THE SORGHUM MIDGE. 



43 



tory methods were employed to gel at the more obscure phases of the 

 problem. 



In Louisiana it was found that, owing to the excessive humidity, 

 infested sorghum heads when brought into the laboratory from the 



held almost invariably molded and rotted before observations upon 



the emergence of the adults could be made, and. furthermore, such 



conditions would not yield true 



results. For this reason, then — 



and the same applies to Texi 



all records ( f life history were 



made in the field upon growing 



heads and subject to absolutely 



normal conditions. 



In brief, the method employed 

 in the study of the various forms 

 of the midge was to select a num- 

 ber of sorghum stalks in the field 

 whose seed heads had not broken 

 the boot or protecting sheath 

 and which were therefore not in- 

 fested by the midge. Over these 

 unbroken heads were placed 

 waterproof paper bags, the bot- 

 toms o( which were gathered 

 securely about the stalks well 

 below the head and securely tied 

 with string, to which tags were at- 

 tached. These bags were allowed 

 to remain over the unopened 

 heads until by observation the 

 latter had broken the sheath 

 and the seed were in a condition 

 to receive an infestation by the 

 midge. Then they were removed 

 from the heads, and these were 

 watched until females were actu- 

 ally seen to oviposit within the 

 seed glumes. When the natural 

 infestation was well under way a 

 note was made upon the small tag attached to the stalk below 

 the head, giving the date and the hour of the first egg deposition. 

 fig. H.) 



At various times these seed heads were cut and dissected in the 

 laboratory and the oldest form of the midge found therein recorded, 

 3217ft— Bull. B5, pi I -10 2 



—hum head, bagged and 

 after natural infestation by the sorghum midge. 

 This method is also practical for protecting 

 the field from damage by the midge. (.Original.) 



