60 TRANS. ST. LOUIS ACAD. SCIENCE. 



seek, often find this moth, either singly or in pairs, resting with 

 folded wings (Fig. 2, b) within the half-closed flowers. It is then 

 not only hidden, but well protected by the imitative color of the 

 front wings with that of the flower. If we visit the plants after 



" * * * * the garish day 

 Has sped on his wheels of light away," 



and when, with full-blown perianths, the Yucca stands in all her 

 queenly beauty and sends forth her perfume more strongly upon 

 the night air, we shall, with a little patience, meet with this same 

 moth flitting swiftly from flower to flower and from plant to plant 

 — the dusky nature of the hind wings and of the under surface 

 of the front wings almost completely offsetting and neutralizing, 

 when in motion, the upper silvery whiteness of the latter, and 

 thus still rendering the insect a little difficult of detection. It 

 is principally the male which we thus see flying, and by aid of a 

 "bull's eye" we shall find the female for the most part busily at 

 work in the flowers. He, with stronger wing-power, can afford 

 to pass, in the most pleasurable way, the few brief days allotted 

 him ; but she is charged with a double duty, and loses little time 

 in its performance. 



Before she can carry out the maternal task of continuing her 

 race, she must act as foster-mother to the plant in order to insure 

 a proper supply of food to her larvae, which feed on its seeds. 

 With her maxillary tentacle, so wonderfully modified for the pur- 

 pose, she collects the pollen in large pellets, and holds it under 

 the neck and against the front trochanters. In this manner, she 

 sometimes carries a mass thrice the size of her head (Fig. 1, 

 a 1). Thus laden she clings to the top of the pistil, bends her 

 head, thrusts her tongue into the stigmatic nectary and brings the 

 pollen-mass right over its mouth. In this position she works with 

 a vigor that would indicate combined pleasure and purpose — mov- 

 ing her head and body from side to side, and apparently making 

 every effort to force the pollen into the tube. Such is the method 

 by which our Yuccas are fertilized. 



The foregoing account of the insect's habits is founded on re- 

 peated observation ; but we now come to that portion of its career 

 to which I more especially wish to call attention, and which must 

 be considered hypothetical till confirmed by future investigation. 

 Yet I feel as certain of the correctness of my conclusions as 

 though thev had been demonstrated. 



