554 



HYMENOPTERA 



have an ovipositor three or four inches in length, and are parasitic 

 on species of the family Siricidae, which, as we have previously 

 described, live in solid wood. In order therefore to deposit 

 the egg in a suitable place, the wood must be pierced by the 

 Ichneumon. The ovipositor is not only of extreme length, but is 

 also furnished with serrations on its apical part, so that it forms a 

 very effective boring apparatus. It is brought into use by being 

 bent on itself over the back of the Insect (Fig. 362), so as to bring 

 the tip vertically down on to the wood, through which it is then 

 forced by a series of efforts ; the sheaths do not enter the wood. 

 The egg is laid anywhere in the burrow of the Swex ; the young 

 larva seeks its prey, and lives on it as an external parasite (Fig. 

 342, D). Erne, however, states^ that the young larva of Rhyssa 

 persuasbria enters its victim, and remains within the latter till its 



death occurs. This happens 

 when the young Ehyssa is 

 two or three lines in length, 

 and it then makes its exit from 

 the interior of the body and 

 gradually eats it up. Should 

 the larva it has attacked be of 

 large size, it of itself affords 

 sufficient food for the comple- 

 tion of the growth of the 

 Bhyssa. Should the Rhyssa y 

 however, have attacked a small 

 larva, this does not furnish it 

 with sufficient food, and it con- 

 sequently dies without seeking 

 another larva. Erne says, 

 indeed, that it will not eat 

 another if offered to it, so that 

 in order to rear the Rhyssa in captivity, the victim it has first 

 attacked must always be given to it. The same observer states 

 that the Rhyssa larva is sometimes transported by the Sirex 

 deep into the wood, so that when it has completed its metamor- 

 phoses the Ichneumon-fly may find itself buried in solid wood to 

 a depth of about two inches. In that case it excavates the wood 

 with its mandibles, and should it fail to gain the exterior after 



^ Mitt, schweizer. cnt. Ges. iv. 1876, p. 518. 



Fig. 362. Thalessa lunator. 

 (After Riley.) 



Oviposition. 



