YUCCA MOTH AND YUCCA POLLINATION. 105 
STRUCTURAL CHARACTERISTICS OF PRONUBA. 
As preliminary to a better understanding of the habits of 
the female, it will be well to draw attention to those 
structural peculiarities which distinguish her from all other 
species of her order and which so admirably fit her for the 
work she hastodo. Pl. 34, Fig. 3 gives some details of the 
head (a) and an important structure which more particularly 
characterizes her and interests us, is the maxillary tentacle 
shown with its palpus at 6. She has a pair of these organs, 
which are prehensile and spinous, and it is chiefly by means 
of these that she is able to collect and hold a relatively large 
load of pollen for the purpose of pollination. Another 
organ which is characteristic is the ovipositor. When 
this is entirely withdrawn, the tip of the abdomen presents 
a truncate appearance, the terminal joint being bluntly 
rounded at the tip with a slight projection both above 
and below and with a corrugated ridge dorsally a lit- 
tle in advance of the tip. This terminal joint is very 
much compressed from the sides, with a few stiff hairs 
around the terminal border. The ovipositor issues from 
the middle of the truncate end and when critically exam- 
ined the basal part, when highly magnified, shows an im- 
bricato-granulate surface, the granulations strongest basally 
and diminishing distally, while the terminal part is smooth, 
long, and peculiarly constructed at the tip, the extreme tip 
being notched or serrate and having a dorsal fin also finely 
and sharply serrate, running anteriorly from it—the whole 
recalling in form the caudal and second dorsal fins of the 
Lamprey (Petromyzon). It thus presents itself, as usu- 
ally exserted when the moth is quickly killed while in 
the act of oviposition; the imbricate basal and smooth 
terminal parts looking like two joints, while the protruded 
portion of the vagina looks like a third and short basal joint. 
The various details shown in Plate 37, Fig. 1 will help to elu- 
cidate the nature of this organ. Ventrally along the ter- 
minal part is seen a membranous duct which broadens just 
