4 BULLETIN 873, U. S. DEPARTMENT OF AGRICULTURE. 



in figures 1, b, and 2. The female moth lays eggs in accumula- 

 tions of flour, up and down elevator legs, throughout spouts, around 

 dust collectors, in bolters, purifiers, etc. From these eggs hatch the 

 larvae or worms. When full grown, the larvae are about half an 

 inch long and are whitish or pinkish in color, with minute black dots 

 and fine hairs, as shown in figure 1, c, e. When full grown the larvae 

 spin cocoons in which they transform into the reddish brown pupa? 

 shown in figure 1. d. From these pup* emerge the parent moths 

 of the next generation. 



LENGTH OF LIFE FROM EGG TO ADULT. 



Dean 2 states that when the temperature ranges from 85° to 90° F., 

 the eggs of the moth hatch in about 3 days, the larvae become full 

 grown in about 40 days, and the pupal stage requires from 8 to 12 days 



more. Under ordi- 

 nary flour-mill condi- 

 tions about 9 weeks 

 are required for the 

 pest to pass through 

 its life cycle from egg 

 to adult. Length of 

 the life cycle varies 

 greatly with the tem- 

 perature. At temper- 

 atures lower than 55° 

 F. activity is sus- 

 pended. During most favorable temperature conditions, 24 days has 

 been found by Chittenden 3 to be the minimum required for larval 

 development. 



LARVAL HABITS MAKE MOTH MOST SERIOUS PEST. 



The Mediterranean flour moth is the most serious of all mill pests, 

 not so much because of the food values it actually consumes, but be- 

 cause the larvae or worms construct in the flour silken tubes in which 

 the}- live, spin a fine silken thread wherever they crawl, and spin co- 

 coons in and about the machinery and stock. As they grow older they 

 spin increasing amounts of silk until, when the)' are full grown, the 

 quantity of web they spin in crawling about machinery, sacks, etc., in 

 search of a suitable place to spin cocoons is enormous, and causes a 

 bad webbing or matting of the flour. These masses of webbed flour 

 receive during the operation of the mill fresh layers of flour, which 



e 



Fig. 1. — Mediterranean flour moth : a, Moth ; t, same 

 from side, resting ; c, larva ; d, pupa ; e, abdominal seg- 

 ments of larva. The hair lines by a, c, and d represent 

 the actual length of the forms. (Chittenden.) 



- Dean, G. A., mill and stobed-gbain insects. Kans. State Agr. Coll. Exp. Sta. Bui. 

 1-'.'. p. 22t;-227. July, 1913. 



"CHITTENDEN, F. II., TIIE DEVELOPMENT < >F THE .MEDITERRANEAN FLOUR MOTH. In 



V. S. Dept. Agr. Div. Ent. Bui. 6 (n. s.), p. 85-88, 1896. 



