64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



same level as the cement glands ; it has the shape of a pipe and bears 

 on its distal end the spermathecal gland (Spg). The receptaculum 

 was examined in all three species but no differences have been found. 

 In the classification of the Scolytidae, based on the female repro- 

 ductive organs by Nuesslin, Gnathotrichus would fall in a group to- 

 gether with the genus Thamnurgus Eichhoff. 



The Alimentary Canal 



The alimentary canal was fully investigated in Gn. materiarius 

 Fitch, the proventriculus in Gn. retusus Lee. and siilcatus Lee, also. 

 The whole alimentary canal of Gnathotriclnis is illustrated in figure 34, 

 the proventriculus in figure 35. 



The alimentary canal is a tube extending from one end of the 

 body to the other. As in most of the mandibulary insects, three main 

 divisions are clearly defined. These are termed the fore, mid, and 

 hind intestine (fig. 34, A, B. C). The ectodermal origin of the fore- 

 and hind intestine are well illustrated by the occurring chitinizations. 



Fore-intestine. — On the fore-intestine the following consecutive 

 divisions are well defined : The Pharynx ( ?) , Oesophagus (Oes) , Crop 

 (Cr), and the proventriculus (Pve). The well developed proven- 

 tricula are the characteristicum of the adults. 



The pharynx is not distinctly defined from the mouth cavity. 



The oesphagus is about as long as the crop and the proventriculus 

 united. It consists of a simple tube, widened distally where it gradu- 

 ally passes over to the crop. 



The strongly widened tube situated apically of the proventriculus 

 may be designated as the crop. 



Proventriculus. — The proventriculus is a highly specialized organ 

 in which the food is prepared before it enters the more delicate ventric- 

 ulus. The characteristic features of the proventriculus are a remarka- 

 ble development of the chitinous intima into folds and teeth and a 

 considerable increase of the size and development of the muscles of 

 this region. On account of the importance of the proventriculus as 

 a taxonomical characteristicum and of the general morphological in- 

 terest of this structure, a more detailed discussion seems to be 

 necessary. 



Lindeman, who was the first investigator of the Scolytid proven- 

 triculus. distinguished two main parts or longitudinal divisions. The 

 anterior part he called the Sack, the posterior, or caudad part, the 

 Kaumagen. Nuesslin and Fuchs followed Lindeman's nomenclature. 

 The Sack (Lindeman) corresponds to the crop (Hopkins) and forms 

 the intermediate part between the oesophagus and the Kaumagen 

 (Lindeman). Hopkins used the term proventriculus for the Kau- 



1 



