566 



AN ATTEMPT TO GONTKOL INSECT PESTS 



uecessaiy first to establish, thou to disperse, and therefore no siniiU colonies 

 were put out. lu some cases introduced parasites were found again after having 

 been lost sight of for three or four years, and some species now lost may in 

 this way reappear. 



The known parasites are enumerated below in three columns : the number of 

 species recorded by previous authors is shown in the first ; the previously 

 recorded [species which were actually bred from sendings from abroad are in the 

 second : while new ones bred from these consignments are in the third. 



' 



Previously 

 recorded. 



Recorded 

 species bred. 



New parasites 

 bred. 



Gipsy Moth ;— 



Braconidae 



Ichueumoaidae : 



Primary 



? Secondary 



Chalcididae 



Tachinidae 



Brown-tail Moth : — 

 Braconidae 

 Ichneumonidae : 



Primary 



V Secondary 



Chalcididae 



Proctotrypidae 



Tachinidae 



lU 



11 



9 



6 



20 



2 

 3 



1 



4 



3 



7 



4 

 G 



56 



10 



20 



IB 



9 

 3 



1 



7 



1 



3 



1 

 1 

 3 



1 



1 



4 



13 



42 



9 



19 



There were 56 previously recorded parasites of the gipsy moth, of "which 

 l(t were reared, and 20 more found, giving a total of 76 species ; while of the 

 brown-tail moth, 42 had been recorded, of which the authors bred 9, together 

 with 19 new ones, making a total of 61 different parasites. 



As the two moths were themselves liberated by accident, it was thought that 

 it would be easy to establish a parasite if enough specimens were obtained ; the 

 species reared Avere therefore let loose in small colonies. Useful results were 

 also anticipated from a predaceous beetle, Culosoma ; this was found to remain 

 for several years where placed before dispersing. In the case of an egg parasite, 

 Aiuitilutus, the dispersal rate was shown to be only a few lumdred feet per year. 

 In Monudontomerus, the male and female couple in the host, so that fertilisation at 

 least takes place, favoru'ing distribution. Many hymenopterous parasites (and 

 very likely all) are capable of parthenogenetic reproduction ; some are 

 thelytokous (producing females only), and so easy to rear ; others are arrheno- 

 tokous (producing males only), but couple with their offspring and give a good 

 fertile race. Monodontumerus spread 200 miles in 5 years, but is exceptional. 

 Tachiuids are rarely, if ever, parthenogenetic. 



