372 



only specifically but geiierically, they are derived from one and the same ancestral 

 lorm? Pronuba, depending for its existence upon the pollination of the HoAver, is 

 profoundly modified in the female sex in adai)tation to the peculiar function of pol- 

 lination, Prodoxns, dwelling in the fiesh of the fruit or in the flower stem, and only 

 indirectly depending upon the fructification of the plant, is not so modified, but has 

 the ordinary characters of the family in both sexes. In the former the larva quits 

 the capsules and burrows in the ground; it has legs to aid in its work, while the 

 chrysalis is likewise beautifully modified to adapt it to prying through the ground 



7? S" 



W 



! 



Fig. 71. — Peodoxus decipiens: a, larva; 6, head from above; c, (i, left jaw and antenna; e, pupa; 

 /, infested stem cut open to show the burrows, castings, cocoons, and pupa shell (h) ; all enlarged but 

 /, the hair line between a and e showing natural length. 



and mounting to the surface. The latter, on the contrary, never quitting the stem, 

 has no legs in the larva state, and in the chrysalis state is more particularly adapted, 

 by the prominence of the capital projection, to piercing the slight covering of the stem 

 left ungnawed by the larva. The former is very regular in its appearance as a moth 

 at the time of the flowering of the Yuccas in their native range. The latter appears 

 earlier, as the food of its larva is earlier ready, and the female could not oviposit in 

 the riper stem. 



OTHER SPECIES OF PRODOXUS. 



Some ten species of this genus Prodoxus have been described, all of 

 them having the very same structural characteristics and in the adoles- 

 cent states being scarcely distinguishable. Prodoxus decipiens is asso- 

 ciated with Pronuba yuccaseUa east of the liocky Mountains, and 

 Prodoxus sordidus is similarly associated with Pronuba synthetica, breed 

 ing in the flower-stems of Yucca brevifoUa. All the other species are 

 associated with Pronuba macuJafa, breeding either in the base of the 

 capsules or in the flower stem or the main stem of Yucca ivliipplei. I 



