50 



misunderstood. Instead of forming a single, simple, rod-like 

 process, this inner lobe is three or four times as long as has 

 been presumed and is two-jointed, the apical joint lying, when 

 the organ is at rest, beside the basal joint, which is attached to 

 the maxilla at the extreme base of the latter ; the basal joint is 

 directed backward and lies almost directly beneath the basal 

 portion of the apical joint. The two portions of the inner lobe 

 which lie, when at rest, behind the base of the maxilla are the 

 parts which have been overlooked ; the cause of the oversight 

 is that they are less corneous~than the distal half of the apical 

 joint, and that they connect with the maxilla almost dii'ectly 

 below the tendinous attachments of the muscles of the head to 

 the inner base of the jaws, with Avhich, from the transparenc}'' 

 and minute size of the creature, they may readily be con- 

 founded in an object mounted for the microscope ; the distal 

 half of the apical joint has therefore been taken for the entire 

 inner lobe. 



This same structure, first seen in Atropos, appears also in 

 Rhyopsocus, recently described by Dr. Hagen from Kerguelen 

 Island, of which he says ^ " the long horny stem straight, bifid 

 on tip, exterior branch [of the bifid tip] a little longer." I have 

 not been able to examine any mounted Psocina, to see whether 

 the inner lobe is similarly constructed in the other branch of 

 the family, but it hardly seems possible that it can be otherwise ; 

 for it is not easy to conceive how a bifid, corneous rod could be 

 used, if simply attached as a process to a maxilla moving at 

 right angles to the longer axis of the process. As a jointed 

 organ, capable of being bent upon itself, it could be thrust sud- 

 denly forward to spear any object with the tines of its micro- 

 scopic fork. It is, however, curious that, Avhen at rest, the two 

 joints are folded so closely together, that in more than twenty 

 mounted specimens which I first examined they Avere in almost 

 precisely the same position, and in no instance was the portion 

 of the apical joint which crossed the maxilla removed outwardly 

 so far as to lie Avholly beyond it. This led me at first to doubt 

 whether the parts I saw behind the maxilla really belonged to 

 this inner lobe, but in every case where the parts were not ob- 



1 Bull. U. S. Nat. Mus., iii, 53. 



