520 



HYMENOPTERA 



of the Order. Although it includes many of the most interest- 

 ing and important of Insects, its classification 

 is but little advanced, for a great many of 

 the forms are still rare or unknown. Three 

 series may be adopted for the purposes of 

 nomenclature. 



1. Parasitica. Trochanters of two pieces, 

 female with an ovipositor. 



2. Tubulifera. Trochanters undivided ; ab- 

 domen consisting of only three, four, or five 

 visible segments. 



3. Aculeata. Trochanters undivided; abdo- 

 men consisting of six or seven visible segments ; 

 female furnished with a retractile sting. 



In the absence of any clear distinction 

 FIG. 345. Divided (di- between sting and ovipositor, these groups are 



trochous)trochanter . , , , . , , 



of an ichneumon: merely conventional. Ihe character furnished 

 , coxa ; b, the two by faQ trochanters is unfortunately subject to 



divisions of the tro- . . . . 



chanter; c, femur, some exceptions, there being a lew parasitic 

 (For monotrochous formg in w hi c h t h e trochanters are not divided, 



trochanter see Fig. 



335, A, c.) and a few aculeates in which the reverse 



is more or less distinctly the case ; moreover, 

 the division, when it exists, is in some cases obscure, and the two 

 pieces are of unequal size. Ratzeburg calls the upper division, 

 which is frequently much larger than the other, the trochanter, 

 and the lower division the apophysis. There is much reason 

 for believing that the apophysis is really merely a secondary 

 division of the femur. The Tubulifera are a comparatively small 

 group, and will probably be merged in one of the other two, 

 when the anatomy and morphology of the abdomen have been 

 more thoroughly elucidated. 



Hymenoptera Parasitica or Terebrantia. 



This is one of the most extensive divisions of the class 

 Insecta. There can be little doubt that it contains 200,000 

 species, and possibly the number may be very much greater than 

 this. It is, however, one of the most neglected of the great 

 groups of Insects, though it is perhaps of greater economic 

 importance to mankind than any other. 



