148 



Avounds of elm and chestnut trees. The other hosts of this parasite 

 are Rhyphtis fenestralis, Scop., Mycetobia pallipes, Meig., Anlacogaster 

 riifitarsis, Meig., larvae of Eristalids, Systeiius adpropinqttans, Loew, 

 Phaonia cincta, Zett., and the T}'roglyphid, Hericia hericia, Robin. 



Buxton (P. A.) . The External Anatomy of the Sar copies of the Horse. — 



Parasitologv,Ca}iibyidge, xiii, no. 2, June 1921, pD. 114-145, 1 plate, 

 22 figs. 



As a result of the suggestion made by Warburton [R. A.E., B, viii, 

 '219] the anatomy of the various stages of Sarcoptes scahiei equi are here 

 described as accurately as possible. A key for distinguishing the larva, 

 nymph, and male and female adult, is given. 



Buxton (P. A.). On the Sarcoptes of Man. — Parasitology, Cambridge, 

 xiii, no. 2, June 1921, pp. 146-151, 9 tigs. 



A comparison is drawn between the anatomy of Sarcoptes scahiei 

 Jiominis, Hering, and S. scabiei equi [see preceding paper]. The species 

 known as Sarcoptes scabiei-crustosae, Fiirst., can only be distinguished 

 from typical S. scabiei by characters that require an oil-immersion 

 lens and micrometer for their appreciation ; it must therefore be 

 relegated to varietal rank, the name being Sarcoptes scabiei scabiei- 

 crustosae, Furst. The minuteness of the morphological differences 

 between the species and variety is urged in opposition to the view held 

 that S. scabiei hominis and 5. scabiei scabiei-crustosae are distinct 

 organisms producing essentially different diseases. Were the mite 

 causing Norwegian crusted scabies really distinct from 5. scabiei 

 Jiominis it would probably have become extinct, as the disease is very 

 rare. The need for further investigations on this subject is indicated. 



HiNDLE (E.). Notes on Rickettsia. — Parasitology, Cambridge, xiii, 

 no. 2, June 1921, pp. 152-159. 



The results obtained from the examination of lice completely agree 

 with those already recorded [R.A.E., B, vi, 237; ix, 137]. It is 

 suggested that the positive results obtained by Continental observers 

 may be due to the prevalence of typhus and trench fever or to the 

 existence in the alimentary canal of the louse of a Rickettsia that 

 is non-pathogenic to man. Rickettsia were unquestionably very occas- 

 ionally found in lice that had never fed on any one infected with either 

 trench fever or typhus. The relation between R. quintana and 

 R. pediculi may be an instance of a non-pathogenic Rickettsia having 

 acquired the capacity of living in the blood of man and producing the 

 pathogenic variety R. quintana. In the case of the latter the insect 

 host merely furnishes a living culture tube in which the organisms grow 

 and multiply without passing through any cyclical changes such as take 

 place in the case of Protozoa. 



R. melophagi, isolated from Melophagus ovinus, was found in the 

 young offspring of infected Melophagus, audit seems probable that this 

 infection is hereditary. It was also frequently associated withCrithidia 

 melophagi. Other species dealt with are R. trichodectae, sp. n., from 

 Trichodectes pilosus from the horse, and R. linognathi, sp. n., from the 

 alimentary canal of the goat louse, Linognathus stenopsis. 



As a result of various observations these organisms have been found 

 to occur at least in two insects, Trichodectes sp. and Psocus sp., that 

 do not feed on blood ; it is therefore probable that Rickettsia represent 



