Vol. xxvi] ENTOMOLOGICAL NEWS 387 



sophagus is marked by two longitudinal streaks of blackish pigment 

 corresponding to the areas of contact with the right and left dorsal 

 tracheal trunks. At mid-length of the oesophagus, at the level of the 

 hind margin of the head, is, on each lateral surface, right and left, a 

 salivary gland with a delicate duct running cephalad. The gizzard lies 

 in the first abdominal segment; its chitinous armature, in larva no. 4, con- 

 sists of sixteen longitudinal folds, each of which bears chitinous teeth. 

 In eight of these folds the teeth, near the posterior end, tend to in- 

 crease from one to two rows, while in the other alternating eight folds 

 the teeth are arranged in a single row throughout. The teeth of the 

 various folds are subequal in size, but in each fold tend to become 

 larger caudad. The formula for the gizzard armature may be written 

 8 (F 14-17, f 11-14)* The hind end of the stomach and the place of 

 attachment of the Malpighian tubes lie near the articulation of the 

 fifth and sixth abdominal segments. The ileum extends to the seventh 

 segment. 



The rectal epithelium presents three longitudinal folds, one which is 

 dorsal and a little to the left of the median plane, a second is left 

 latero-ventral, the third is right lateral. Their relative positions may 

 lie best seen in a cross-section of the rectum (PI. XVII, fig. i). The 

 epithelium is interrupted by three, longitudinal, thinner, pigmented 

 areas, one of which is nearlv midventral (mupa) and lies immediately 

 to the right of the attachment of the left latero-ventral fold, a second 

 (rlpa) is immediately dorsal to the right lateral fold, the third (II pa} 

 is to the left of the dorsal fold. These three pigmented areas are 

 homologous with the three "non-cellular longitudinal bands" of the 

 rectum of the larva of Mecistogaster modestus'f and with similarly 

 placed bands in the recta of larvae of Lcstes rcctangularis, Argia 

 moesta putrida, A. talamanca, Ischnura verticalis, etc. Both anterior 

 and posterior to the three longitudinal rectal folds in Thaumatoncura 

 larva, the gut epithelium is very much thinner for its entire circum- 

 ference, equaling, or nearly equaling, in thinness that of the three 

 longitudinal pigmented areas, and containing also much pigment. 



Tracheal System. The arrangement of the larger tracheae of the 

 dorsal side of the body is shown in Plate XV. It corresponds, except 

 in a few minor details, with our figure** for the tracheae of Mecistogas- 

 ter modcstus larva and those of Coleff and of BervoetsJ for a larva of 

 "Agrion." The chief difference between the present results and those 



*Cf. Higgins, Proc. Acad. Nat. Sci. Phila. 1901, pp. 132, 133. 



fEnt. News, xxii, pp. 452, 453, pi. xvii, fig. 10, 1910. The description 

 of them as "non-cellular" may not be justified when material in better 

 condition is examined. 



**Ent. News, xxii, pi. xvii, fig. 8. 1911. 



ttjourn. Appl. Micros. & Laby. Meth. VI, pp. 2224-5, figs. 7, 8. 1003. 



JAnnales Biol. Lacustre, VI, pp. 16, 17, 20, figs. 1-3. 1913. 



