318 



Habits of the Greenhouse White Fly 



Breathing folds (Figs. 26, 33). There is a pair of anterior folds 

 opening ventro-laterally opposite the anterior pair of thoracic spiracles. 

 They are continued alongside the thorax to the first one or two abdom- 

 inal segments. In the living insect, the passage leading to the exterior 



Fig. 33. Ventral view of fourth instar. 



appears to be a tube (Fig. 33), the floor of which is formed of wax, so 

 that in specimens which have been treated with a wax solvent, the 

 tubes have become simply grooves (Fig. 26). There is also a posterior 

 fold extending from the middle of the posterior margin to the vasiform 



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Fig. 34. Opening of posterior fold. 



Fig. 35. Opening of thoracic fold. 



orifice, which communicates with the posterior spiracles. The character 

 of the margin at the external openings of these folds is peculiar (Figs. 

 34, 35). Later, the body shrinks away from the cuticle, and the develop- 

 ment of the adult organs (eyes, wings, legs, etc.) begins. In sections 



