EXTERNAL ANATOMY 37 



described by Pergande as wanting, while in Taehardia the 

 mesospiraeles leave their normal position during nymphal devel- 

 opment and through a readjustment of the bag-like body assume 

 a position near the anus. 



Peritreme. — The spiracles of most insects are surrounded by 

 a thickened area of cuticle which forms a rim about the opening 

 and is known as a peritreme. This rim varies somewhat in form, 

 but in most coccids is simply a circular plate or may be wanting. 

 The portions of the peritreme bordering the two sides of the 

 opening or slit, the cephalic and the caudal, may be modified into 

 lips or labiae for closing the spiracle. 



Spiracularia. — The prominent parademe extending from the 

 ental surface of the peritreme into the body cavity in certain 

 coccids may be known as the spiracularia. They are distinct in 

 Icerya and Monophlebus, serve for the attachment of muscles, and 

 are so far as known peculiar to the thoracic spiracles. 



Cavaera. — The tracheal tube connecting with each spiracle, a 

 spiracular trachea, is frequently expanded in the coccids into a 

 chamber of varying size and shape. This chamber is usually 

 trumpet-shaped or globular and its walls are generally smooth. 

 not transversely striate like the ordinary tracheal tube. This 

 structure may be known as the cavaera. It is also known as the 

 collar chamber. The cavaera constitutes the greater part of the 

 structure usually described and figured by students of coccids as 

 a spiracle. This is particularly true of species of Lecaniinae. 

 The term spiracle is limited here as with other insects simply to the 

 opening. There are folds sometimes present in the cavaera which 

 serve for closing the spiracle, these should not be confused with 

 the labiae which are modifications of the peritreme. 



Abdominal Spiracles.^ — The abdominal spiracles are generally 

 smaller than those of the thorax and may be provided with or lack a 

 distinct peritreme. The normal . number of abdominal spiracles 

 for insects in general is eight pairs, a pair on each of the first eight 

 abdominal segments. When less than this number is present, it 

 is due to the reduction or fusion of the first abdominal segment 

 with the adjacent segment and the loss of its spiracles or the 

 atrophy of the spiracles or their loss through the increase in size 

 and the encroachment of the metathorax or the atrophy of the 

 spiracles at the caudal end of the abdomen. Since the abdomen 

 is not used extensively in classification, it is not strange that the 

 number of records of the presence of abdominal spiracles in coccids 

 is not large. They have been recorded more frequently from 



