116 



The species chosen in the present case is the Nitzschia piilicare^ which 

 is almost invariably to be found in abundance on the common Chimney 

 Swift {ChceUira pelasgia). This bird is an abundant resident of the 

 building in which my laboratory is located, and being readily obtained 

 on account of its tendency to fly in at the windows, I suggested to Mr. 

 P. H. Rolfs, a graduate student in biology, that he attempt the rearing 

 of larvse from eggs with a view to determine the length of develop- 

 mental period in connection with studies of its embryology. 



For this first purpose he secured on two separate occasions a number 

 of the eggs, and kept them, part in a tight pasteboard box in his vest 

 pocket, the others inclosed in cotton-plugged tubes under a hen that 

 was kept in the laboratory at the time for incubating eggs for embry- 

 ological work. Of the tirst lot, all kept in pocket, secured July 27, two 

 eggs hatched August 4, five between August 8-13, one August 16, the 

 last giving twenty days as the longest period. 



Of the second lot secured August 3, six hatched between the 8th and 

 13th, four hatched August 14 (three in box and one in tube), two 

 August 15 (one in box and one in tube), part not hatching, the longest 

 period in this case being thirteen days. 



Assuming that those requiring the longest time had been deposited 

 but a short time before the experiment began, we would have from fif- 

 teen to twenty days as the ordinary time required for the eggs to hatch 

 for this species. 



THE CYPRESS TWIG BORER. 



{Argyresthia cupressella Wlsm.) 



B}^ D. W. COQUILLETT. 



Every spring a large percentage of the cypress trees growing in the 

 city of Los Angeles present a brownish aspect, as if they had been 

 scorched by fire ; this is especially the case with trees allowed to grow 

 naturally and that have not been trimmed. This is the work of a Tin- 

 eid, the larva of which burrows into the tender twigs, causing them to 

 wither and finally to turn brown. The larva enters the twig some dis- 

 tance from the apex, and extends its burrow downward, but thelatter sel- 

 dom exceeds an inch in length, after which the larva deserts it and attacks 

 another twig in a similar manner. Only the smaller and more or less 

 terminal twigs are attacked, these seldom exceeding the size of the 

 lead in a common lead-pencil. The opening of the burrow is usually 

 closed by the blackish castings of the larva, which form a conspicuous 

 object on the outside of the twig. The twigs attacked die back as far 

 as the burrow extends, and when the latter extends into the main twig 

 this also dies back to the point of attack. 



This larva attains a length of about T'""^ is of a light- green color, 

 and in the older ones there is an indistinct, reddish dorsal spot on the 



