July. 1M91. ! 181 



commou origin, thc}'^ probably act simultaneously. The ovipositor is 

 furnished besides with its own pair of proper retractors that withdraw 

 it within the sheath. They take their origin from the points of the 

 outer rods, and each is inserted by two heads, not actually into the 

 ovipositor itself, but into the membrane (intersegmental) connecting 

 it with tlic sheath — one head into the part reflected on to the ovipositor, 

 the other into the fore portion further outwards. I imagine that the 

 last mentioned muscles act first and retract the ovipositor into the 

 sheath, and that then the other set step iu and, by a concei'ted action, 

 withdraw both ovipositor and sheath within the abdomen. 



Now, as regards the muscles that push the parts out. 



There seem to be no special protrudors of the sheath, their ])lace 

 being supplied by tiie ordinary abdominal muscles that extend the 

 segments upon each other. On the other hand, the ovipositor is pro- 

 vided with a pair of powerful [)rotrudors. They spring from the 

 inner surface of the sheath by a double origin — one from close to the 

 middle line of the dorsum, and the other from further outwards, and 

 are inserted into the points of the inner rods. 



I have little doubt that the muscular system described above 

 is, with some trifling variations, common to all Lepidoptera having 

 simple ovipositors, or compound ones like pronuha, with little 

 range of motion ; but in compound instruments capable of great 

 protrusion, such as we find in the plant-cutters, Coleoplioras, &c., 

 the arrangement is, in many respects, different. The most striking 

 difference, perhaps, is the presence of special protrudors of the 

 sheath, to enable that body to take its fair share in the great 

 extension to which the whole apparatus iu these insects is subject. 

 These muscles spring from the sides of the ventral plate of the 

 7th or last abdominal segment, far back, and are inserted into the 

 points of the outer rods. Their demonstration is by no means easy, 

 and I have only succeeded in obtaining them in an imperfect and 

 fragmentary condition. In strong contrast to them in this respect 

 are the protrudors of the ovipositor. These can be recognised at 

 once, and are of great size, commensurate with the work they have to 

 perform, but with nothing unusual in their attachments. The same 

 may be said of the " proper " retractors of the ovipositor ; but of the 

 common retractors of the ovipositor and sheath, which pass from the 

 points of the rods up into the abdomen, I have not been able (except 

 in Micropterycc) to find a trace, many as have been the preparations I 

 have made, and I can only come to the conclusion that they do not 



