( xlvii ) 



Wagner. Hagen, &c, against its introduction into America, 

 were inherently weak from the biologic side. They are based 

 on the average or normal period of summer development of 

 about seven weeks from egg to adult, and ignore the important 

 bearing of exceptional retardation in development whereby the 

 puparia of one summer remain latent and only give forth the flies 

 in tin ■ mmmer of tiie ensuing year. This fact, 



recognised by Harris I s -"- . Prof. Riley said he had evidence 

 of in America in garnered straw, and it was proved by Wagner 

 himself to have occurred in Germany in field-stubble. It was 

 more apt to occur, however, in straw kept dry and packed 

 than in stubble or exposed straw, and is in keeping with 

 many other similar cases of retarded development in insects, 

 some remarkable instances of which he called attention to 

 before the American Association for the Advancement of 

 Science in 1881. It destroyed Hagen's main argument, 

 rendered the introduction of the species possible at almost any 

 season, and made its introduction to America by the Hessians 

 who left Portsmouth April 7th and landed June 3rd, 1777, on 

 Staten Island, quite probable and plausible from biologic 

 grounds. All the facts as to the history of the insect in Great 

 Britain indicated its recent introduction. The lengthy inquiry 

 carried on at the request of the Privy Council by Sir Joseph 

 Banks a century ago, a lull record of which will be found in 

 Young's ' Annals of Agriculture,* l\:c. (vol. xi., 1789, pp. 406- 

 613), proved quite conclusively that the insect was not here 

 then ; and there was no reason to suppose that since then it 

 would long have eluded detection whether by intelligent farmers, 

 or by entomologists like Kirby, Curtis, and Westwood. The 

 first authentic record of its appearance in this country was 

 that by Miss E. A. Ormerod last year (1886), and, as so often 

 happens after the first announcement of a discovery, when 

 public attention has been strongly called to a subject, hosts of 

 observers have been on the qui rice for the insect who would 

 otherwise never have looked for it. As a consequence it had 

 been detected during the past summer along the eastern coast 

 up into Northern Scotland ; and this wide distribution would 

 indicate that it had been at work unnoticed for some years 

 previous to 1886, though it may also be accounted for by the 



