RILEY — FURTHER REMARKS ON PRONUBA YUCCASELLA. 571 



cumstances connected with the propagation of the moth." Inci- 

 ted, as he avers, by this expressed belief of Prof. Zeller, Mr, Boll 

 determimed to be one of the "other observers," by carrying some 

 cut Yucca flowers (species not given) containing moths into the 

 house, and placing them in glass cages, where he could observe 

 the doings of the moths. Here is a literal translation of what he 

 says he saw, with a few parenthetical figures of my own adding, 

 to facilitate reference : 



The females bored with the fine, pointed, horny ovipositor into the 

 outer flesh of the pistil, which is certainly not quite soft, but on the con- 

 trary tolerably hard, and about a line thick (i), and laid each time an egg 

 therein. Afterward they generally clambered on to the anthers and 

 scratched the pollen grains out of the cleft of the same with the maxillary 

 palpi so well fitted for the purpose (2). As soon as they had a sufficient 

 quantity formed into a little lump between the roUed-up tongue, thev 

 pushed it into the hole previously made by the ovipositor (3). This oper- 

 tion thej often repeated several times on one and the same pistil, and 

 then wandered to another flower. As Prof. Zeller has just narrated, Rilev 

 observed the same thing in exactly the same way. From this operation, 

 Riley concludes, as I understand it, that the insect fructifies the plant, and 

 even believes that a natural fructification cannot take place (4). 



On which I would remark : (i) Before fructification the pistil 

 is always soft : if unfructified, it remains soft till it wilts and falls ; 

 if fructified, it hardens from day to day. Mr. Boll's specimens 

 were probably already fructified, and the poor moths, unable to 

 obtain the sweets from the nectary, lacked the natural inducement 

 to the act of pollination, which may account, perhaps, for their 

 conduct, as he records it, in working at what little moisture there 

 may have been at the punctures. 



(2) Mr. Boll means, of course, that the pollen was scratched 

 into a lump by the maxillary tentacle, and I hope this testimony- 

 as to the availability of those organs for that purpose will satisfy 

 Prof. Zeller more than my own seems to have done. In reality 

 the moth has little need of scratching, as described by Mr. Boll. 

 Dr. Engelmann has well remarked that the anthers open, con- 

 tract and curl back before the perigon opens, and often expel the 

 large, adhesive pollen grains, which then lie on the inside of 

 the petals, from which the moth may gather them. When not 

 expelled, as is more often the case, they remain in an entire lump 

 on the curled anthers, and the moth, as I have stated (6th Mo. 

 Ent. Rep. 1873) has no difficulty in accumulating her little load. 



