24 



BULLETIN 1238, IT. S. DEPARTMENT OF AGRICULTURE 



under flakes of bark, or in crevices or cracks, wherever such are 

 found. The flexible and protrusible terminal segments of the abdo- 

 men are used as an ovipositor, which is capable of thrusting the eggs 

 into very small crevices and quite a distance into the deeper and more 

 extensive cavities. When placed under a bit of bark which has be- 

 come somewhat loosened, the eggs are usually stuck to the inner sur- 

 face of the bark, rather than to the outer surface of the wood from 

 which it has separated. In some cases the eggs are placed in compact 

 clusters; in others they are apparently thrust in at random. The 

 greatest number of eggs laid by any female in captivity in the in- 

 sectary at Wallingford was 250, which hardly represents the egg- 

 laying capacity of the average moth. As the result of dissections, 

 Wellhouse (36) records finding an average of 401 eggs each in the 

 abdomens of 12 moths, and one of them contained 676 eggs. 



In the protection of the insectary cages, most of the moths lived 

 from one to two weeks, one female living 24 days. Under field con- 

 ditions the length of life is probably not so great. 



INCUBATION OF EGGS. 



The incubation period varies to a considerable extent, the earliest 

 laid eggs usually being subjected to cool weather which retards the 

 development of the embryo larva. For this reason, hatching is likely 

 to cover a shorter period of time than egg-laying. Table 10 gives 

 data regarding incubation of eggs in 1920 and 1921. 



Table 10. — Incubation of eggs of the spring canTcerworm, 



1920 and 1921. 



Wallingford, Conn., 



IN 1920. 



Eggs laid— 



Mar. 31. 



Do. 



Do. 

 Apr. 1.. 



Do. 

 Apr. 2.. 



Do. 

 Apr. 5.. 



Do. 

 Apr. 12. 



Do. 

 Apr. 13. 



Do. 



Do. 

 Apr. 15. 



Eggs 

 hatched — 



May 17 



May 18 



May 19 



May 18 



May 22 



May 18 



May 19 



May 18 



May 19 



...do 



May 22 



May 19 



May 20 



May 21 



May 19 



Number 

 of eggs. 



Incu- 

 bation 

 period. 



Days. 



Eggs laid- 



Apr. 15. 



Do. 

 Apr. 21. 



Do. 



Do. 



Do. 

 Apr. 22. 



Do. 



Do. 



Do. 



Eggs 

 hatched- 



May 20 

 May 22 

 May 21 

 May 22 

 May 23 

 May 24 

 May 22 

 May 23 

 May 24 

 May 25 



Number 

 of eggs. 



Maximum period 



Minimum period 



Average period 



Total individuals, 416. 



Incu- 

 bation 

 period. 



Days. 

 35 

 37 

 30 

 31 

 32 

 33 

 30 

 31 

 32 

 33 



51 

 30 

 37. < 



Mar. 19. 



Do. 



Do. 



Do. 



Do. 

 Mar. 20. 



Do. 



Do. 



Do. 



Do. 

 Mar. 21. 



Do. 



Do. 



Apr. 24 



2 



36 



Apr. 25 



5 



37 



Apr. 26 



4 



38 



Apr. 27 

 May 2 



3 



39 



1 



44 



Apr. 22 



1 



33 



Apr. 23 



7 



34 



Apr. 24 



78 



35 



Apr. 25 



105 



36 



Apr. 26 



5 



37 



Apr. 25 



11 



35 



Apr. 26 



13 



36 



Apr. 27 



1 



37 



Mar. 21. 

 Mar. 25. 

 Mar. 26. 



Do. 

 Mar. 27. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 Mar. 28. 



Apr. 28 



2 



Apr. 27 



6 



...do 



8 

 4 



Apr. 28 



Apr. 23 



1 



Apr. 24 



2 



Apr. 25 



13 



Apr. 26 



2 



Apr. 27 



2 



Apr. 28 



94 



Apr. 29 



9 



Apr. 30 



1 



Apr. 28 



32 



