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TEXT-BOOK OF ENTOMOLOGY 



The external opening of the spiracles just under the fore wings, is 

 situated in a little plate called by Audouiu the peritrzme. 



In the higher or aculeate Hymenoptera, besides the three segments 

 normally composing the thorax, the basal abdominal segment is 

 during the change from the larva to the pupa transferred to this 

 region, making four segments. This first abdominal is called " the 

 median segment" (Figs. 93-95). In such a case the term alitrunk 



D 



p 



FIG. 93. Transformation of the bumble bee, Bombus. showing the transfer of the 1st abdominal 

 larval segment (<) to the thorax, forming the propodeum of the pupa ( />> and imago ; 11, spiracle of 

 the propodeum. A, larva; <i, head; b, 1st thoracic ; c, 1st abdominal segment. H, semipiipa; 

 ff, antenna; /(, maxilla-; i, 1st; .;', -Jd leg; /', inesoseutum ; f, mesoseutellum ; in, metathorax ; cf, 

 urite (sternite of abdomen) ; c, pleurite ; /, tergite ; o, ovipositor; r, lingua; q, maxilla. 



has been applied to this region, i.e. the thorax, as thus constituted. 

 Latreille wrongly stated that in the Diptera the first abdominal 

 segment also entered into the composition of the thorax; but Brauer 

 has fully disproved that view, as may be seen by an examination of 

 his sketches which we have copied (Fig. 94). 



The sternum is in rare cases subdivided into two halves, as in 

 the nieso- and metathorax of the cockroach ; in Forficula the pro- 



