EXPERIMENT STATION BULLETINS. 597 



EXPLANATION OF PLATES. 



PLATE I. 



Fig. 1. Photograph of the last two ganglia of the nervous system 

 of a caterpillar that had been dipped into kerosene stained with Sudan 

 III. Note the tracheae filled with red oil (black in the photograph). 

 After two to three hours none of the colored oil had yet passed through 

 the walls of these tracheae. 



Fig. 2. Photomicrograph of a cross-section of the abdomen of a Wil- 

 low-aphid treated with Creolin emulsion containing Indigo Carmine. 

 Fixed with absolute alcohol containing a little picric acid. Note the 

 plug of Indigo Carmine in the trachea at "a." No Indigo Carmine 

 was found in the body except within the tracheae. 



Fig. 3. Photomicrograph of a cross-section of a white wood-boring 

 larva that had been first treated with HjS gas and then immediately 

 injected with hot alcoholic lead acetate solution. Black lead sulphide 

 precipitated. No stain was used on the section. 



Fig. 4. Photomicrograph ; cross-section of the thorax of a cabbage 

 worm (Pontia rapae). No insecticide used. Tissues fixed with hot 

 picric alcohol. Stained slightly with iron haematoxylin. 



Fig. 5. Photomicrograph, cross-section of the thorax of a cabbage 

 worm (P. rapae) through the wing buds. This larva had been soaked 

 three ihours in kerosene. It was then dropped into picric alcohol. 

 Stained slightly with iron haematoxylin. 



Note that the tissues are in same condition as' in Fig. 4. 



Fig. 6. Photomicrograph, cross-section abdomen of cabbage worm 

 (P. rapae). Kepresents the appearance of the tissues in a part of the 

 abdomen treated externally thirty hours with Creolin emulsion. The 

 free untreated part of the body was still able to move (alive) at the 

 end of the period. Dropped into picric alcohol. Stained slightly with 

 iron haematoxylin. 



PLATE II. 



Fig. 1. Photograph of a (protected from rain) scale of Aspidiotus 

 {Chrysoynpphalus) ficus on orange; showing the white salts that stooled 

 up in three to four weeks after treatment with a solution of lime-sul- 

 phur. 



Fig. 2. Photomicrograph, cross-section of a flat wood-boring larva 

 placed in air containing a small percentage of H, S gas for two hours ; 

 then injected at once with alcoholic lead acetate as in case of figure 3, 

 Plate 1. 



Fig. 3. Photograph of A. ficus, on orange made seven days after treat- 

 ment with lime-sulphur. The dark portion along both margins of the 

 abdomen had blackened in this manner from decay. This portion had 

 been wet with the lime-sulphur, and it showed decay before the rest of 

 the body. 



Fig. 4. Photograph, Aspidiotus {Chrysomphalus) ficus six hours after 

 treatment with lime-sulphur. Shows how the wax on the margin of 

 the scale became softened and would sometimes stick to the pygidium 

 so as to pull out into a long thread. 



