THE SORGHUM MIDGE. 



51 



eight or ten stages of the midge against one ovary, all the stages rang- 

 ing from unhatched eggs to fully developed pupae, showing that egg 

 deposition is kept up until the hardening of the glumes at the apex 

 checks oviposition. 



Another important phase of egg deposition, which accounts for the 

 irregular emergence of the adults from a head, is that of the long 

 period during which a head is in condition to receive the eggs of the 

 midge. As has already been pointed out, oviposition may continue 

 for several days; this in itself gives rise to a 

 iarge number of midge forms of different stages 

 of growth on a single ovary. 



Again, oviposition continues upon a head 

 from the time the first spikelets are visible 

 through the opening sheath until after the head 

 is entirely exposed. Figure 27 represents four 

 stages of development of the head. a About 

 four days are required for the head to com- 

 pletely emerge, during which time the seed 

 have been infested by the midge as fast as they 

 were accessible to her ovipositor. 



LOCATION OF THE EGG. 



The location of the egg (fig. 28) varies, inas- 

 much as the condition of the glumes varies at 

 different stages of development, and conse- 

 quently a female ovipositing just before the 

 glumes close would not place her egg as far 

 down as the female ovipositing immediately 

 after the shedding of the blooms. Generally 

 speaking, the eggs are found near the apex of* 

 the ovary, but the writer has found them 

 located in practically every part of the inner 

 seed structure. It is therefore dependent upon 

 the stage of seed development as to where the 

 egg will be found. If infested during the flowering stage, the female 

 usually inserts her ovipositor between the first and second inner 

 glumes, and in such cases the egg will be generally found somewhere 

 near the apex of the ovary sticking to one of the glumes. In one 

 instance, at San Antonio, Tex., the writer observed females ovi- 

 positing hi glumes which had shed the flower and the apices of which 

 were too hard to admit of oviposition at that point. In this case 

 the females were observed to crawl over the glumes and then 

 insert the ovipositor into the crevice formed by the first outer glume 



a Fig. 27, b and c, are not normal, owing to the drying of the material before the 

 drawings could be made. 



Pig. 28.— Sectional views of 

 the sorghum seed during the 

 flowering stage: a, First 

 outer glume; 6, second outer 

 glume; c, inner glume; d, 

 second inner glume; c , lodi- 

 cules. X's indicate points 

 at which eggs of the sor- 

 ghum midge are commonly 

 found. (Original.) 



