138 PIMPLINE ICHNEUMONIDAE 



and polished. On each side of the third segment is a small yellowish-white 

 spot: similar spots are found on the remaining segments, increasing in size 

 up to the fifth, after which they decrease. 

 $ Unknown. 



M. nitida may be distinguished from the rest of the Megar- 

 hyssae by means of its dark abdomen with the yellowish-white 

 markings. 



In all probability M. nitida is the male form of M. humida as 

 previously stated. 



Habits of Megarhyssa 



The following extracts are taken from an article by C. V, 

 Riley,'' because he gives the best description of the habits of 

 Megarhyssa. 



" . . . In preparing for the act (oviposition) the position 

 is generally longitudinal or in a line with the axis of the trunk or 

 branch, the head either up or down. With the abdomen raised 

 in the air the ovipositor is taken and managed with the hind legs, 

 and the tip guided by the front tarsi. The two outer sheaths 

 are used as props and do not enter the wood with the ovipositor 

 proper. They are generally crossed — a position which gives 

 additional strength and securit}^ to them. Now, by a movement 

 from side to side, and by arching the abdomen and bearing upon 

 the ovipositor she gradually forces this back through the tip 

 of the abdomen into a membrane which issues from between 

 the sixth and seventh joints dorsally. There is a wonderful 

 muscular power in the anal joints, and the ovipositor is forced 

 back until it forms a perfect coil, so that when the abdomen is 

 stretched in a straight line to its utmost the ovipositor within 

 the membrane makes a circle almost as large as a quarter of a 

 dollar, the anal joint having made a three-fourths turn within 

 the membrane. In this manner the ovipositor under the venter 

 has been sufficiently shortened to bring its tip against the bark. 

 During this operation, however, the outer sheaths, which have 

 not followed the ovipositor within the menibrane, have been 

 obliged to make a more or less irregular coil opposite to and in 

 front of the membrane on the ventral side. Now commences 

 the operation of boring, and with the wonderful muscular power 

 in the anal joint and the elasticity of the membrane, the insertion 

 of the ovipositor goes on quite steadily if the wood be in the 



» Insect Life, i, 1888-89, p. 168. 



