460 CALIFORNIA ACADEMY OF SCIENCES. 



they are very small, fine, chitinous rods lying inside of 

 the mouth above the labium, whose posterior ends are at- 

 tached to the ventral wall of the head by muscles and 

 whose anterior ends are shortly forked or bifurcated, and 

 project through the lining of the ventral wall of the mouth, 

 thus lying free and uncovered in the mouth cavity. 

 Although not observed in the other two genera of Mallo- 

 phaga dissected, it is not at all certain that they are not 

 present, their extreme minuteness and delicacy making 

 their discovery a matter of difficulty. 



The oesophageal sclerite and glands are also structures 

 of extreme interest from their probable identity with 

 similar structures in the Psocidae. They do not appear to 

 be present in all the Mallophagous genera ; but I have ob- 

 served them in a majority of the genera, viz., Docophorus, 

 JVtrmus, Lipeurus, Eurymetopus, Goniodes, Goniocotcs, 

 Giebelia, Oncophorus, Trichodectes, Colpocephalum, and 

 Menopon; also in Piaget's figures of Akidoproctus the 

 sclerite is indicated. I have found the sclerite and glands 

 absent in Ancistrona, Nitzschia, Trinoton,Lcemobothriiim , 

 and Physostomnm. It will be noted that the sclerite and 

 glands are present in all Ischnocera examined, and in two of 

 the Amblycerous genera ; while in a number of other Am- 

 blycerous genera the structures are wanting. In Lcemo- 

 bothrium, where the sclerite is wanting, there is a pair 

 of glands in the labium, evidently quite distinct from the 

 oesophageal glands so far referred to. This oesophageal 

 sclerite is a thickening of the chitinous intima of the 

 pharynx, and appears as a bonnet-shaped sclerite lying 

 on the ventral wall of the pharynx, with hollow part up- 

 ward, with median groove closed behind, projecting pro- 

 cesses at the anterior angles, and a pair of long slender 

 " bonnet string " pieces, which project dorsally and pass 

 on either side of the pharynx, or oesophagus, upward and 



