232 The Ruffed Grouse 



New York study in most years, but did reach a high incidence from 

 1935 to 1937. From an occasional case in the years up to 1934, the 

 incidence rose to twenty per cent in 1935 and to forty-nine per cent 

 in 1936. Then the rate declined to thirty-four per cent in 1937 and 

 to unimportant numbers thereafter, with no cases at all recorded 

 from 1940 to 1942. In the chicks, it is not common. Only in 1935, 

 when six cases were found in one himdred and twenty-two speci- 

 mens, did it make its appearance in more than a single bird. 



Except for these New York and New England records, the only 

 other record is a single bird from Michigan ( Fisher, 1939 ) . It is an- 

 other one of the parasites having a limited range and is not normally 

 a serious threat to its host. 



Oxyspirura petrowi (Skrjabin, 1929). An eyeworm that is found 

 mider the nictitating membrane, this parasite has been reported 

 only from Michigan (Fisher, 1939). Here it seems to be a rather 

 prevalent and possibly serious pest. In the three years, 1934 to 1936, 

 the incidence in ruffed grouse examined was twenty-eight, twenty- 

 two and five-tenths and fifteen per cent respectively. "As many as 

 seventeen of these worms have been taken from one eye, and a 

 number of birds developed marked cases of conjunctivitis" ( op. cit. ) . 

 Another species of eyeworm, Oxyspirura mansoni ( Cobbold, 1879 ) , 

 Ransom, 1904, was found in three out of one hundred and fifty-five 

 grouse examined by Boughton (1937), there being one worm found 

 in each case. No significance was attached to their presence. 



Microfilaria. These blood parasites have been found in a number 

 of grouse, both old and young, by the New York study ( N. Y. S. Cons. 

 Dept. Ann. Reports, 1933-39). Their numbers are not significant and 

 the incidence only reached eleven per cent one year (1936), seven 

 per cent in 1933 and 1934, and less in other years. Only two cases 

 were found in the chicks. Clarke (1936) reports one occurrence of 

 these parasites in a ruffed grouse from Ontario. None of these in- 

 stances indicated any serious pathological trouble. 



Physaloptera larvae (Rudolphi, 1819). These larval nematodes 

 have been reported by Boughton (1937) from Minnesota and Wis- 

 consin grouse. They are described as, ". . . two to three millimeters 

 long . . . encysted near the surface of the muscles of the breast 

 and in the muscles of the legs. The cysts themselves usually were 



