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 closing of the glumes at the apex makes 

 oviposition impossible. 



Another important phase of egg deposition, which accounts for the 

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

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

 the midge. As has already been pointed out, oviposition may con- 

 tinue from the time the seed glumes are sufficiently open until they 

 are closed; this in itself gives rise to a large 

 number of midge forms of different stages of 

 growth within a single seed. 



Again, oviposition continues upon a seed head 

 from the time the first seed are visible through 

 the opening sheath until after the head is 

 entirely exposed. Figure 27 represents four 

 stages of development of the seed head. About 

 four da}^s are required for the sheath to com- 

 pletely unfurl, 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 structure of the seed glumes varies 

 at different stages of development, and conse- 

 quently a female ovipositing within a seed just 

 before the glumes close would not place her egg 

 as far down as the female ovipositing immedi- 

 ately after the shedding of the blooms. Gener- 

 ally 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 two outer glumes and the 

 flowering glume, 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 

 ovipositing in seed which had shed the flower and the apices of which 

 were too tightly closed to admit of oviposition at that point. In 

 this case the females were observed to crawl over the seed and then 

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



Fig. 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; e,lodi- 

 cules. X's indicate points 

 at which eggs of the sor- 

 ghum midge are commonly 

 found. (Original.) 



