56 CEREAL AND FORAGE INSECTS. 



summer, when the second and third crops of sorghum are heading. 

 These crops are found to mature upward of 90 per cent of sound seed, 

 while the earlier crops are a total failure. During the latter part of 

 the summer these parasites often outnumber the emerging midges 

 5 to 6. 



Only one observation has been recorded as to the feeding habit, 

 of this parasite. On August 1, 1908, the writer observed the parasites 

 clustering upon the leaves of the spined Amaranthus (Amaranthus spi- 

 nosus) , commonly known as " careless weed." Investigation revealed 

 that these followed in the wake of some leaf-eating beetles which 

 abraded the leaves, from the torn edges of which the juice oozed. 

 This the parasites fed upon, following the leaf eaters as they changed 



Fig. 29.— Aprostocetus diplosidis: Female. Greatly Fig. 30.— A prostocetus diplosidis: Male, 



enlarged. (Original.) Greatly enlarged. (Original.) 



their point of attack. These beetles were afterwards determined as 

 DisonychacollataF&b. and D. glabrataYab. 



The distribution of Aprostocetus diplosidis is generally the same 

 as that of the sorghum midge, although in some sections where the 

 latter abounds the parasite is not found. a 



The method of parasitism can be seen readily in the field. The 

 parasite crawls slowly over the infested heads and then, apparently 

 locating a larva, takes up a position upon the seed head toward the 

 apex of the latter and arching the abdomen drives the ovipositor 

 through one of the glumes to the interior of the seed. 



The species of Tetrastichus referred to, while not proved to be pri- 

 mary in conjunction with Aprostocetus diplosidis, is certainly primary 

 upon the midge in some instances. During the early part of the 

 season, when only Johnson grass is available as a host for the midge 



a Fayetteville, Ark., and Neodesha, Kans., have not been recorded as sections 

 abounding in the parasite, although the sorghum midge occurs quite abundantly. 



