472 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvii. 



was almost killed b}- the multiplication of a few meml^ers of one 

 species within a year. Already these insects are being fought as a 

 pest in the conservatories. On the other hand, the author has 

 frequently found colonies of Aleyrodes parasitized to an extent 

 which indicates that nature herself will check the threatened danger. 

 The chief reason why these insects might become trouljlesome econom- 

 ically is that man}" of them are omnivorous in food habit, and, not 

 being capa])le of strong flight, would, under stress, readily become 

 habituated to the nearest food plants. 



But it is not from the point of view of the economic entomologist 

 that the author has l)egun the study of the Aleyrodida?. It is rather 

 with the hope of throwing some light on their somewhat ambiguous 

 zoological position through a detailed study of their structure and 

 life history that the work has been undertaken. The curious meta- 

 morphosis of the Ale3n-odids is not definitely understood; whether it 

 should be called "complete" or "incomplete" is certainly still a 

 mooted question. In the present paper the author uses the termi- 

 nology which is already in vogue in the literature of this group, though 

 the terms "pupa" and "pupa-case" are arbitraril}" employed when 

 applied to a family in which the metamorphosis ma}" be incomplete. 



With this structural and developmental study as an idtimate aim the 

 author has made a l)eginning in the study of the Aleyrodidse. An 

 acquaintance with species has necessarily 'been the first step in the 

 work, and this paper is therefore primarily systematic in character. 



The geographical range covered in collecting the species herein 

 described will be Imt briefly indicated here, as the exact localities are 

 given in the text for each species described. It may here be said, 

 however, that all the collecting has been confined to California, speci- 

 mens having been taken in the Santa Clara Valley (Santa Clara County), 

 on the slopes of the Santa Cruz and Sierra Morcna ranges (Santa Clara 

 and San Mateo counties), in Golden Gate Park, San Francisco, in the 

 San Ramon Valley (Alameda County), at the l)ase of Mount Diablo 

 (Contra Costa County), and to a small extent in Alameda, Napa, and 

 Mendocino counties, in southern California, and in the Yosemite Val- 

 ley. King"'s Mountain, often referred to as a collecting ground, is in 

 San Mateo County and Black Mountain in Santa Clara County. 



The immature stages may be looked for upon either surface of the 

 leaves, appearing upon plants as dissimilar in hal>it as the plantain and 

 the oak. Most of the species are omnivorous, while a few seem to be 

 confined to a single host. It would appear from material collected at 

 points scattered from the base of the coast range to its summit that in 

 the distribution of the Aleyrodidte in this range there are no zones 

 defined by altitude, the author having found the greater number of 

 species collected, characteristic of the entire region from valley to 

 summit. 



