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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
The newly hatched larva is pink with dark yellow head. The full-grown larva is 
light grey and about one centimeter in length. It has rows of hairs with round, 
semitransparent tips. If the leaves on which they are feeding are disturbed the larvae 
fall to the ground. The larval period lasts from 11 to 14 days. The prepupal stage 
lasts one day. The pupa is yellow until shortly before emerging. The pupal stage is 
spent underground and lasts 7 days in most cases, 6 days in one instance. The adult 
remains in the pupal cell a few hours until the wings are hardened, then crawls out 
and begins feeding on the leaves. 
The total time from newly hatched egg to adult was usually 26 days. In three 
days more the adults were mating. 
Ralph E. Danforth, College of Agriculture and Mechanic Arts, 
May agile z, P. R. 
Hydrocyanic Acid Retained by Fumigated Cheese. Messrs. E. R. de Ong and 
C. L. Roadhouse have recently published the recommendation that cheese may be 
fumigated with hydrocyanic acid gas for the destruction of certain cheese pests 
(“Cheese Pests and Their Control,” Calif. Exp. Sta. Bui. 343, May, 1922). The 
•ability to use this gas with safety in cheese rooms without removing the cheese is 
much to be desired and in connection with his work with the cheese skipper ( Pio- 
plnla casei L.) the writer made several preliminary tests of the advisability of using 
this fumigant. He is indebted to Dr. R. E. Holm, Division of Virus-Serum Control, 
Bureau of Animal Industry, U. S. D. A., for the analyses of the fumigated cheese. 
A review of the experiments and results follows. 
Oct. 10-11, 1921. Fumigating box, 100 cu. ft.- Charge 4 oz. NaCN, 6 oz. H 2 S 04 , 
8 oz. water. Temperature at start about 55° F.; relative humidity about 80%. 
Exposure of cheese 10:30 A. M. to 8:45 A. M. Cheese tested: Camembert, Cheddar 
and Swiss, the pieces being roughly 3x3x3 inches. One side of each piece freshly 
cut and marked. Gas not strong when box opened, x^nalvsis showed considerable 
HCN in the cheese, especially in the Camembert; least in the Cheddar. The gas in 
the cheese much reduced after airing for about one day. 
Oct. 17-18, 1921. Fumigating box the same, but repaired to reduce leakage. 
Charge 2 oz. NaCN, 3 oz. H 2 SO 4 , 4 oz. water. Temperature about 63° F.; relative 
humidity 89%. Exposure of cheese 3:00 P. M. to 9:30 A. M. Gas strong when box 
opened. Cheese tested, same as in first trial. Analyses showed that a large amount 
o f acid was retained, even after airing for about one day. After this airing, more 
acid was present in the center of the cheese than near the surface, due, probably, to 
slower dissipation from within. 
Oct. 18-19, 1921. Fumigating box the same. Charge 1 oz. NaCN; \y 2 oz. 
H 2 SO 4 , 2 oz. water. Temperature about 65° F.; relative humidity 80%. Exposure 
of cheese 11:00 A. M. to 10:00 A. M. Temperature steadily declined to 55° F. at 
end of trial. Migrant skipper larvae used as indicators of efficiency of the fumigation 
were killed; these were exposed in Petri dishes. Cheese aired for 24 hours before 
being sent to Dr. Holm’s laboratory. Analyses showed that HCN was found in all 
the samples, but the concentration in the Cheddar amounted to a mere trace. 
On account of the tenacity with which skipper larvae cling to life in the presence 
of hydrocyanic acid gas, especially when embedded in their food materials, the writer 
feels that dosages up to and including one ounce per 100 cu. ft. would be largely 
wasted. Cheese mites also are reported to be very resistant to this gas. It would 
