3° 



of a few minutes so that its long axis formed an angle of ninety de- 

 grees to its original position. 



Between the moults in all the immature stages — considering 

 hatching from the egg as a moult — lateral growth of the body is not 

 appreciable, increase in size seeming to result almost entirely from 

 growth in thickness. 



During the last few days of pupal life the insect does not feed or 

 perceptibly increase in size, and the developing imaginal characters 

 can be more or less distinctly seen within. It is at this time, only 

 that the Aleyrodes is a true pupa in the sense the word " pupa " as 

 used in other Holometabola, or insects with complete metamorphosis ; 

 thus what is known as the pup a case is in reality the last larval skin. 



In all the immature stages there is exuded from the vasiform 

 orifice at intervals a colorless liquid similar to the honey dew of 

 aphids. Sometimes this excretion collects in large viscid globules 

 immediately below the insect secreting it, apparently suspended 

 either by the hairs on the leaf or by the dorsal spines of the insect. 

 The cause of the insects feeding almost exclusively on the under 

 surface of the leaves is apparent. If they should attack the upper 

 surface of the leaves in large 'numbers they would cause their own 

 destruction, for in this case the honey dew, instead of dropping to 

 the leaves below, would spread out over their bodies and serve as 

 food for fungi, the mycelia of which readily penetrate the tender 

 skins of the insects themselves. 



Adults. The adults emerge through a T like opening in the 

 pupa case. The integument splits along the middle of the dorsum 

 from the anterior end of the body to the base of the abdomen, 

 where it joins a transverse split which follows the line of segmenta- 

 tion, reaching nearly to the lateral margin of the case on each side. 

 A newly emerged adult is devoid of wax secretion, the wings are 

 folded up like crumpled paper, and the legs are delicate and much 

 twisted. In a short time secretion of wax appears, the wings unfold 

 and the legs straighten. The wings are rarely used unless the insect 

 is disturbed, and then only for short, more or less erratic flights. It 

 is probable that the wind plays an important role in their distribu- 

 tion out of doors. In the laboratory single specimens on isolated 

 plants have been observed to remain for days at a time on a single 

 leaf. 



