isni.] 



183 



Fio. 1. 



because, as the latter much obscures the egg-laying apparatus itself, 

 they are not so favourable for illustration. They all fall under one 

 or other of two divisions, according as they are simple with the 

 abdominal outlet at the 8th segment, or compound with the outlet at 

 the 7th segment. 



Elachista eygnipennella (Fig. 1). — I begin with this, not because it is a com- 

 mon form, for I have met with it nowhere but in the Elachista, but because it is 

 the simplest and most easily understood of any I have come across. It belongs 

 to the class of simple ovipositors. The 8th segment con- 

 sists of a dorsal and a ventral plate ; the dorsal, which 

 is very deep and engages the greater part of the circum- 

 ference of the outlet, receives the stout and slightly 

 curved outer rod into its inner corners, no branches 

 being sent to the comparatively shallow ventral plate. 

 At the extreme inner edge of the ventral plate lies the 

 genital aperture (g. a.), beneath a flat and very narrow arch of chitine. The 

 plates of the ovipositor are large triangular pieces, to which the rods are attached 

 about the middle of the posterior borders. Scattered over the surface of the plates, 

 but congregated most thickly at their outer angle or nose, where, too, they are not 

 so big, are certain long stiif hairs, springing from bulbous bases. They are organs 

 of touch, no doubt highly sensitive, and are to be found in some part or other of all 

 instruments, their usual seat being the ovipositor itself. I shall call them the 

 tactile hairs. 



As we know that eygnipennella must place her eggs on the surface of the blades 

 of Dactylis glomerata and other grasses, it seemed singular that she should be 

 provided with so large and strong an ovipositor, and I was, therefore, led to try and 

 discover her precise practice. I find that she avoids the fully expanded leaves, and 

 selects one in which the sulcus running down the middle of the upper surface is not 

 yet grown out, when, pressing her instrument in between the approximated sides, 

 which must offer no inconsiderable resistance, and guided by the tactile hairs, she 

 deposits her egg or eggs at the bottom of the trench. The egg is cy'indrical and 

 very slender, being nearly three times as long as broad, and slightly iiarrowcr at the 

 tail end. It is usually laid singly, but occasionally three or four in a row over- 

 lapping each other. 



Minoa euphorliata. — This is another example of a simple instrument, showing 

 among other things the division of the outer rods ; a state of things which, I repeat, 

 has only been found among some of the Oeometra. The dorsal and ventral plates 

 of the 8th segment divide the outlet pretty evenly 

 between them, and, to meet this condition, each 

 of the outer rods splits into two, one branch 

 going to the corner of the dorsal plate, the other 

 to the corner of the ventral one (Fig. 3). The 

 plates of the ovipositor are merely bands and 



Sfav) 



Fig. 1.— The last three segments of E. eygnipennella, with the ovipositor protruded, 

 rods. o. r., Outer rods. ^'. a.. Genital aperture 



i. r., Inner 



