.VORTH AMKRICAN ODONATA. 177 



it joins the labium. The development of the salivary glands begins 

 in a late nymphal stage. 



The mid-gut (chylific ventricle) extends from the second to the 

 hind part of the seventh abdominal segment. Its walls are thicker 

 than those of the fore-gut, and are transversely ringed. The open- 

 ing between the fore- and the mid-gut is valvular, so formed by the 

 hind end of the fore-gut extending a short distance into an invagina- 

 tion of the front end of the mid-gut. There are no appendages 

 (cfficfe) to the mid-gut. Faussek (7) has described the histological 

 structure of the mid-gut. The epithelium consists of high, very 

 narrow, cylindrical cells, and does not form folds ; between these 

 cells are many fairly large glands (crypts) whose cell-nuclei, in con- 

 tradistinction to those of the epithelium proper, show mitosis. Ex- 

 ternal to the epithelium is a structureless membrana propria, then 

 in succession outwards, a circular muscle, a connective tissue and a 

 longitudinal muscle layer. This description applies to the mid-gut 

 of Aeschnid, Libellulid and Agrionid larvse, and to the imago of 

 Dlplax striolata. 



Griffiths (Physiol, of Invert, p. 94, 1892) finds the fluids within 

 the mid-gut (secretions of the crypts) to be always slightly alkaline ; 

 an infusion of about twenty such mid-guts readily converted starch 

 into glucose and digested fibrin. 



The hind-gut (rectum) extends from the seventh abdominal seg- 

 ment to the anus. No valve exists between mid- and hind-gut, but 

 the anterior extremity of the latter is marked by the attachment of 

 the Malpighian tubules, which may be regarded as appendages of 

 the hind-gut. The walls of this part are also thicker than those of 

 the fore-gut. A constriction divides the hind-gut into two parts, 

 the anterior part being of larger calibre, and having on its inner 

 surface longitudinal ridges, representing the branchial ridges of the 

 nymph. These ridges fade away in the posterior part of the hind- 

 gut. 



The Odonata are rapacious and carnivorous, both as nymphs and 

 as imagos, the former feeding on young fish, tadpoles, aquatic insects 

 and probably many other water-dwelling animals. The food of the 

 imagos consists mainly of insects of all orders, including their own, 

 but especially of soft-bodied Diptera and Hemiptera. Dr. Abbott 

 found dragonflies feeding on the decomposing remains of a calf in 

 New Jersey, in October ("Upland and Meadow," p. 316). The 

 cannibalistic habits of the Odonata are shown by the following facts : 



TEANS. AM. ENT. SOC. XX. (23) AUGUST. 1893. 



