328 



TRANS. ST. LOUIS ACAD. SCIENCE. 



with this powdery matter, which doubtless serves as a protection 

 from the mucilaginous liquid which the- tissues of the Yuccas 

 contain and freely exude upon interference or maceration. Pupa- 

 tion does not take place till the subsequent late winter or spring ; 

 there being, from all that I can ascertain, but one brood each year. 

 The burrow often extends two or more feet below ground, and 

 during the coldest weather the larva probably remains in a par- 

 tially dormant state at the bottom. Occasionally two larvae 

 inhabit the same trunk, in which case their tunnelings are kept 

 separate, side by side. The pupa state (Fig. 28) is generally as- 

 sumed just below the chimney-like funnel at the top of the burrow, 

 and no other preparation is made for it than partial closing, near 

 head and tail, to insure suspension. This funnel is, in reality, built 

 and extended by the larva, and what little matter besides silk 

 goes to make its exterior has been added and worked in from the 

 [Fig. 28.] outside. In the several larvae that I have had 



feeding in breeding-cages, this habit of building 

 up and making tubes, for which remnants of 

 leaves and other extraneous substances are 

 pressed into use, struck me as quite character- 

 istic ; and in one instance I have had such a 

 tube extended over nine inches from the tun- 

 neled trunk, the moss on which the section of 

 Yucca rested being used in its construction. 



In the issuing of the imago the pupa skin is 

 rent on the middle of the notum and across the 

 eyes, and the casings of the legs are never, and 

 * those of the antennae seldom, severed from their 



solderings in the exuvium. 

 The imago rests (Fig. [Fig. 39-] 



29) with its a n t e n n ae 

 slightly diverging and ge- 

 nerally directed forwards ; 

 with the wings elevated, 

 closely appressed, and 

 with the costa of prima- 

 ries at an angle of about 

 45° from the body. Re- 

 garding the flight, which 



is diurnal, Dr. J. H. Melli- Megathvmus vucc.«: .^t rest. 



Megathymus yuc 

 cm : Pupa. 



