466 



a. Megoiìerculata m. ^2, 



4. Ordnung: Pedipaipi Lati. 



5. - Araneae Sund. 



b. Cryptoperculata m.^^^ 



6. Ordnung: 3Ieridogastra Thor. ICryptosiemma Gnér. 

 B. Holotracheata m. 



a. Holosomata Pocock. 



T.Ordnung: Chelonef hi Thor. 

 S. - Opiliones Sund. 



9. - Acarina >Jitzscli. 



b. Mycetophora Pocock. 



10. Ordnung: Solifugae Sund. 

 Marburg, den 20. Februar 1902. 



2. Observations on the Structure of the Exuvial Glands and the Formation 

 of the Exuvial Fluid in Insects. 



By W.L. Tower. 



(With 8 figs.; 



eingeg. 22. Februar 1902. 



In Insects, the end of one developmental stage and the beginning 

 of another are marked by the casting of the cuticular covering, and of 

 the intima of all ducts and tracheae and of the alimentary canal. These 

 are then replaced by a fresh development of the cuticula over all the 

 hypodermal tissues thus laid bare. This process has been repeatedly 

 observed from the outside, and we know in detail the manner of the 

 casting and the time required to complete it in many insects. Of the 

 internal changes, however, which take place during ecdysis, we have 

 almost no mention, excepting a few scattered and incomplete accounts. 

 The observations which are recorded in this paper were made 

 upon larvae of the Chrysomelid beetle, Leptinotarsa decem-lineata Say. 



My material was killed in : 



Saturated Cor. Sub. (HgCl2) in 35^ alcohol . . . TOccm. 



Glacial Acetic Acid 30ccm. 



This was used for one minute or less at a temperature of 60° — 65°C. 

 and was followed by a solution of: 



Saturated Cor. Sub. (HgCia) in 35 X alcohol . . . 99ccm. 



Glacial Acetic Acid I com. 



42 Màyaç = groß, operculum = Deckel, wegen der großen Bauchplatte Ge- 

 nitalopercula) des 2. Mesosomalsegmentes, die die Geschlechtsausführungsgänge 

 nach außen bedeckt; y.Qimo; = verborgen, operculum, wegen des Fehlens der 

 großen Bauchplatte vVr der Geschlechtsöffnung. 



