THE ECTOPARASITES OF THE RED GROUSE 353 



the pro thoracic legs do not move synchronously with either of the others or with each 

 other. One often moves backward as the other moves forward, and he holds that 

 they serve to guide the body. He thinks they serve to pull the body up the feather, 

 the prothoracic legs pulling whilst the other legs push, like a man climbing a rope. 



VII. The Mesothoracic Legs. These are larger than 'the preceding, and are 

 directed backwards ; their bases are further apart. The details are shown Mesothor- 

 in Fig. II. All the legs end in claws and bear a well-marked pulvillus. acic Iegs- 



VIII. The Metathoracic Legs. These are still larger and, like the preceding, are 

 directed backwards ; the sternum between their bases is rather wider. The right 

 and left mesothoracic legs move forward simultaneously and backward Metathor- 

 simultaneously, and so do the right and left metathoracic legs ; but when acicle s s - 

 the mesothoracic legs move forward the metathoracic legs move backwards, and 

 vice versd. 



In their general structure there is little beyond size in which the legs differ. 

 Each consists of a coxa firmly applied to the ventral surface of the thorax ; it is a 

 broad, short piece, wide distally. The second article is a small trochanter which 

 joins the hinder end of the wide coxa and seems to be almost part of the femur, but 

 there is a marked thinning of the cuticle between it and the femur and a clear joint. 

 The femur with the trochanter and the next article or tibia are of about equal 

 length, but the tibia is not so stout ; distally it bears a pair of stout bristles, hardly 

 moveable, against which the tarsal claws work. There are other bristles on the tibia r 

 and numerous hairs on all the articles. The tibia bears a single-jointed tarsus which 

 carries a pair of very mobile claws. These claws are constantly being depressed, 

 usually one at a time, and rub against the tibial bristles. The tarsus always carries 

 numerous knobs, and between the base of the claws a pulvillus may be seen ; this 

 in some cases is retracted. 



The female has no external organs of reproduction, but on the seventh segment 

 of the male there are situated ventrally a couple of complicated gonapophyses which, 

 presumably are modified abdominal appendages. 



The tracheal system of Goniodes opens on the exterior by seven pairs of stigmata. 

 There may possibly have been more, but we could not detect them. The most 

 anterior is the largest ; it is situated close behind the first pair of legs, and Respiratory 

 is very difficult to see. Snodgrass l has described one in a similar position systl 

 in Menopon titan. From it a trachea passes inwards and gives off a twig to 

 the second leg. 



1 "Occasional Papers of the California Academy of Sciences," vi., 1899. 

 VOL. I. Z 



