INTRODUCTION. 



The following paper is the result of studies begun more than 

 two years ago at the Entomological Laboratory of the Massachusetts 

 Agricultural College, as a consequence of complaints made to the 

 Hatch Experiment Station of serious injury caused by the Green- 

 house Aleyrodes (Aleyrodes vaporariorum), and the need of more sat- 

 isfactory methods of controlling the pest than those previously 

 known. Mr. J. B. Knight, who was at that time pursuing the grad- 

 uate course for the degree of Doctor of Philosophy at the college, 

 began a study of the different stages of the insect, but having given 

 up the work to accept a position in India, the study of this insect 

 was taken up by the present writer. Mr. Knight's description was 

 briefer than the one here given, and has been used only for com- 

 parison, none of his work having been incorporated in this paper. 



Having discovered in the course of my studies that the Straw- 

 berry and Greenhouse Aleyrodes were distinct species, rather than the 

 same, as was generally supposed, I have extended the scope of the 

 work as previously outlined, to include a discussion of both. At 

 present, there are about sixty-five American species of the genus 

 Aleyrodes known.* Of these, the two species which form the sub- 

 ject of this paper, A. vaporariorum Westw., and A. packardi Morrill, 

 with the Orange Aleyrodes, A. citri Riley and Howard, are the only 

 ones which have thus far proved to be of much economic importance 

 in the United States. A. citri, which was first described from Flor- 

 ida, has been recorded in greenhouses as far north as Michigan,! 

 and Quaintance % states that it occurs generally in greenhouses ; its 

 attacks, however, are almost wholly confined to orange and lemon 

 trees. This species has never been recorded from Massachusetts. 



I have followed the original spelling of Latreille in the use of 



* Including twenty Californian species, the descriptions of which are unpublished at 

 the time of this writing (Psyche, vol. ix, p. 32S.) 



t Davis, Miscellaneous Bull. (Special Bull. No. 2) Mich. Expr. Station, p. 24, (1S96.) 

 % Quaintance. U. S. Dept. Agric, Div. ent., Tech. ser. Bull. No. S, p. 22, (1900.) 



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