HYMEN OPT ERA 



CHAP. 



connected that it is not easy to count them. The abdomen is, 

 in the great majority, of very peculiar construction, and allows 

 the Insect to curl it completely under the anterior parts, so as to 

 roll up into a little ball ; the dorsal plates are very strongly 

 arched, and seen from beneath form a free edge, while the ventral 

 plates are of less hard consistence, and are connected with the 

 dorsal plates at some distance from the free edge, so that the 

 abdomen appears concave beneath. In the anomalous genus 



Cleptes the abdomen 

 is, however, similar 

 in form to that of 

 the Aculeate Hymen- 

 optera, and has four 

 or five visible seg- 

 ments, instead of the 

 three or four that 

 are all that can be 

 seen in the normal 

 Chrysididae. The 



larvae of the Euby- 

 tties have the same 



.friG. 1. Chrysis ignita, 9- England. 



number of segments 



as other Hymenoptera Petiolata. The difference in this re- 

 spect of the perfect Chrysididae from other Petiolata is due 

 to a greater number of the terminal segments being indrawn 

 so as to form the tube, or telescope-like structure from which 

 the series obtains its name. This tube is shown partially 

 extruded in Fig. 1 ; when fully thrust out it is seen to be 

 segmented, and three or four segments may be distinguished. 

 The ovipositor proper is concealed within this tube ; it appears 

 to be of the nature of an imperfect sting ; there being a very 

 sharply pointed style, and a pair of enveloping sheaths ; the style 

 really consists of a trough-like plate and two tine rods or spiculae. 

 There are no poison glands, except in Cleptes, which form appears 

 to come very near to the Aculeate series. Some of the Chrysi- 

 didae on occasions use the ovipositor as a sting, though it is only 

 capable of inflicting a very minute and almost innocuous wound. 

 Although none of the Ptuby-flies attain a large size, they are 

 usually very conspicuous on account of their gaudy or brilliant 

 colours. They are amongst the most restless and rapid of Insects ; 



