39 



worm very closely. Prof. Riley's description of the Cabbage Plusia 

 is as follows : 



"Pale yellowish translucent green, the dorsum made lighter and 

 less transparent by longitudinal opaque lines of a whitish-green ; 

 these consist each side of a rather dark vesicular dorsal line, and 

 of two very fine light lines, with an intermediate broad one. 

 Tapers gradually from segment 1-10, descending abruptly from 11 

 to extremity. Piliferous spots white, giving rise to hairs, some- 

 times black, sometimes light colored ; and laterally a few scattering 

 white specks in addition to these spots. A rather indistinct nar- 

 row, pale stigmatal line, with a darker shade above it. Head and 

 legs translucent yellowish-green, the head having five minute black 

 eyelets each side, which are not readily noticed with the naked 

 eye. Some specimens are of a beautiful emerald green, and lack 

 entirely the pale longitudinal lines. Described from numerous 

 specimens." 



From this it will be seen that these two worms resemble each 

 other very closely, and the only character that I am able to point 

 out by which the one may be distinguished from the other is the 

 black ring, or annul ation, around the spiracles of the Celery-worm, 

 this ring not occurring in the Cabbage Plusia, at least Riley makes 

 no mention of it, and in comparing the Cabbage Plusia with an 

 allied species, he says : 



"There is another worm which may be known as the Thistle 

 Plusia. and which occurs on our common thistles, and cannot 

 therefore be considered very injurious. It differs only from that 

 of the Cabbage Plusia in having the sides of the head, the thoracic 

 legs, a row of spots above the lateral light line, and a ring around 

 the breathing pores, black. I have bred from it the Plusia preca- 

 tionis of Guenee — an insect whose larval history has not hitherto 

 been known." 



It would appear from this that the spiracles, or breathing pores, 

 of the Cabbage Plusia are not ringed with black. I have also bred 

 the Thistle Plusia, and my specimens did not differ from those bred 

 by Prof. Riley, except in lacking the row of black spots above the 

 lateral or stigmatal light line. 



On the 17th of May, 1880, I enclosed a female Celery-worm Moth 

 in one of my breeding cages in which some grass, clover and plan- 

 tain were growing. In the afternoon of the next day she laid about 

 fifty eggs, placing them singly or in small rows, or patches, on 

 both the upper and under sides of the grass and plantain leaves, 

 seldom placing more than four eggs in one cluster. Shortly after 

 hatching, the larva ate the parenchyma of the blades of grass, leav- 

 ing the veins untouched ; after increasing somewhat in size they fed 

 upon the plantain leaves. 



The first larva of this brood began spinning its cocoon on the 

 evening of June the 16th; it became a chrysalis June the 19th, and 

 was changed to a moth on the 28th of the same month. The chry- 

 salis could easily be seen through the thin cocoon. 



When this larva began to spin its cocoon the other larvae hatched 

 out at about the same time, and reared under precisely similar con- 

 ditions, were of all sizes from those only one-half grown to those 

 nearly full grown. As they appeared to be costive, I supposed that 



