366 AN ATTEMPT TO CONTROL INSECT PESTS 
necessary first to establish, then to disperse, and therefore no small colonies 
were put out. In 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 New parasites 
hrs | recorded. species bred. bred. 
| Gipsy Moth :— 
Braconidae BG tio oct 10 2 3 
Ichneumonidae : 
Primary 50C 30 oe 11 3 a 
| ? Secondary ... 560 ane 9 — — 
Chalcididae as one eee 6 1 4 
| Tachinidae oD ed ewe 20 4 6 
56 10 20 
| Brown-tail Moth :— 
| Braconidae 260 nO 56 13 1 1 
Ichneumonidae : 
Primary add oe RE 2) 3 1 
? Secondary ... S06 An 3 — — 
Chalcididae a0 200 500 y | 1 d 
Proctotrypidae ... bc ah 1 1 | — 
Tachinidae aoe 006 se ic 3 13 
42 9 19 
| 
There were 56 previously recorded parasites of the gipsy moth, of which 
10 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 were therefore let loose in small colonies, Useful results were 
also anticipated from a predaceous beetle, Calosoma ; this was found to remain 
for several years where placed before dispersing. In the case of an egg parasite, 
Anastalus, the dispersal rate was shown to be only a few hundred feet per year. 
In Monodontomerus, the male and female couple in the host, so that fertilisation at 
least takes place, favouring 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. Monodontomerus spread 200 miles in 5 years, but is exceptional. 
Tachinids are rarely, if ever, parthenogenetic. 
