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trachea. The chitin-layer is continued by a firm layer of 

 densly conapressed and destroyed fat- cells. The larvæ 

 hibernaie in the second stage, develop in spring to the 

 third stage, pupate in the abdomen of the beetle, and the 

 imagos leave this through a hole in its posterior end. In 

 each beetle up to 7 parasites may be found. 



Octjptera brassicaria F. is parasitic on Üolycoris bnccarum 

 F. Its relation to the hemiptere agrees with what has 

 been described with regard to the Viviann, with the excep- 

 tion that there is no layer of destroyed fat- cells round the 

 larvæ (Fig. 10). The parasite hibernates in the second 

 stage; the boring out which takes place in June and July 

 does not kill the host. The pupation follows in the ground. 

 Only one parasite is present in each hemiptere. 



Explanation of the Plates. 



PL 1. 



Ptychomyin seleda Meig. 



Fig. 1. Transverse section of a larva of Hyponomeuta 

 euomjmella sometime after the boring in of a 

 Ptychomyia «e/ec^« -larva; the parasite is not shown. 

 ^^I\. æ. eggshell; ih. the hole through which the 

 parasite has penetrated into the host: k. chitinous 

 invagination of the host's cuticula which forms the 

 funnel; ki. lighter chitin on the outside of the 

 funnel; 1. leucocytes; s. the sac that surrounds 

 the parasite and which is formed of emptied fat- 

 cells; t. the alimentary canal of the host; uh. the 

 hole through which the parasite leaves the egg; ep. 

 the host's hypoderma; oc. the cuticula of the host. 



Fig. 2. The side of a hole through which the parasite has 

 penetrated into the host, shortly alter the penetration. 

 The letters as in fig. 1. i^^/i. 



