Riley Some Interrelations of Plants and Insects. 



tree Yucca, Yucca fill/era, of northeastern Mexico, reaching a 

 height of fifty feet, with its pendulous panicles five or six feet 

 long, has a very elongate pistil and comparatively short stamens. 

 The few pods which I have been able to examine indicate the 

 presence of a Pronuba and doubtless of a distinct species which 

 will prove very interesting. Yucca baccata, Y. trecuiianea, and all 

 the species which are sufficiently distinctive in characters and in 

 range, may be expected to have special Pronubas associated with 

 them. 



THE BOGUS YUCCA MOTH. 



An interesting fact connected with Pronuba and Yucca polli- 

 nation is that there is always associated with Pronuba yucca*cllii 

 another moth, which bears such a remarkable superficial resem- 

 blance to it, though possessing no power of pollination, that it- 

 has caused much confusion in the 

 past on the part of careless observers 

 and led to a good deal of misstattv 

 ment and error. This is what I have 

 called the Bogus Yucca Moth. /Vo- 

 do.viis (leripic.ii* (Fig. 10). In size it 

 is somewhat smaller, on the average, 

 than Pronuba, and, while found as- 

 sociated with it, appears rather earlier. 

 The female has no maxillary tentacle, 

 but otherwise the genus has all the characteristics which would 

 place it in the same family as Pronuba. The ovipositor is a 

 stronger instrument (Fig. 

 11), but structurally ho- 

 mologous. The eggs are 

 thrust into the stem while 

 yet tender ; they are elon- 

 gate in form, but short 

 and rounded at both 

 ends, resembling the un- 

 developed ova in the ova- 

 ries of Pronuba. The 

 larva is absolutely apo- 



doilS (Fig. 12, a), forms its pm-ont; h, IK.SU! joint of ovipositor; c, it 



<>,- HM1S Within the Stem, <*, terminal joint of sani,-, its tip ^ n,,,,v ,.,,lMnr,.,l: ./ 



' genttaliaofo 5 from side.- <j. <!<> irom above; //, c.^ 



and transforms the ensu- 



ensuinu' vear to a chrysalis, which has a much stronger capitat 



a. / Z \ c. 



FIG. 10. PRODOXUS DECIPIENS: ft. 

 imago, wings closed ; b, female im- 

 ago, wings expanded natural size ; 

 c, enlarged maxillary palpus with 

 its basal tubercle. 



