100 JOURNAL OF THE [October, 



When searching for information about the shape of the con- 

 stituent parts, I could find only a few descriptions and sketches, 

 and all of them were so indefinite that it was evident they were 

 made more by employment of imagination than of actual obser- 

 vation. It is therefore interesting to study the shape of these 

 parts, and their working together for their intended purpose. 

 By means of the microscope we can see that the parts are 

 barbed in different ways, as I showed at the meeting of January 

 4th, 1889. But, besides several lighter and darker shaded lines, 

 we cannot find out much that is instructive about the form of 

 the interior. The preparation of cross-sections does not furnish 

 very promising results, because chitine— the main substance of 

 the ovipositor — is so hard and brittle that out of a considerable 

 number of sections sometimes none will show enough for an 

 explanation. As the imago of the insect gave so little hope for 

 success, I tried different states of development of the pupa, up 

 to the time when the imago is just emerging, and this last state 

 gave the best results. 



The chitine skeleton of insects develops to the proper shape 

 while the insect lies dormant as a pupa, and is still soft when the 

 imago emerges, but hardens in a few hours, when out of the 

 pupal skin. I had on hand a few cocoons of the large 

 moth, Platysamia cecropia, infested with a brood of Cryptus 

 samice Pack., belonging to the family Ichneumonida^, and thus 

 I succeeded in procuring the different states of development. 

 This insect gives the following approximate measurements : 

 length of head, thorax and abdomen, 10 mm.; expanse of wings, 

 16 mm.; length of antennas, 5 mm.; length of ovipositor, 6 

 mm,; diameter of the same, 0.2 X o.i mm. 



The ovipositor, on the cross-section, shows that it is composed 

 of four tubes, which are so compressed as to give an oval shape. 

 The four tubes are all separated from each other, excepting the 

 two dorsal ones. These are fastened together along the dorsal 

 line into one single piece. At the line of contact between the 

 dorsal and the ventral parts, the dorsal part has two projections 

 or tongues, each one having the shape of the capital letter, 

 "T." These T-shaped tongues are fitted into grooves of the 

 same shape in the ventral parts. By this arrangement the dorsal 

 and the two ventral parts can slide alongside of each other, as far 

 as the muscles inside the abdomen will allow ; but, by the same 



