fi70 



MR. R. K. ('1;M.MJ.NG,S OX LICK 



The Mouth-parts In the Genus Ibidoecus. (Text-fig. 20.) 



It is necessary to revert once more to the subject of the 

 jharyngeal sclerite (or lyriform organ) referred to on p. 273 of 

 Fart I. and on p. C56 of the present instalment, inasmuch as 

 within this single genus Ibidcectis may be found species with 

 these organs modified (as they occur in scattered instances 

 throughout the Order), at least one species in which the parts 

 are normal as in most Mallophaga, and in the species /. flavus a 

 valuable intei'mediate stage. 



Text-figiure 20 



Ih idaecus flaims. Isopogometnc apparatus. X 290. 



'G.. "gland." AC. anterior cornu, PC. posterior corn u, and N. "nucleus" 

 of the lyriform organ. 



This isopogometric appaiatus, as Armenante (10) called it (on 

 the theoiy that it was a contrivance for measuring the barbules 

 into equal lengths for cutting) *, was supposed by Snodgrass (1) 

 to be absent in some Mallophaga, such as Lcemohothrion, An- 

 cistrona, Nltzschia, Physostotniim, Trinoton, and others. In 



* The fact that a similar apparatus is present in the Psocidse, which do not feed 

 on feathers, does not necessarih' disprove Armenante's theory, as its present function 

 majf he a new one, involving the adaptation of old parts. It is certainly difficult to 

 believe tliat the so-called '"g-laiids" (now apparently wholly chitiuous) were not once 



ilauilular, w liich they may still be i'n pa-rt. 



