125 



The appearance of a larv^a after the disease is well advanced is char- 

 acteristic. The body loses its firm consistency and becomes quite 

 flabby, while its color fades to a rather uniform greenish yellow. (See 

 PI. XIX, fig. 8.) The larva loses the power of coordinated move- 

 ment, only wriggling or twitching spasmodical^ when disturbed, and 

 soon begins to turn darker. Within a few hours after its death it 

 assumes a purplish black color, and the whole internal contents liquefy 

 more or less completely. When the skin is broken this liquid mass is 

 seen to have a distinct reddish tinge. 



Larvae living in a humid atmosphere seem to be more susceptible to 

 the disease. The following table, containing some of the more com- 

 plete records made during the course of the work, will give a general 

 idea as to the percentage of larvae destroyed by this disease: 



Table L. — Percentage oflarvx destroyed by bacterial disease. 



Date of col- 

 lection. 



Locality. 



Food plant. 



Number Per cent 

 collected, diseased. 



July 1,1903 

 Aug. 3,1903 

 Aug. 4,1903 

 Aug. 17,1903 

 May 28,1904 

 Aug. 20,1904 

 Aug. 25,1904 

 Aug. 30,1904 

 Sept. 24, 1904 

 Oct. 7, 1904 

 Oct. 24,1904 



Victoria, Tex 



Com 



do 



2-3 



Calvert Tex 



300 4A 



do 



do 





6 

 in 



do 



Alfalfa 



si 



Dallas, Tex 



56 , 10 



Paris Tex ... 



Cotton 



do 



184 i 49 



do : 



40 



12 



111 



17 



37 



5 



. ..do 



Corn 



17 



do 



do 



63 



do 



Alfalfa 



do 



12 



do 



29 











Averages: Corn, 18 per cent; cotton, 27 per cent; alfalfa, 17 per cent. 



The great discrepancies in the different lots are in large part due to 

 the fact that some counts were made by examining larva? freshly col- 

 lected, and others from larvae kept in the laboratory for a considerable 

 time, a few djdng each day. The large percentages indicated in some 

 of the columns, however, show plainly that under certain conditions a 

 great proportion may succumb to this malady. One unfortunate cir- 

 cumstance is the fact that it is nearly always the larger larv« which 

 are attacked. 



In the laboratory several cultures were made from a dried larva that 

 had died from bacterial disease. After five days all the cultures had 

 acquired a pinkish tinge, and each, when examined under the micro- 

 scope, yielded a ciliated organism of a bright crimson color, readih' 

 visible with a one-twelfth-inch oil-immersion lens, without staining. 

 Four health}^ worms were infected from the cultures by pressing the 

 head and mouth parts against the red gelatine. Of the larvae thus 

 infected, two died within two days with the symptoms of the bacterial 

 disease; one escaped, and the fourth, full-grown when infected, 

 pupated successfull3^ From one of the first cultures, two more were 

 then started and after six daj^s were characteristically red. These 



