ISLE oj* Wight disease in hive bees — acarine disease. 76& 



pure nelle femmine, normali, conformate come quelle del secondo e terzo pajo, 

 coUa differenza che hanno un' unghia sola. Zampe del quarto pajo nel maschio 

 robuste, constituenti insieme unachela, terminate da un' unghia robusta. Epimeri 

 del terzo e quarto pajo nel maschio assai lunghi e forti e convergenti insieme 

 verso I'avanti. Scudo dorsale diviso in segmenti. Animali viventi su piante." 



The adult female of the species to be described conforms well to the generic 

 characters given above, and cannot, in my opinion, be separated from the genus 

 Tarsonemus. The only morphological character upon which such a separation 

 could be based is the conformation of the fourth pair of legs, and possibly the 

 absence of pseudostigmata (not included in the original generic description). The 

 male is undoubtedly more specialised in the fourth leg characters, but to con- 

 stitute a new genus upon this fact, or upon the parasitic habit with which this 

 specialised feature appears associated, seems to me inadmissible, at any rate in 

 the present state of our knowledge. 



A distinctive feature of the genus Tarsonemus is the fourth pair of legs, 

 which in the female are slender, terminate in two hairs, and are devoid of 

 claws. In the male, in the gall-inhabiting and free-living species, the last pair 

 of legs is robust and terminates in a claw-like segment, usually incurved and 

 frequently strongly developed. In some of the species recorded as endoparasitic, 

 these characters in the male appear less well marked, and in the main show a 

 reduction in size of this pair of appendages. In the species to be described the 

 hind legs in both sexes present, especially in the male, features which I regard 

 as related to the parasitic mode of life and restricted habitat of the insect's 

 tracheal system. 



Tarsonemus woodi, n. sp. 



I propose to designate this species, which is parasitic in the anterior thoracic 

 tracheal system of the hive bee, Apis mellifica, and which does not appear to 

 have been described before, by the name of Tarsonemus woodi, n. sp. The adult 

 ovigerous female measures from '14 to '19 mm. in length, the male about "11 to 

 '15 mm. (fig. l). Viewed with reflected light, these mites are more or less bean- 

 shaped in form, greyish in colour, and scantily bedecked with hairs. When removed 

 from the trachese of the bee they progress slowly upon glass, but when seen within 

 the tube, although continued observation has not revealed much progression, a good 

 deal of active and vigorous leg movement may be observed. 



OviGBROTJS Female. — Seen from 'above, the body presents a somewhat oval 

 form, broadest in the neighbourhood of the second pair of legs. The following are 

 typical dimensions for a fully grown adult : — 



Total length from tip of gnathosoma to hinder end of body, '19 mm. 



Total length from tip of gnathosoma to tip of longest hair of fourth pair 



of legs, '25 nim. 

 TKANS. ROY. SOC. EDIN., VOL. LII, PART IV (NO. 29). 119 



