48 



CEREAL AND FORAGE INSECTS. 

 Table II. — Measurements of larvae of the sorghum midge. 



Larva No.— 



Length. 



Breadth. 



Larva No.— 



Length. 



Breadth. 



1.. 



Milli- 

 meters. 

 0.15 

 . 1804 

 .28 

 .329 

 .493 

 .573 



Milli- 

 meters. 

 0.075 

 .082 

 .082 

 .12 

 .141 

 .25 





Milli- 

 meters. 

 0.6 

 .89 ■ 

 .903 

 1.0 

 1.5 



Milli- 

 meters. 

 0.3 



2 



8 



35 



3 



9 



.35 



4 



5 



6 



10 



11 



.492 

 . 5 



While the above examinations do not refer to larvae of the same 



generation, they serve to illustrate the gradual growth from the 



time of hatching until just before transformation into pup as. These 



figures can safely be taken as representative of the measurements 



-of a single larva from date of hatching until 



full grown. In this instance the larval stage 



covers eleven days. 



THE PUPA. 



Fig. 26. — The sorghum midge: 

 "Cocooned larvae," the hi- 

 bernating form of the midge. 

 Much enlarged. (Original.) 



(Fig. 25,/.) 



When newly formed the pupa is uniformly 

 deep red in color, while just before emergence 

 of the adult the head and appendages turn 

 dark and finally black, while the abdomen 

 remains a deep red. There is often a delicate 

 cocoon surrounding the pupa before the latter 

 has worked its way to the apex of the spikelet for the emergence of 

 the adult. It is evident that such are found upon those pupae 

 derived from " cocooned larvae." This thin covering is very loosely 

 attached to the pupa and has never been found by the writer after 

 the pupa has left its initial position alongside the ovary. 



THE "COCOONED LARVA." 



(Fig. 26.) 



The "cocooned larva" is closely allied in structure and function to 

 the " flaxseed " of the Hessian fly. The delicate envelope is somewhat 

 elliptical in shape, quite flat, and of a muddy-brown color. It is found 

 close against the ovary itself within the delicate palet. Examined 

 through the microscope the envelope is semitransparent, containing 

 a larva about two-thirds grown and surrounded by a clear proto- 

 plasmic fluid. In this form the segmentation of the larvae is dis- 

 cernible, yet the structures seem faintly outlined and embryonic 

 in contrast to the naked normal larva. The function of the "co- 

 cooned larva" is to perpetuate the species over winter and is the 



