2i8 MISS A. L. EMBLETOX ON THE AXATOMY 



this rod is almost tlie same length as the plate, to which it is attached by a hinged joint, 

 as may easily he proved by moving the rod to and fro on the plate-rim. The plate itself 

 carries four long setae, the two inner being the biggest, and the outer the smallest. It 

 is hard to say what is the function of this curious apparatus. I have watched the living 

 insect walkins: about for hours on a fern-frond, hoping to get some clue as to the use of 

 this " tactile plate " ; I have examined its structure microscopically, but cannot be certain 

 of its function. In life, the long hairs were always standing out conspicuously from the 

 side of the abdomen, and occasionally it seemed they were brought into a more erect 

 and bristling attitude, but beyond that I observed nothing. 



Turning now to the ventral elements of the abdominal exoskeleton, it is found that 

 there are six large segments (PL 12. figs. 32, 35). Behind these there are two small sub- 

 circular pieces, one on each side of the base of the sting, and two large pieces still 

 further behind these, nearer the middle line close to the apex of the ovipositoi" ; probably 

 these are the vestiges of the seventh and eighth segments. The ventral plates are 

 almost all alike, except that the one adjoining the petiole has the two horns pointing 

 forwards [cf. petiole). The others all have the lateral parts rounded at the ends, and 

 the surfaces are reticulated and bear fine hairs, becoming more numerous on the 

 posterior segments. The last of the ventral series of plates covers the ovipositor, which 

 is almost entirely hidden in life, though sometimes in a lateral view the tip may be 

 seen protruding slightly (fig. 33). 



I find but little information in books as to the structure of the abdomen of Chalcididse. 

 More attention has been given to the external anatomy of the Acvileata, but the structure 

 of the abdomen in Comys infelix is so different from tliat of the Aculeates that the 

 homologies of some of the parts are still an enigma to me. Bugaion, who dealt with 

 the anatomy of a form allied to Comys infelix, left the diflS.cult points of the morphology 

 untouched ; and he is also silent as to some of the important points of simple anatomy 

 of this part of the body. 



Ovipositor (PI. 12. fig. 41).— The ovipositor or sting has been largely studied in the 

 Aculeata, but I can find little information about it in the Chalcididse. Certain portions 

 of this organ in Comys infelix are so different anatomically from the sting of the 

 Aculeates that it appears at first sight almost hopeless to homologize the two by mere 

 comparison, and it is necessary to thoroughly understand the development to arrive 

 at really permanent results. As regards this a preliminary difficulty exists: it is now 

 generally admitted that the sting of the Aculeates is developed from appendages situate 

 in the pupa on the eleventh and twelfth body-segments, the segments themselves being 

 subsequently very highly modified to form parts of the complex apparatus. Bugnion 

 has figured the ovipositor of Encyrtus fuscicollis, and it agrees largely with what I find 

 to exist in Comys infelix ; he also figures the buds of the appendages in the larva, and 

 shows that they arise in three different segments, viz., the three in front of the anal 

 segment. K this is correct, great caution is necessary in comparing a sting formed by 

 appendages of three segments with a sting that is developed from appendages of two 

 segments only. I have no information to give on this point in Comys, and shall therefore 

 briefly describe the structures I have figured. 



