THE CATERPILLAR. 299 



From studies made on a large number of egg-clusters in 

 the insectary, supplemented by observations in the field, it 

 was discovered that in many cases some part of the eggs 

 composing an egg-cluster did not hatch. Seven large egg- 

 clusters which had hatched were found to contain on an 

 average 124 unhatched eggs, the smallest number being 43, 

 the largest 224. A small number of unhatched eggs is found 

 in nearly all the old nests taken in the field. 



The Larva or Caterpillar. 



Relative Vitality of Caterpillars hatching at Different Times 

 from the Same Egg-cluster. 



The following observations were made under my directions 

 by Messrs. Minott and Mosher, both careful and reliable 

 observers : — 



From a large cluster of eggs, laid by a single female 

 gypsy moth, and kept in a warm room, 4 hatched late in the 

 afternoon of March 11, 1894; at 10 a.m., March 13, 333 

 more eggs had hatched ; at 5.20 p.m., 194 more had hatched ; 

 March 14, 233 had hatched; March 15, at 4.35 p.m., 48 

 more eggs had hatched ; March 19, 10 more hatched ; March 

 20, 3 ; and on the 21st, 6 more eggs hatched, making 831 

 eggs hatched from this cluster. The caterpillars were re- 

 moved as soon as hatched. 



Fifty caterpillars were selected, as follows: 10 of those 

 hatched on the second day, 10 of those hatched on the third 

 day, 10 of those hatched on the fourth, 10 of those hatched 

 on the eighth and 5 of those hatched on the ninth and tenth 

 days, making 6 sets of caterpillars taken from those which 

 hatched at different times. Each caterpillar was fed on let- 

 tuce, in a box by itself, and under as nearly similar con- 

 ditions as possible, careful records being made, for the pur- 

 pose of learning whether there was any difference in the 

 vitality of caterpillars hatched at different times, from the 

 same egg-cluster ; the period of rest before and after each 

 molt, and the time between each molt. No perceptible dif- 

 ference was noticed in the vitality of those hatched at differ- 

 ent times. It was observed that they all ate equally well 

 and appeared equally healthy, and that all their transforma- 



