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. Late in summer emer- 

 gence of these parasites and midges from infested heads is approxi- 

 mately in the proportion of 6 of the former to 1 of the latter. 



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 spinedAmaranthus (Amaranihus 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.— Aprostocctus diplosidis: Female. Greatly FlG.30. — A prostocetusdiplosidis: Male, 



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



their point of attack. These beetles were afterwards determined as 

 Disonyclia collataFab. and D. glabrataF&b. 



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 spikelet, the head 

 toward the apex of the latter, and arching the abdomen drives the 

 ovipositor through one of the glumes to the interior. 



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 



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

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



