Tail Moths, which are usually parasitized in Europe, to the speci- 

 al laboratories that had been erected near Boston. On the arrival of the 

 packages at the laboratories the assistants in charge opened them in com- 

 pletelv closed receptacles so as to prevent the escape of possible sec- 

 ondary parasites, and the material was placed in cages or boxes for the 

 breeding of the parasites. 



The Control by Parasites 



The problem of the control of the Gipsy Moth by parasites is a more 

 difficult one than appears on the surface. From extensive studies of the 

 life history of the moth it has been determined that the probable potenti- 

 al rate of increase is 250-fold annually. On account, however, of the 

 heavy death rate from various causes the actual rate of increase is only 

 from 6 to lo-fold. 



The problem \vas then to secure sufficient parasites to keep the in- 

 sect in control. In other words, if the increase annually be 6-fold, 

 five out of every six insects, either egg, caterpillar, or pupa, or 83t,3 per 

 cent would require to be parasitized.. If the increase be lo-fold, nine 

 out of ever}' ten, or 90 per cent, must be parasitized. To rely entirely 

 upon egg parasites, such as Anastatus or Schedius, to destroy such a 

 large precentage of the eggs w^as out of the question, for these parasitiz- 

 ed only the upper layer of eggs in each mass. It became necessary, there- 

 fore, to call in the aid of the parasites affecting the caterpillar and the 

 pupa. Consequently efforts have been made to secure a sequence of para- 

 sites from foreign countries so that every stage of the moth is subjected 

 to attack, and which would bring up the death-rate to 85 or 90 per cent. 



