1894.] MICROSCOPICAL JOURNAL. 57 



cover glass on a slide and filling with benzole which is 

 alternately heated and cooled adding fresh benzole to 

 supply the loss from evaporation until the spaces are 

 seen to be entirely filled. Then balsam in benzole is 

 added at the edge of the cover and the mount left to fin- 

 ish. The s[)ecimens in vials or on slides should l)e labeled 

 with at least the name of the host animal and will nat- 

 urally receive the date and name of the collector in addi- 

 tion. The record of dates for s])ecimens in this group 

 have however little importance as regards the life history 

 and development of the insect. 



These parasites are contained in two groujjs, the l*e- 

 diculidse and the Mallopliagida\ 



The first group forms a division of the Hemiptera and 

 has frequently been made a separate suborder {Para.sitd i 

 and placed as the lowest of the Hemiptera. Tiiis how- 

 ever is based only on the simplicity of structure due to 

 degradation and is clearly unwari'anted on any l»asis of 

 [>hilogeny. 



The second group was formerly placed as an aberrant 

 division of the Hemiptera, but is now recognized as hav- 

 ing its affinities with the lower Mandibulate insects and 

 related to the Psccida\ The Pediculida> are found only 

 upon mammals while the Mallophagida* appear upon 

 mammals and also upon birds. The Pediculids are (juite 

 constant as regards the species of animal which they in- 

 fest ; so much so that ordinarily species may be determ- 

 ined by simply knowing the animal horn whicli specimens 

 have been taken, nevertlieless the student will desire to 

 know something of the characters which distinguish the 

 different genera and species. They are mostly soft bod- 

 ied, have simple tubular mouth parts, the antennje are 

 simple, usually of five joints and the legs are frequently 

 modified in different ways and also adapted for clasping, 

 the claws being strong and opposed to prominences upon 

 the tibi?e. Tti some cases there is a special structure for 



