Clare Island Survey. 



32 

 APTERYGOTA. 



By GEOEGE H. CABPENTEE, B.Sc, 

 Professor of Zoology in the Eoyal College of Science, Dublin, 



Plate I. 



Eead June 23. Published August 2, 1913. 



The Apterygota collected on Clare Island comprise two species of Thysanura 

 (Bristle-tails) and eighteen of Collenibola (Springtails). My own field-work 

 on Clare Island was restricted to a short week in July, 1911 ; but several of 

 my colleagues, whose names are given below, detected and secured valuable 

 specimens at other times ; for this help I am sincerely grateful. The list 

 might doubtless be extended by research during the colder months of the 

 year ; nearly all the specimens enumerated were found in the summer. 



These lowly insects — primitively wingless, as they are believed to be by 

 most entomologists — are of much interest to the morphologist, and also to 

 the student of geographical distribution. Being without the power of flight, 

 they cannot cross sea-channels unless they be accidentally carried by 

 birds, &c, and a knowledge of their range seems therefore of special value 

 in any endeavour to trace the paths of immigration by which various faunas 

 have reached the districts which they now inhabit. 



It is somewhat disappointing to find that the majority of the Clare Island 

 Apterygota are common and widespread Irish species. The insects of this 

 group inhabiting the island represent, on the whole, an attenuated remnant 

 of forms dominant on the mainland. Yet one of the Springtails — Folsomia 

 iv-oculata (Tullberg)— is one of the least-known members of the Britannic 

 fauna, and has not hitherto been recognized in Ireland. Among the 

 Thysanura, the careful scrutiny given to every Clare Island specimen has 

 yielded the unexpected result that two shore-haunting species — closely 

 similar in appearance, but definitely separable structurally — have been for 

 many years past included under the name Pctrobius (or Machilis) maritimus 

 Leach. The Clare Island Petrobius is that commonly found around the Irish 

 coasts. The characters by which it may be distinguished from its scarcer 

 relation — so far found only in Co. Dublin — are discussed below. 



K. I. A. 1'KOC, VOL. XXXI. A 32 



