THE CANADIAN ENTOMOLOGIST. 173 



NOTE ON THE RESPIRATION OF ALEURODES CITRI. 



BY C. W. WOODWORTH, UNIVERSITY OF CALIFORNIA. 



The effort to control the " white fly " of the orange (Aleurodes citri) 

 by hydrocyanic acid gas, naturally suggested an inquiry into the respira- 

 tion of these insects. The author was enabled to pursue this inquiry, 

 while recently in Florida, under the auspices of the Florida Agricultural 

 Experiment Station. 



The only account of the organs of respiration in the young of this 

 family is a brief note with a figure in Burmeister's Handbuch, which is 

 very incomplete and not entirely accurate. Some very interesting and 

 quite unique features are presented by these insects, not the least of which 

 are the breathing folds, that are very conspicuous structures, and have 

 been heretofore incorrectly interpreted. The view suggested by Riley and 

 Howard (Insect Life, 1893, Vol. 5, pp. 219-226), that the anterior folds 

 represent the original division between the head and thorax, is the one 

 usually accepted. In reality they are wholly thoracic in position, being 

 nearer to the pro-mesothoracic line than to the head-thoracic boundary, 

 and they are by no means vestigial structures, but specially developed 

 organs of respiration. 



The necessity of these organs is very evident when it is noted that 

 the spiracles open ventrally, and that the body is cemented to the leaf. 

 The insect is nearly transparent, and very inconspicuous as it lies upon 

 the leaf, but if the leaf is bent so that air is admitted beneath it, the insect 

 immediately becomes whitish. An examination of the inverted insect 

 under the microscope shows the ventral surface to be marked off into 

 polygonal areas, with many round regions resembling glands. These 

 correspond exactly with the cells and stomata of the leaf, and are, in fact, 

 a mould of the surface upon which the insect rested, produced doubtless 

 by the hardening of the secretions of the marginal glands. 



The breathing folds are the only passages between the outside air and 

 the spiracles; and they are really structures showing quite high specializa- 

 tion. The surface of the lumen of the groove is armed with minute scattered 

 chitinous papillse, and thus differs strikingly from the structure of any other 

 part of the skin of the insect. The outer opening is guarded by a pair of 

 oblique combs. They are produced by a modification of the serrations 

 that elsewhere form the border of the body, and recall the guard-combs 



