262 PTILOTA : IMAGO EXTERNAL ANATOMY. 



terms for the upper surface only of the thoracic segments, 

 giving to their under surfaces the names of anti-pert us, 

 medipectus, and postpectus. MacLeay applies the term 

 tergum to the upper surface, and pectus to the lower : thus 

 we have " tergum of the prothorax, pectus of the meso- 

 thorax, &c." Burmeister, with more uniformity and philo- 

 sophic acumen, gives the following series of names : 



Thoracic Segment. Upper Surface. Under Surface. 



1. Prothorax. Pronotum (T 1). Prosternum (T 1). 



2. Mesothorax. Mesonotum (T 2). Mesosternum (T 2). 



3. Metathorax. Metanotum (T 3). Metasternum (T 3). 



This being the most simple system of nomenclature 

 hitherto proposed for these thoracic segments, I shall 

 adopt it, leaving it optional for the reader to regard the 

 segments either as entirely distinct, or as conjointly consti- 

 tuting the thorax, or as divisible into two portions, corre- 

 sponding with the manitrunk and alitrunk of Kirby and 

 Spence. I will only observe, that the blunders of unphi- 

 losophical describers of insects who contented themselves, 

 in many cases, with no more anatomical knowledge than 

 would enable them to distinguish one species from another, 

 and who have, consequently, employed names without know- 

 ing or caring for their precise meaning can be no ground 

 for disputing the existence of organs, still less for asserting, 

 as has inconsiderately been done, that the researches of such 

 men as Lyonnet, Leon Dufour, Chabrier, Herold, Strauss- 

 Durckheim, Savigny, Audouin, and MacLeay, " tend to illus- 

 trate a theory, in itself evidently false, rather than to find 

 out and establish plain and solid truths." 



The complicated machinery requisite for the due perform- 

 ance of the two chief kinds of insect locomotion, namely, 

 leg-movements, including creeping, running, swimming. 

 climbing, as well as prehension, and wing-movements or 

 flying, and likewise the great volume required by the organs 

 of motion themselves, have necessarily produced a great in- 

 crease in the size of the three segments of the body forming 



