THE BIOLOGY OF THE ALDER FLEA-BEETLE. 261 



shows through. In a few hours pigment is formed in the tuber- 

 cles and in the nodules. As the body wall is not stretched, the 

 tubercles and the nodules lie very close together, and give the 

 larva a dark aspect; late in the instar, the general color of the 

 larva is much lighter, since the integument is stretched, the 

 nodules farther apart, and the tubercles smaller in proportion 

 to the body surface. 



Such a series of color changes is very characteristic of all 

 of the species of Altica which the writer has studied. They are 

 either white or yellow after a molt (according to the color of the 

 fat-body), as there is no pigment in the cuticula; they rapidly 

 become darker, and the darkness is at a maximum a few hours 

 after the molt; they become gradually lighter throughout the 

 instar, and the coloration of the early and late part of the same 

 instar is quite different in some species. 



Description of the newly hatched larva. The coloration 

 and setal arrangement (with the exceptions noted below) is the 

 same in the newly hatched larva as it is in the mature larva; 

 however the tubercles are proportionately much larger, and the 

 cuticular nodules much closer together. The setae are distinctly 

 capitate all through the first instar. 



There are only 3 setae on the lateral tubercles of the meso- 

 thorax and the metathorax, instead of 4, as in the full-grown 

 larva; and only 2 on the lateral abdominal tubercles instead of 

 3; and only one on the posterior dorso-lateral tubercles of the 

 8th abdominal segment instead of 2. 



This condition is characteristic of the second instar larvae 

 as well as those of the first instar; and not infrequently this 

 same condition prevails in a full grown larva. 



Head measurements of larvae. 



1st instar. 



Minimum .38 mm. 



Maximum .43 mm. 



Mean .43 mm. (21 specimens.) 



Average .42 mm. (42 specimens.) 



2nd instar. 



Minimum .64 mm. 



Maximum .71 mm. 



Mean .64 mm. ( 5 specimens.) 



Average .67 mm. (10 specimens.) 



