Spathegaster tricolor. 27 



alike. Thus for example Neiiroteriis fiimipennis and 

 Spathegaster tricolor resemble each other so much in 

 size and colouring, that from a superficial examination 

 they might easily be confounded ; but if we take into 

 consideration their whole structure, the form of the 

 abdomen, the length and shape of the wings, and 

 lastly the ovipositor, the difference between the two 

 generations is found to be sharply defined. 



I will return hereafter to the consideration of the 

 interesting variations in the ovipositor, on account of 

 the importance of that organ. The principal forms 

 exhibited in the illustrations (Plate III) are ac- 

 curately drawn from photographs, so that the various 

 details will be found given in their proper relative 

 proportion. 



As the two generations, just described as species of 

 Neuroterus and Spathegaster^ belong to the same insect, 

 I felt strongly inclined to drop the usual practice of 

 designating them as of two genera ; but I have retained 

 these names, for the present at least, in order to avoid 

 confusion. 



In the earlier descriptions of these two genera the 

 number of joints in the palpi were used as distinctions 

 between Neuroterus and Spathegaster. In Neuroterus 

 the maxillary palpi were said to be four-jointed and 

 the labial palpi two-jointed : and in Spathegaster they 

 were said to be respectively five and three-jointed. 

 But a closer examination of these forms has convinced 

 me that the maxillary palpi have invariably four, and 

 the labial palpi always two joints. 



