Thorax of Hymenopterous Insects. 29 



which part Mr. Curtis invariably terms the prothorax. Upon the general 

 formation of the truncus, or, as it is usually called, the thorax of the 

 Hymenoptera, it is not my purpose at present to enlarge, further than to 

 state its primary division into the manitrunk and alitrunk ; I shall there- 

 fore refer the student to Kirby and Spence's Introduction, Vol. III. p. 529. 

 Those authors have satisfactorily shewn that the said anterior conspicuous 

 part, or collar, is a portion of the alitrunk, being attached to the meso- 

 thorax, (a portion of the alitrunk,) to w^hich collar there is no analogous 

 part in the Coleoptera; in the latter order, the true prothorax (or, as it 

 is there generally termed, the thorax,) which is the upper surface of the 

 manitrunk, is very large ; but in the H5mienoptera, the whole manitrunk, 

 including its upper surface or prothorax and under surface or antepectus, 

 becomes diminished, and is generally hidden by the collar, only becoming 

 conspicuous when the upper surface is elongated into a neck as in 

 Xyphydria, or more slightly as in Cheiropachus. 



Explanation of the Plate. 



Fig. 1. Cleonymus depressus $ magnified. 



A. to F. details of ditto, all more or less magnified. 



A. Front view of the head. 



B. Antennse seen from the outside, or from the tip of the 



wino; on the same side as the antenna fi2;ured. 



C. The three terminal joints of the antennae seen from above. 



D. Ditto, seen from within, or from the tip of the other 



antenna. 



E. Under side of the anterior part of the truncus with the 



head removed. 



a. Point of attachment of the head. 



b. b. Deflexed margins of the collar. 



c. c. The antepectus longitudinally divided by a deep groove. 



d. d. The coxEe of the fore legs. 



F. A fore leg. 



G. Under view of the abdomen. 



a. The peduncle. 



b. The first true ventral segment. 



