4 BULLETIN" 235, U. S. DEPARTMENT OF AGRICULTURE. 



mined at the Sacramento laboratory during June, July, and August, 

 1913, as follows: Egg stage, 6 days; larval stage, 35 days; pupal 

 stage, 12 days; adult, about 14 days. Total, from egg to adult, 53 

 days, or 1 month and 23 days. 



While the subject of this article is practical and based on condi- 

 tions at Sacramento, Cal., it should be added that in the case of the 

 life history of this species Dr. Chittenden has pointed out * that ''ex- 

 periment shows that the insect is capable of passing through all its 

 several stages from egg to adult in five weeks, which furnishes a pos- 

 sibility of six or more generations in a well-heated atmosphere, 

 although in a moderately cool granary or other storehouse four or five 

 broods is probably the normal number per annum." 



The sudden appearance of large numbers of larvae in dried fruit 

 is readily explained by Table I, which shows the number of eggs 

 deposited by six moths which were confined in the laboratory to 

 determine the rate of oviposition. 



Table I. — Egg-laying records of the Indian-meal moth. 



No. 



Days. 



Total. 



1st. 



2d. 



3d. 



4th. 



5 th. 



6th. 



7th. 



8th. 



1 

 2 

 3 

 4 

 5 

 6 1 -.. 



46 

 56 

 39 

 16 

 59 



79 

 65 

 43 

 33 

 51 



36 

 27 

 34 

 47 

 55 



23 

 36 

 18 

 64 

 38 



24 

 36 

 16 

 45 

 26 



16 

 21 



6 

 56 



5 



11 

 9 





235 

 250 

 156 

 286 

 234 

 168 



12 



13 

























1 The number of eggs in this vial was determined as total and not by days. 

 Average number of eggs deposited by the six moths, 221.3. 



These eggs were deposited mostly during the night. 



The life cycle during the summer, as given in a preceding para- 

 graph, is only 53 days. Starting with one fertile female in a packing 

 house on June 15 (provided all of the insects matured), there would 

 be 221 moths by the following August 15, and by August 30 (pro- 

 vided that half of these moths were females) there would be a total of 

 23,310 larva? in the dried fruit. 



Under natural conditions some of the eggs do not hatch and many 

 of the larva? fail to mature, but from the foregoing data it is readily 

 understood that a few moths of this species are capable of producing 

 a very severe infestation within a relatively short time, provided that 

 temperature and other conditions are favorable. 2 



i Chittenden, F. H. Some Insects Injurious to Stored Grain. U. S. Dept. Apr., Farmers' Bui. 45, 24 

 p., 18 fig., 1897. See p. 10. 



2 The hymenopterous parasite Tlabrobracon hebelor Say is frequently found attacking the larv;r of the 

 Indian-meal moth, but it has not been observed appreciably to affect the infestation in California. 



