342 



PSYCHE. 



[May. 1902 



These can be seen through the semi- 

 transparent mentum and labium, offering 

 an irregular, obovate outline. A short 

 duct from the lower end of each gland 

 leads into a common duct which opens 

 in the oesophageal bone as already de- 

 scribed. The ducts curve over the lower 

 end of the glands and run up their pos- 

 terior surface, to which they are soldered 

 nearly to the top. The line of the ducts 

 together with the lateral outlines, give 

 the glands a three-cornered shape, some- 

 what like that of a butternut. A little 

 triangular cup fits on the summit of each 

 gland, and on it is inserted a suspensory 

 muscle, the upper end of which is 

 attached to the cranium." (Figures of 

 "bone" and ducts are given in Bur- 

 gess's paper and copied in plate LXIV 

 of New Mallophaga II.) 



I have again simply to add that the 

 " oesophageal bone " and its accessory 

 " lingual glands " of the Psocidae, are 

 surely the "oesophageal sclerite " and 

 its accessory glands of the Mallophaga- 



The important thing about this corre- 

 spondence between " forks" and oesopha- 

 geal structures in the two groups is that 

 the same structures do not occur else- 

 where among insects. 



Perhaps the most familiar Psocid form 

 is the degenerate genus Atropos. It is 

 very different from the winged forms ; in 

 fact it is the "link" that connects the 

 winged Psocidae with the Mallophaga. 

 In Atropos as in the Mallophaga there 

 are no traces of wings ; the whole body, 

 head, thorax, and abdomen is flattened 

 exactly as in the Mallophaga; the meso- 



thoracic and meta-thoracic segments are 

 ■fused to form a single segment, one of 

 the characteristic structural conditions 

 of the Mallophaga, while the great devel- 

 opment of the clypeus and the restriction 

 of the mouthparts to the ventral aspect 

 of the head, so characteristic of the bird- 

 lice, is quite as characteristic of this 

 degraded Psocid. So too the peculiar 

 condition of the labrum in the Mallo- 

 phaga lying as it does on the ventral 

 aspect of the produced clypeus finds an 

 identical repetition in Atropos. The man- 

 dibles of Atropos present a really striking 

 similarity with those of the Amblycerous 

 group of the Mallophaga, the details of 

 teeth, condvles, facets and musculation 

 being extraordinary alike. 



The internal anatom)' of the Psocids 

 has yet to be worked out in detail, 

 although Nitzsch, in 1821, described 

 the alimentary canal and the reproduc- 

 tive organs of Clothilla puhatoria (a 

 degraded wingless form much like 

 Atropos). He found the alimentary 

 canal to be very simple, without special 

 crop or proventriculus, and with a simple 

 elongate stomach consisting of a sac-like 

 anterior part and a longer tubular pos- 

 terior part. There are four Malpighian 

 tubules. The intestine is very short, its 

 rectal portion being as long as all the 

 rest of it. The ovaries consist of five 

 egg-tubes on each side ; connected with 

 the oviduct there is a peculiar accessory 

 gland consisting of a sac containing 

 other small sacs each with an elongate 

 efferent duct, the number of these sec- 

 ondaiy sacs varying from one to four 



