70 U-S. NATIONAL MUSEUM BULLETIN 255 



larvae were found in cocoons, along with a large number of larvae 

 which had died previously. 



All known members of Prodoxus overwinter as last-instar larvae 

 in their burrows. Prior to hibernation, the larva generally excavates 

 a burrow to the outer layers of the stem, leaving a thin partition 

 blocking the future exit. It then retreats back into its burrow and 

 constructs a cocoon of white silk, which is covered externally with 

 larval excrement and tiny plant fragments. 



Pupation. — Pupation occurs in the yucca stalk (or fruit) during 

 spring, prior to the flowering period of the host. The pupal period 

 is relatively brief and probably does not exceed a week or so in length. 

 Immediately prior to adult emergence, the pupa forces its way through 

 the thin partition sealing the exit (fig. 28). After it has pushed itself 

 about halfway out of the burrow, the adult is able to emerge. This 

 activity normally occurs late in the evening, at about dusk. 



Structurally, the pupae of Prodoxus and Tegeticula are quite dis- 

 similar, and are modified in accordance with their different life 

 histories. The pupa of Prodoxus (fig. 25) is relatively smooth and 

 lacks the conspicuous dorsal spines of Tegeticula. Prodoxus further 

 differs in having a frons more projected and conelike. These adap- 

 tations probably aid the pupa in forcing its way through the cuticular 

 partition of its burrow, as well as facilitate its emergence from the 

 cocoon. 



Adult. — Emergence of the adults usually occurs in April, May, or 

 early June. The first specimens may appear before any yuccas are 

 flowering and prior to the emergence of Tegeticula, but they are most 

 abundant during the flowering period. Copulation has not been ob- 

 served but probably occurs soon after emergence along the yucca 

 stalk and in the flowers where the adults usually rest during the day. 



Immediately prior to oviposition, the female normally settles 

 lengthwise on the yucca stalk with her head directed upward. Raising 

 her abdomen, she then proceeds, usually with some difiiculty, to 

 force her ovipositor into the plant. Several abortive attempts may 

 be made over the general sm-face of the stalk before an area is located 

 where the ovipositor can be inserted. The oviduct and ovipositor 

 of Prodoxus are considerably shorter than those of Tegeticula; con- 

 sequently, penetration into the plant is not as deep. 



RUey (1892a) reported that the plant tissues surrounding the egg 

 of P. quinquepunctellus seem to experience some disorganization 

 through its presence, as in the case of Tegeticula. For most species 

 of Prodoxus, no serious deformations or retardation of plant growth 

 appear other than a slight discoloration of the stem at the point of 

 oviposition, which later develops into a small scar. The larvae 

 (adult female ?) of P. y-inversus, however, have been reported (Riley, 



