304 Annals Entomological Society of America [Vol. ITT. 



Longiuidinal muscles are absent in the fore-intestine and 

 in the colon and rectum. 



Gastric caccae are replaced by a caecal gland, which girdles 

 the median portion of the esophageal valv^e. 



There are five Mali)ighian vessels of similar form and struc- 

 ture, two extending cephalad and three caudad. 



The rectum is prolonged into four slightl}^ eversible papillae, 

 which are homologous with the anal tracheal gills of Cule.x and 

 related forms. 



The epithelium of the mid-intestine is divided into five 

 distinct regions; an anterior one giving rise to the peritrophic 

 membrane, a caecal gland, a small area of long glandular cells, 

 a long stretch of large polygonal cells, and the posterior region 

 of tall slender cells. The so-called mucus cells are abundant. 

 There is no regeneration of the epithelium of the mid-intestine 

 at the time of feeding. During a fast, secretions are not stored 

 up in the epithelial cells but are continually poured out and if 

 the fast be prolonged the cells may completely break down. 

 The peritrophic membrane is secreted by a definite group of 

 cells at the anterior end of the mid-intestine. 



At each larval molt the epithelium of the mid-intestine 

 is completely renewed. The old cells are not cast off as a whole, 

 but the degeneration begins next to the lumen and continues 

 until the whole cell is broken down. This degeneration begins 

 in the posterior region of the mid-intestine and proceeds forward. 



Regeneration is from scattered embryonic cells which lie 

 in the angles at the base of the epithelial cells. The regenerated 

 epithelium of the mid-intestine is mature by the time the larval 

 skin is cast off. 



