566 TRANS. ST. LOUIS ACAD. SCIENCE. 



Additional Notes on Megathymus yucc^;. 



By Charles V. Riley. 



[Read Nov. 5, 1877.] 



Having reared this insect from the egg to the imago since the 

 publication of the first article (p. 323, ante), I am able to give 

 some additional facts, part of which appeared in my last State 

 Report. There is but one generation annually, and the charac- 

 teristic glistening powder that covers the full-grown larva is not 

 secreted till toward the last molt. The habit of living at first 

 within a cylinder made with one of the rolled leaves, webbed 

 across with silk, is very marked, and even where the larva at first 

 works at the base of a leaf, it will web the leaf and feed along up 

 to its tip before entering into the more solid portions of the plant. 

 In extruding the excrement the larva backs up to the end of the 

 retreat, which is kept only partially closed. 



Where several larvae hatch out on the same plant (which not 

 unfrequently happens), there is a struggle as to which shall usurp 

 the privilege of entering the stem, and the first one to do so gene- 

 rally keeps the others out on the leaves, so that in the end they 

 doubtless perish. The parent is by no means particular as to 

 where she fastens her eggs, for Dr. Mellichamp has sent me dry 

 leaves of Quercus falcata that had accumulated around his Yuccas 

 and that have eggs fastened to them. 



One larva I kept for a long time in a tin box, occasionally sup- 

 plying it with fresh leaves. It formed a perfect cylinder of silk 

 and excrement around the bottom of the box, fastening thereto 

 the ends of the cut leaves, so that the cylinder was necessarily 

 broken each time the leaves were changed. This specimen went 

 through no less than seven molts at irregular intervals of 10, 11, 

 24, 14, 61, 15 and 21 days respectively. It changed but little in 

 appearance, except in becoming somewhat paler, after the second 

 molt, and died when about three-fourths grown — death resulting, 

 I think, more from the mould that formed from the excrement, 

 and which it was impossible to prevent, than from the nature of 

 its food. It is doubtful if so many molts are suffered in more 

 natural and healthy conditions. 



Another specimen that entered a Yucca plant, in the garden 

 of Dr. G. Engelmann, throve admirably, extending over a foot 



