S24 



HYMEXOPTERA 



Fig. 3i7. — Ovipositor of Xeurotenis laevius- 

 culus. (After Adler.) a, a, The ovi- 

 positor partially coiled ; 6, extremity of 

 posterior plate ; c, €, muscles. 



there is a very slender ovipositor, of which only a small part pro- 

 trudes, although the organ is really elongate ; it is drawn into the 



abdomen by means of a peculiar 

 series of structures, the modi- 

 fied terminal segments to which 

 it is attached being folded over 

 into the interior of the body 

 in such a way that the pos- 

 terior part becomes situated 

 anteriorly. In conformity with 

 this arrangement, the oviposi- 

 tor is bent double on itself, 

 the anterior and the middle 

 portions of the borer being 

 carried into the body, leav- 

 ing only a small part projecting beyond the extremity. The 

 Cynipid ovipositor is an instrument of much delicacy, and 

 is capable of a great deal of movement ; it is usually serrate 

 just at the tip, and although it looks so very different from the 

 cutting apparatus of the sawflies (Fig. 344), it seems that it is 

 really composed of pieces similar in their origin to those of the 

 Tenthredinidae. 



The wings frequently bear fine hairs ; the paucity of nerv- 

 ures and the absence of the " stigma " are of importance in 

 the definition of the family. The most important of the cells is 

 one called the radial cell, situate just beyond the middle of the 

 front part of the wing. 



We cannot enter into a coiisideration of the classification of 

 the family, as authorities are not agreed on the subject.^ As 

 regards their habits Cynipidae are, however, of three different 

 kinds: (1) the true gall-flies, or Psenides, which lay an egg or 

 eggs in the tissues of a growing plant, in the interior of which 

 the larva lives after it is hatched ; this mode of life may or 

 may not, according to the species, be accompanied by formation 

 of a peculiar growth called a gall: (2) Inquilines,^ or guest-flies; 



^ See Cameron, Srit. Phyt. Hym. iii. Kay See. 1890, p. 152. 



'^ The term inquiliiie is applied in entomology to a great variety of conditions 

 covered by the Latin word "inquilinus" (incolinus), signifying a tenant or dweller 

 in another's property. The term parasite is used in a still wider and vaguer sense, 

 being in fact applied to a large number of cases, in many of which w-e do not at 

 present understand the exact relations between the two parties concerned. This 



