454 ANIMALS INTRODUCED UNAWARES 



it was carried to the United States we can only guess, but the 

 early colonists, who are known to have planted apple-seeds 

 from the old country, may have carried it thither. It may 

 have passed from the settlers, with apples, into the hands of 

 trading Indians, and been scattered by them, as they threw 

 away the seeds, along the western trails. The westward 

 spread of the apple, due chiefly to the Indians, may have 

 meant also the spread of the lurker in the apple seed. 



It is easy to realize how large and soft fruit may harbour 

 pests, but less easy to see how evil can lurk in the heart of 

 a tiny seed. Yet the seedsman's traffic, so it has been dis- 

 covered, has been responsible for the transportation to this 

 country of several injurious insects. 



Fig. 79. Douglas Fir Seed Chalcid (female). Enlarged eight times. 

 DOUGLAS FIR SEED CHALCID 



Take the interesting case of the Douglas Fir. The 

 Columbia Red Wood or Douglas Fir is a native of western 

 North America. For ninety years it has been grown in this 

 country, first from seed brought across the Atlantic, and 

 thereafter from seed ripened in Scottish woods. On a single 

 estate, that of Durris in Kincardineshire, 300 bushels of good 

 seed used to be gathered in a season, but in 1 905 the forester, 

 Mr Crozier, had to report that the seed was "not worth the 

 trouble of gathering." And why ? Because, as Dr R. Stewart 

 MacDougall discovered, the kernels of the seeds harboured 

 and had been devoured by myriads of grubs of a Chalcid Fly 



