juneio, i9i8 Physical Properties Governing Contact Insecticides 527 



(Plodia inter punctella Hbn.), and certain aphids. The methods of pro- 

 cedure were as follows: The liquid to be tested was stained with 

 Sudan III or trypan-blue, both of which are colloids, and therefore will 

 not pass through a semipermeable membrane. The cockroach was 

 placed into the liquid and allowed to remain for from 15 minutes to 2 

 hours, depending upon the viscosity of the liquid. After a sufficient 

 time had been allowed for the liquid to penetrate, the cockroach was 

 removed and opened on the ventral side. The tracheae which, were 

 penetrated by the material stood out either red or blue, and it was very 

 easy to determine the extent of the penetration. 



Table I gives a list of the materials used and shows their power of 

 penetration. The letters represent the distance the material penetrated 

 into the tracheae as illustrated in figure i. 



Table I. — Materials used in experimental work, showing their power of penetration 



Distilled water 



Saponin solution (i : 500) 



Gelatin solution (i: 1,000). . . . 



Nicotine solution 



Glycerin 



Lime-sulphur solution 



Alcohol (50 per cent) 



Milk 



Ivory soap (1:150 at 24'' C). .. 



Croton oil 



Lubricating oil 1 1 



Nicotine 



Acetic acid 



Furfurol 



Soft soap (1:150 at 24° C.) 



Yellow soap (1:150 at 24° C). . 

 Ivory soap (1:150 at 36° C). .. . 



Oil of tar 



Cassia oil 



Clove oil 



Lubricating oil 7 



Boiled linseed oil 



Lard oil 



Castor oil 



Absolute alcohol 



Trimethylene cyanid 



Nitrobenzene 



Methyl salicylate 



Quinolin 



Oleoresin of black pepper 



Castile soap (1:150 at 24° C). . 



Cedar oil 



Fish oil 



Petrolatum 



Amyl alcohol 



Oil of bitter almonds 



Whale oil 



Eugenol 



Lubricating oil 5 



Penetra- 

 tion.o 



o 

 o 

 o 

 o 

 o 

 o 

 o 

 o 



A 

 A 

 A 

 A 

 A 



A to B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 

 B 



B to C 

 C 

 C 

 C 

 C 

 C 

 C 



C to D 

 D 

 D 



D to E 



Lubricating oil 6. . . 



Cod-liver oil 



Oil of pine needles. 



Oil of juniper 



Rape-seed oil 



Raw linseed oil. .. . 

 Lubricating oil i . . . 



Peanut oil 



Knochen oil 



Lubricating oil 2 . . . 



Wood creosote 



Olive oil 



Acetone 



Ether 



Gasoline 



Benzyl alcohol 



Chlorbenzene 



Nitroxylene 



Oil of verbena 



Oil of camphor 



Oil of lemon 



Oil of citronella 



Oil of lavender 



Oil of sassafras 



Oil of eucalyptus . . 



Oil of bergamot 



Oil of hemlock 



Oil of tansy 



Oil of mustard 



Red oil 



Coal-tar creosote. . . . 



Cottonseed oil 



Oil of turpentine. .. 

 Carbon bisulphid. .. 



Xylene 



Chloroform 



Chlorpicrin 



Petroleum ether. . . . 



Penetra- 

 tion." 



D to E 



Dto E 



E 



E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 E 

 EtoF 

 E to F 

 EtoF 

 EtoF 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 

 F 



" See figure i for explanation of letters. 



