THE BIOLOGY OF THE ALDER FLEA-BEETLE. 257 



DESCRIPTION OF THE STAGES ; MOLTING HABITS AND COLORATION. 



THE EGG. 



Description. Pale orange; ovate-oblong; average length 

 1.25 mm., average width 0.45 mm.; surface densely marked with 

 fine pits. The egg is shown in figure 23. 



Manner and place of deposition. Whenever it is possible, 

 the eggs of this beetle are deposited within the larval tubes of 

 Acrobasis rubrifasciella Packard, a leaf-rolling caterpillar of the 

 family Pyralidae, which is often very common on the alders in 

 Maine. The eggs are laid in the innermost part of the -folded 

 leaf, so that they are completely hidden and the leaf must be 

 unrolled to expose them. Usually the eggs of Altica spp. are 

 streaked with excrement by reason of an instinct which prob- 

 ably has arisen in connection with concealing them ; occasionally 

 the eggs of A. bimarg'mata are so streaked, but usually they are 

 not, probably because, since tfye eggs are already so well pro- 

 tected, such an instinct is unnecessary and has been lost. In 

 a few instances the writer has found the eggs deposited on the 

 under side of a leaf; in such a case they were always placed 

 next to one of the larger veins. In the laboratory, the beetles 

 deposit eggs freely without any attempt at concealment. When 

 first deposited, the eggs are soft and in color dark yellow, but 

 they become bright orange as they harden, and by 24 hours they 

 become the characteristic pale orange. Usually but not always 

 the eggs turn dull gray 24 hours before they hatch. 



The eggs are always deposited in clusters, never singly; a count of 

 90 clusters gave the following data (v stands for variant, or the number 

 of eggs per cluster, and f for the frequency with which that variant 

 occurred) : 



v 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 

 f 67 12 9 16 10 79533 110000 



(v) 19 20 21 22 

 (f) 001 



This shows 6 as the mean of the species, and gives 6.6 as the real aver- 

 age. 



Hatching. Before the egg is ready to hatch, the shell 

 becomes very brittle, and usually the egg turns grayish 24 hours 

 previous to the emergence of the larva, although this is not 

 always the case. Always, however, the lateral tubercles of the 



