THE ECTOPARASITES OF THE RED GROUSE 349 



differences, and seems to consider that a new species might have been described 

 from these specimens. 



Andrew Murray, in his book on " Economic Entomology," l writing of Goniodes 

 tetraonis, says : " This is the insect which sometimes, especially in the bad 

 seasons, does so much harm to the young Grouse when they are feeble and 

 unhealthy." 



It is the commonest of the insects which infest the skin of Grouse, crawling 

 about amongst the base of the feathers and on the vane of the feathers themselves. 

 It occurs more commonly than Nirmus cameratus, which is often associated with 

 it. It is comparatively rare to find a bird free from these " biting-lice," but 

 perhaps 10 per cent, is about a fair estimate of the number of uninfested Grouse. 

 The number on each bird is to some extent an inverse measure of their health. 

 Careful search will discover but two or three on a healthy Grouse, but on a 

 " piner " hundreds may be met with. This is not, however, the case with birds 

 that die quickly of acute disease. 



Goniodes tetraonis is usually found on the smaller feathers, crawling about 

 halfway between their insertion and the tip of their vanes. When disturbed they 

 hurry away into the brushwood of the small feathers, like small deer seeking cover, 

 and they are by no means so easy to catch as one would at first think. They eat 

 the finer barbules of the feathers, which, accumulating in the crop, give the dark 

 curved marking in their rather transparent bodies. On this meagre and arid diet 

 they seem to flourish, actively produce young, and pass through several ecdyses. 



The naked-eye colour of Goniodes is a yellowish brown. Under the micro- 

 scope the body appear? rather transparent, but wherever there is chitin this is of 

 a yellowish to chestnut-brown colour according to the thickness. The crop, which 

 is full of minute fragments of the finest barbules of the feathers, presents a blackish 

 sac-like appearance, running obliquely across the middle line of the abdomen ; a 

 somewhat parallel but much smaller black tube represents possibly the rectum 

 (Fig. 4). In a few cases the oesophagus and crop presented a red appearance, 

 this being probably due to haemoglobin from the blood of the Grouse. The body is, 

 on the whole, flattened especially is this the case with the head and abdomen. 

 The thorax, as Snodgrass 2 points out in Menopon persignatum, appears to be 

 triangular in cross-section. 



The head is shaped somewhat like the semicircular knives used for cutting 



1 Chapman & Hall, London, 1877. 



2 "Occasional Papers of the California Academy of Sciences," vi. p. 145, 1899. 



