Vol. xxvi] ENTOMOLOGICAL NEWS 389 



branch, the dorsal rectal trachea, (rdrti, Idrti), which runs mesad and 

 enters the cavity of the dorsal longitudinal rectal fold. Within this 

 fold this trachea divides and subdivides, but no anastomosis between 

 any of the smallest subdivisions of the right dorsal rectal trachea with 

 subdivisions of the left dorsal rectal trachea have been found, in spite 

 of special search for them. 



A short distance anterior to the origin of each dorsal rectal trachea 

 a lateral rectal trachea (rlrti, llrti), arises, either indirectly from the 

 dorsal longitudinal trachea (cf. text-figure i and right side of Plate 

 XVI), or from the lateral longitudinal trachea (cf. left side of the 

 same Plate), which extends mesad and caudad and enters the lateral 

 longitudinal rectal fold of the same side of the viscus, within which 

 it subdivides. A smaller, posterior, tracheal supply (rlrtu, Urtu) 

 is also received by these lateral rectal folds from branches either from 

 the lateral longitudinal trachea or from the median caudal gill trachea, 

 as may be seen by comparing the right and left sides respectively of 

 Plate XVI. No anastomoses of tracheoles from the anterior supply 

 of the lateral rectal folds with those of the posterior supply have been 

 detected. 



A small posterior tracheal supply for the dorsal rectal fold is re- 

 ceived from the right and left median caudal gill tracheae (tracheae 

 rdrtu, Irdtn of Plate XVI). Here again no anastomoses, either trans- 

 verse or longitudinal, have been found. 



The only anastomosing tracheae which have been discovered are the 

 posterior terminations of the right and left lateral longitudinal trach- 

 eae which, assuming a ventral position, meet on the mid-ventral line 

 ventrad of the alimentary canal; in this anastomosis (anas) take part 

 also a branch from the right and a branch from the left lateral caudal 

 gill trachea. These four anastomosing tracheae, since they lie ventrad 

 to the rectum, have been represented by lines of alternating dots and 

 dashes in Plate XVI. A similar anastomosis in Mecistogaster modcstus 

 has been figured* in No. Ill of these studies and has been found by the 

 writer in transparent living larvae of Hetaerina americana, Argia 

 woesta futrida and Ischnnra t'crticalis; it has not been figured for 

 Anisopterous larvae and may prove to be a characteristic of those of 

 the Zygoptera. 



A comparison of the works of authors who have described the trach- 

 eae of Odonate larvae has yielded the table on page 300. 



The terminal tracheoles, of the tracheae which run into the longi- 

 tudinal rectal folds, enter the epithelium, although whether they mere- 

 ly pass between the epithelial cells or actually penetrate the latter, the 

 condition of the material does not enable one to decide. The diameter 

 of some of these infra-epithelial tracheoles, near their point of final 



*Ent. News, xxii, pi. xvii, fig. 7. 1911. 



