CCX1 



shown in column four. The differences between the theoretical and ob- 

 served values, is given in the column d. It will now be seen that column 

 e also agrees even more satisfactorily with the theoretical values, the dif- 

 ferences being given in the last column. 



By allowing a definite interval of time to elapse between the giving and 

 writing of the number, Mr. Nipher proposes to obtain numerical esti- 

 mates of the power of memory. 



Mr. Riley treated of the oviposition of Leucania untpuncta, or 

 the Army-worm moth. 



In his Sth Annual Report, the last forms of which were going through 

 the press, he had remarked that " at first view it seems singular that the 

 eggs of an insect that appears in such countless myriads from Maine to 

 Georgia, and from Virginia to Kansas, should have remained undiscov- 

 ered either by farmers or entomologists. One of the obstacles that have 

 stood in the way is, that, as soon as the worms have increased so prodi- 

 giously as to attract attention, their natural enemies become so multiplied 

 that a very small per cent, of the worms entering the ground issue again 

 as moths. A second reason is that during the season when the insect is 

 not numerous, and attracts no attention, no one thinks of searching for 

 the eggs. A third reason is that the moths that are reared indoors do not 

 oviposit in confinement. I venture to suggest a fourth possible reason 

 that has hitherto occurred to nobody : it is that the eggs are for the most 

 part secreted where they are not easily seen." 



Structure is a trustworthy guide to habit, and Mr. Riley had been led 

 to this last conclusion by study of the structure of the ovipositor of the 

 moth in question. The time, place and manner of oviposition in this spe- 

 cies is quite important from the economic point of view, as the insect may 

 readily be destroyed in the egg state by fire, if the conclusions drawn are 

 correct. 



Mr. Riley had recently been able to verify the correctness of his conclu- 

 sions by direct observation, having witnessed the mode of oviposition on blue 

 grass. The eggs are, as he surmised, secreted, being either glued in rows of 

 from 5 to 20 in the groove which is formed by the folding of the terminal 

 grass-blade, or in between the sheath and the stalk. In exceptional cases 

 they may be pushed into crevices in the ground. The eggs are white, 

 slightly iridiscent, spherical, and only T £ w of an inch in diameter. They 

 are fastened to each other and to the leaf, and covered along the exposed 

 portion, by a white, glistening, viscid substance. As they mature the 

 color becomes more sordid or yellowish, and by the seventh day after 

 deposition the brown head of the embryon shows distinctly through the 

 shell. The larva hatches from the eighth to th etenth day, measures 

 1.7 mm. in length, is dull, translucent white in color, with a large brown- 

 black head, and is a looper, the two front pair of abdominal prolegs being 

 atrophied. On account of its extremely small size and of the color resem- 

 bling the pale bases of the grass-stalks near the ground, it is almost im- 

 possible to find them even where there are dozens to the square foot. 



