122 Proccr(Un!/s of liKJiajia Academy of Science. 



will give excellent preparations, which are strilvin^ly clear, if no air or 

 water remain in the insect. 



Another methofl. simpler and decidedly quicker is to mount the louse 

 directly from absolute alcohol into Euparal. Euparal as recommended 

 very highly by Lee. is a mounting medium whose index of refraction varies 

 to such an extent as compared to that of the cleared louse, that it allows 

 very minute structures such as pustulated hairs to be seen very distinctly 

 and advantageously. Another advantage in this technique lies in the fact 

 that xylol is not needed as a final clearing agent and less shrinkage results 

 in the insect. Moreover, the expense of xylol is entirely eliminated. 



Such mounts will allow the internal anatomy to be seen in part. If the 

 internal anatimiy is not desired jiarticnlarly a still clearer specimen can 

 be obtained. 



If the louse be placed into caustic potash or caustic soda previous to the 

 final steps in deh.vdration. all internal structures that cause some opacity 

 will be dissolved. It usuall.v requires from to 12 hours to completely 

 clear the specimens after which they should be well washed in water before 

 the final dehydration is undertaken or certain colloidal precipitates will 

 form later. Moreover, the procedure .iust described will enable one to 

 straighten out all legs, which had been drawn under the body during killing, 

 whether directly by alcohol or hot water. They become quite soft in the 

 potash and are somewhat easily handled. 



Some precautions are necessary in the final mounting into Euparal in 

 order that the air ma.v not enter the legs and abdomen of the louse, and 

 cause it to become entirely opaque. To overcome this requires care not to 

 expose the specimen to air in removal from the absolute alcohol to the 

 mounting medium. If. after some time, siich mounts in Euparal develop 

 peculiar polygonal crystals, they can be removed by gently heating the slide 

 over a flame or in an oven. These crystals are camphor which has crys- 

 tallized out and which was one of the solvents of the resin used in making 

 Euparal. i. e.. — Gum Sandarac. 



The species-determining characters in lice are many and varied. In the 

 main, they constitute the greatest ditficxdty in the study of lice and require 

 considerable attention. 



The nomenclature of anatomical parts of lice in this pai»er is that followed 

 by Kellogg in his New Mallophaga I, (1896). 



The head of a louse may be said to consist of two main parts. The front 

 which includes the clypeus. and the large swollen hindpart or occiput. The 

 fi-ont and occipital regions are usually separated l)y a groove or fossa in 

 which are situated the antennae. This is the antennal fossa. The lateral 

 margin of this region is called the temporal margin and the posterior 

 margin ad.ioiniug and touching the prothorax is the occipital margin. With- 

 in this swollen occipital region are found bands running from the base of 

 the occipital margin to the inner end of the antennal fossa. These are the 

 occipital bands. Those bands running forward, well into the front and 

 arising at the antennal fossa are the antennal bands. The broad colored, 

 chitinized plate between the antennal bands, is the signature. In some gen- 

 era, as Docophorus and Nirmus, there arise at the lateral margin, and ad- 

 joining the antennal fosa, certain large movable spine-shaped structures. 



