16 CLASSIFICATION OF THE ALEYRODIDiE. 



is not only a prominent labium in this stage, but it is armed with 

 taste sensoria. The function of the nervous system is riot suspended 

 during the entire life of aleyrodids, but as a similar state of affairs 

 is found in such forms as the Muscida?, this indicates little. The di- 

 gestive system, with a few alterations, seems to pass over from the 

 larva to the adult. The reproductive organs develop in the pupal 

 stage and some, though not extensive, histolysis occurs. The adults 

 without question feed, for they may be seen in the act and the honey- 

 dew excreted is a further evidence of this. It would appear that 

 during the first part of the last (pupal) instar, the insect lives a life 

 similar to that led in the earlier stages. During the last part, how- 

 ever, activity seems to cease for a short time, while transformation 

 takes place within the larval skin. This change appears to be gradual 

 in some respects and the metamorphosis in the Aleyrodidas may be 

 considered as of an intermediate type. 



The adult emerges through a T-shaped opening on the dorsum of 

 the pupa case. A short time before this opening is noticed, the in- 

 sect maj'^ be seen fully formed within the case, and as it crowds in 

 from the edges the rupture takes place. The thorax is first to emerge, 

 followed by the head. The antenna? and legs are next worked free 

 and the insect assumes an upright or recurved position similar to that 

 adopted by man}' other insects in this process. Finally the abdomen 

 is worked free and the insect moves away. The time normally occu- 

 pied in this process is only a few minutes. Where the pupa cases 

 are hard, however, a much longer time is required and it is not un- 

 common to see insects struggle for hours and finally die without being 

 able to free themselves. After the adults have left the case it requires 

 some minutes for the wings to expand and the colors and waxy secre- 

 tion to develop. Morrill and Back*' have given careful observations 

 on the act of emergence of Aleyrodes citri, which in the main agree 

 with ours here recorded. They also give the effects of temperature 

 and humidity on the emergence of that species, stating '' that temper- 

 ature and not humidity is the more important factor governing 

 emergence in Florida." On the other hand, Mr. R. S. Woglum, of 

 the Bureau of Entomology, who has made extensive observations on 

 this species in India and the Orient, is of the opinion that humidity 

 is the governing factor. He states that the emergence of the flies, 

 at least in any numbers, always follows a rise in humidity, while the 

 optimum temperature under these conditions, together with a low 

 humidity, seems to check emergence. 



CLASSIFICATIOIT. 



Until recently only two genera, Aleyrodcs and Aleurodiciis^ were 

 recognized for the family Aleyrodida?. AVithin the past three or 

 four years, however, there have been established the additional genera 



