1906.] 



A New Enemy of Douglas Fir. 



619 



time on the Douglas Fir trees, as also on the top of the seed- 

 beds some time after sowing, these last having most likely 

 issued from seed which had been sown. 



Each infested seed of the Douglas Fir contains only one 

 larva, which nourishes itself on the reserves contained in the 

 seed. The seed bears no external mark of the internal presence 

 of the Megasiigmus larva. Pupation takes place in the seed, 

 there being no cocoon. In a number of the seeds which I 

 dissected, and from which Megastigmns adults had issued, 

 the contents of the seed had been devoured and only the outer 

 brown testa or seed - coat remained, surrounding the inner 

 white-coloured perisperm sheath. In other seeds, on dissection, 

 I found the larva, and where it was full-grown and the seed- 

 contents destroyed, the white-coloured perisperm sheath sur- 

 rounding the larva bore a close resemblance to a cocoon. 



V 



fi 



Fig. I). — Attacked seed of Pseudotsuga Douglasii from which the 

 adult has issued (natural size and twice magnified orig.)- 



Starting from the first laid eggs of the spring brood of 

 Megastigmus, the generation can probably be reckoned as an 

 annual one. From Douglas Fir seeds received in May, I bred 

 out males and females during May and June. Seeds of the 

 same age dissected then also revealed larvae. In dissection 

 of seed during July, August, September, and October, I never 

 failed to find healthy larvae, and now in November I can 

 still get larvae, and all this with seed material from Douglas Fir 

 cones harvested in October, 1904, and having their seed 

 extracted in 1905. This can probably be accounted for partly 

 by the considerable irregularities in time of hatching of eggs 

 and coming to maturity known to occur in other insects with 

 eggs laid at or about the same time, partly perhaps by the life 



