SECOND BROOD. 295 



veloped embryos August 26, and eggs were found in the 

 field, Aug. 18, 1894, that contained mature embryos 1.4 mm. 

 long. Notwithstanding this early development of the em- 

 bryo, up to this year no eggs were found to have hatched 

 in the fall, though a careful watch was kept for them. In 

 Europe fall hatching is reported in at least one instance. 

 Ratzeburg, in " Die Forst-Insecten," Vol. II, page 112, says : 

 " Here they remain [on the branches] much like a long mass 

 of fungus until the next April or May, or by exception they 

 hatch in the autumn, as I have seen them myself on the 

 5th of September, 1836." 



A Second Brood. 



In the early part of September, 1895, many of the gypsy 

 moth egg-clusters were found to be hatching at the " Win- 

 ning" colony, in Woburn, where the caterpillars had com- 

 mitted serious depredations during the summer months. 

 The second brood, which appeared only in this particular 

 colony, seemed to have hatched because of peculiar condi- 

 tions of location and temperature. The colony is situated 

 on the side of a hill, sloping towards the south, which is 

 covered with a dense growth of medium-sized oak trees. 

 When this colony was discovered, in the early part of the 

 summer, the caterpillars were much larger and more nearly 

 ready to pupate than in any other colony, and this led to the 

 opinion that the eggs must have hatched much earlier than 

 in other localities. Many of the moths emerged and laid 

 their eggs at this place before the caterpillars in other colo- 

 nies, where the conditions for rapid development were not 

 as favorable, had commenced to pupate. 



While embryonic development in this insect appears to be 

 more rapid in warm weather, a limited number of experi- 

 ments performed in 1893 and 1894, seem to indicate that a 

 certain degree of cold is probably necessary to mature the 

 embryo. In the latter part of August on several nights the 

 temperature fell quite low in the eastern part of the State, 

 and on one night a frost occurred in some places. iVt this 

 time a part of the eggs in the " Winning"' colony had been 

 deposited from four to six weeks, which was sufficient time 

 for the development of the embryo. This cool weather was 



