Mr. Westwood on Th;ysa7mra. 89 



XX. Thysanuree Hibernicae, or Descriptions of such Species 

 of Spring-tailed Insects (Podvira and Lepisma, Linn.,) as 

 have been observed in Ireland ; by R. Templeton, Esq., 

 R.A., Corj'. 3Iember of the Natural History Society of 

 Belfast : with Introductory Observations upon the Order, 

 by J. O. Westwood, F.L.S. Sfc. 



[Read June 2, and July 7, 1834.] 



Introductory Observations upon the Thysanura, by J. O. Westwood. 



My friend Robert Templeton, Esq., previously to his departure from 

 England, placed in my hands, for the purpose of its being submitted 

 to the Entomological Society, the following paper, containing de- 

 scriptions of various species of Thysanurous insects which he had 

 obseiTed in Ireland, accompanied by numerous figures, allowing me 

 to make such additional remarks thereon as appeared serviceable by 

 way of introduction. 



If we look at the Thysanura merely as an order of animals whose 

 characters and distinctive peculiarities have hitherto been greatly 

 neglected, the attempt to investigate their structure and specific dif- 

 ferences could not fail to meet with approval ; but there are other 

 circumstances which render the group of insects in question more 

 especially worthy of attention. Firstly, from the rank which they 

 hold amongst annulose beings, being one of those qnastiones vexatcB 

 which it is most desirable should be set at rest, and which it is na- 

 tural to suppose can only be done by a series of minute investiga- 

 tions : thus, whilst Latreille and Leach consider these animals as 

 true insects, Mr. MacLeay removes them far asunder, and places 

 them with the Centipedes, Worms, and Lice in his class Ametabola. 



In the next place, these insects offer a very valuable field of in- 

 quiry from the great modification which the various parts of the 

 mouth undergo in the different groups, and which, when thoroughly 

 investigated, may perhaps lead to the solution of those interesting 

 questions respecting the real analogies of the parts of the mouth 

 amongst the Myriapoda, Arachnida, and Crustacea, respecting which 

 at present scarcely any two entomologists are agreed. 



In some of these animals we find a development of the trophi as 

 great as in some of the most perfect of mandibulated insects ; whilst 

 in others the mouth is so obscurely organized that neither Latreille 

 nor Savigny has been able to trace its formation. 



