PREFACE. 



The series of articles here presented in bulletin form under the title 

 " Some insects injurious to garden crops," is in continuation of work 

 done by the writer in previous years on the same subject, the results 

 of which have been announced in different publications of this Depart- 

 ment, and are for the most part based upon observations which have 

 been made during the year 1899, although many of the species treated 

 were under more or less continuous observation prior to that time. 



Some of the species of insects which are considered are more or 

 less spasmodic or sporadic in the nature of their attack and injurious 

 only in seasons which have been unusually favorable to their increase. 

 A certain proportion of these are for this reason of secondary impor- 

 tance, economically speaking, since in ordinary } r ears of comparative 

 scarcity they find nutriment sufficient for their needs in various wild 

 plants and weeds, being driven to attack cultivated or other useful 

 plants only in their seasons of greatest abundance. Some few of 

 these are as yet comparatively little known, having done no material 

 damage, but several are increasing in noxiousness and those which 

 have never assumed great importance are liable to become so at any 

 time, at least periodically or locally. Certain of the species under 

 consideration, however, are of the highest economic importance when 

 they occur in excessive numbers, and two of these, the destructive 

 green pea louse and the fall army worm, have, been among the most 

 troublesome pests of the past year. 



As in the case of previous general articles on insects affecting garden 

 and orchard crops, the writer has endeavored to treat each species in 

 all its relations, descriptive, historical, biologic, and economic. An 

 effort has also been made to furnish not alone lists of exact localities 

 in which each species has been captured or observed at work, but to 

 define as nearly as possible from these data its geographic range, 

 whether an inhabitant of this or that life area, and whether the natural 

 range has been extended by a corresponding increase in the cultivation 

 of its food plants and by commerce. 



A series of investigations on certain species of insects which attack 

 cruciferous and cucurbit crops was planned for the season, but was 

 necessarily postponed on account of the scarcity of the insects them- 



5 



