8 BULLETIN 922, IT. S. DEPARTMENT OF AGRICULTURE. 



mild weather between December 20, 1915, and February 18, 1916. 

 Since eggs laid after November 13, in 1915, failed to hatch the follow- 

 ing spring, it appears that partial development of the embryo previous 

 to cold weather is necessary to enable the egg to survive the winter. 

 Approximately 30 per cent of the eggs overwintering in vials hatched, 

 but it is probable that this is below the normal under natural 

 conditions. 



The eggs, which are a watery yellow when laid, soon grow darker yel- 

 low and early in the fall turn dark in from 2 to 6 days. The last laid 

 eggs may retain their yellow color through the winter, all development 

 being arrested. Early in the fall the eggs that have darkened become 

 sculptured in a day or two, but later on the time elapsing between 

 these changes may be lengthened to weeks or months. The next no- 

 ticeable change in the egg is the rapid pigmentation of the head of 

 the embryo which appears beneath the shell as a distinct round black 

 spot. In the early fall the egg hatches in from 1 to 3 days after this 

 change, although later such eggs may go through the winter in this 

 condition or may hatch during some of the mild winter days. 



During the fall of 1915 the shortest egg period was 13 days, the 

 eggs being laid September 10, and the longest period, excepting for 

 overwintering eggs, was 46 days, the eggs in this case being laid 

 October 21. The average of the records of 50 lots of eggs between 

 September 8 and October 21 was 25.8 days. 



Just previous to hatching the embryos are active within the egg 

 and can be seen moving around. They emerge by cutting a small 

 round hole large enough for the larva to pass through, usually near 

 one end of the egg. The eggshells are never eaten by the larvse after 

 they have emerged. The larvae will commence feeding at once if 

 placed on clover leaves, but may live a long time without food, as in 

 the case of those hatching during the winter. The length of the 

 larval stages is very variable in the fall, for feeding is suspended 

 during adverse weather and resumed in mild. The shortest time 

 secured for the first stage was 13 to 14 days, for the second stage 

 12 to 14 days, and for the third stage 10 days. No fourth-stage larvse 

 were obtained in these experiments during the fall as the cold weather 

 sent the larvse into hibernation. Table II summarizes the lengths of 

 the different stages and larval instars as observed at La Fayette, 

 Ind., in the spring and early summer. 



Numerous larvse were collected on different dates during the 

 winter to determine the ages of the wintering larvse and the results 

 of such collections are given in tabular form in Table III. No 

 adults were found by the authors but Folsom (3) records that hiber- 

 nating adults collected in the spring were much enfeebled and unable 

 to lay eggs. He suggests the possibility of a second generation of 

 beetles farther south which hibernate and oviposit in the spring, 



