214 L- M. HICKERNELL. 



and Ramdohr about the middle of the last century. Lubbock 

 described the digestive organs in Coccus hesperidum. He ob- 

 served the complicated windings in the anterior region and 

 called this complex the internal gland. 



Dufour (1833) described the digestive apparatus of certain 

 Hemiptera but the significance of some of the structures which 

 he described apparently escaped him. In fact, it has been only 

 recently that the digestive systems of any great number of 

 Hemiptera have been worked upon and the true nature of the 

 structural peculiarities of the organs determined. 



Witlaczil ( '85) studied the anatomy of the Psyllidse. In 

 Psyllopsosfraxinicola the digestive canal has many of the peculiar- 

 ities which have been noted in the cicada. 



Berlese (1909) describes the digestive organs of certain scale 

 insects. In these insects the rectum is large and extends anterior- 

 ly as far as the esophagus. This results in a knitting together of 

 rectum and esophagus and also causes the intestine to describe 

 a complete circuit of the abdominal cavity before it finally joins 

 the rectum. This condition, while resembling it superficially, 

 is entirely different from the arrangement found in the adult 

 cicada since in the latter the enormous enlargement affects the 

 mid-gut while the rectum is relatively small. 



Licent (1911) gives an account of the digestive organs in the 

 Cercopidae. In this family there is also a loop made by the mid- 

 gut which curves backward so as to become intimately associated 

 with the anterior part of the canal. Licent believes with Berlese 

 that this complication acts as a filter, allowing the watery part 

 of the food to diffuse directly through the walls of the fore-gut 

 into the cavity of the hind-gut and in this way saves the mid-gut 

 for digestive activity upon the more concentrated food mass. 

 The nutritive substances, greatly diluted with sap, are thus con- 

 centrated and, for the most part, digested in the mid-gut. 



Kershaw (1913) recorded his observations on the digestive 

 organs in Siphanta acuta, a flatid. This form has a large reservoir 

 or crop, which from its junction with the esophagus just within 

 the abdomen, extends anteriorly above the esophagus through 

 the thorax and practically fills the epicranium above the brain. 

 It also extends posteriorly beneath the heart and above the rest 

 of the internal organs, almost to the tip of the abdomen. It is 



