340 



PSYCHE 



[May, !go2 



mate identity is, of course, not deter- 

 minable by arbitrary convention, nor, in 

 the present state of zoological science, by 

 quantitative measure, but its recognition 

 is in most cases obvious to all naturalists, 

 and the power to recognize parallelism 

 when existing, and to recognize identity 

 due to common origin and descent when 

 existing is simply one of the required 

 qualifications of the competent systematic 

 zoologists. In my belief the Mallophaga 

 and Psocidae possess in common certain 

 peculiar and characteristic structural fea- 

 tures (coupled with corresponding physi- 

 ological features) whose practical iden- 

 tity must be ascribed to community of 

 origin and which thus reveal a commu- 

 nity of descent on the part of the insects 

 themselves. 



In my paper New Mallophaga II 

 previously referred to, are described and 

 illustrated in detail the mouthparts of 

 four Mallophagous genera (pp. 431-457 

 plates LX-LXII). Three of these 

 genera thus described, and ten other 

 genera examined, although not described 

 in detail, are found to possess a well- 

 developed peculiar pharyngeal or oeso- 

 phageal sclerite characteristically con- 

 stant in position and • shape, and of 

 important use in the manipulation of 

 the dry food (bitten off parts of feathers) 

 of the insects. (In four of these genera 

 there appear to be species lacking the 

 sclerite — or, at least, having it in such 

 weakly chitinized condition as to make 

 it invisible when the undissected head of 

 the specimen is examined.) In five 

 Mallophagous genera this sclerite is ab- 



sent. In the four remaining known 

 genera of the order no specimens are at 

 hand. This peculiar sclerite is a thick- 

 ening of the chitinous intima of the pha- 

 rynx, and appears as a bonnet-shaped 

 sclerite lying on the ventral wall of the 

 pharynx, with hollow part upward, with 

 median groove closed behind, projecting 

 processes at the interior angles, and a 

 pair of long slender "bonnet string" 

 pieces, which project dorsally and pass 

 on either side of the pharynx, or oeso- 

 phagus, upward and around it, and attach 

 by their ends to the dorsal wall of the 

 head. Opening into the median groove 

 from its ventral side is a small duct, 

 which, followed to its source, is seen to 

 come from the union of a pair of ducts, 

 each one of which comes from an oval 

 gland lying ventral to the sclerite, and 

 fitting into a concavity on the anterior 

 end of a weakly chitinized, pedicel-like 

 structure, which projects backward and 

 is attached by a foot-shaped expansion 

 to a large, strong muscle. (Figures of 

 this oesophageal sclerite and glands are 

 given on plate LXII in New Mallophaga, 

 II.) 



Apart from this peculiar addition to 

 the usual biting insect mouth, two of the 

 four genera of Mallophaga whose mouth- 

 parts were carefully studied were found 

 to possess certain peculiar "forks" in the 

 mouth, which by dissection are seen to 

 be very small chitinous rods lying inside 

 of the mouth above the labium whose 

 posterior ends attach to the ventral wall 

 of the head by muscles, and whose 

 anterior ends are strongly forked or 



I 



