OBSERVATIONS ON THE CHANGES IN THE HYPO- 



DERMIS AND CUTICULA OF COLEOPTERA 



DURING ECDYSIS. 



W. L. TOWER. 



The internal changes which occur during the periodic removal 

 and redevelopment of the chitinous portion of the integument of 

 insects are little understood and but few observations have been 

 made thereon. In this paper are given observations and conclu- 

 sions concerning some of the changes found in the integument 

 of Leptinotarsa decimlineata and Clirysobotliris femorata. These 

 two beetle larvae are good examples of two types of larvae, the 

 first living freely exposed upon their food plants and are typical 

 examples of those insect larvae which pass their lives upon plants 

 in exposed places and must go through ecdysis exposed, and the 

 second of larvae that live in burrows or cells, protected from ex- 

 ternal interference to a great degree. Corresponding to the differ- 

 ence in their habitats they show differences in the internal changes 

 accompanying ecdysis. 



The life of an insect larva is made up of a series of instars or 

 stages, each of which represents a very precise cycle of develop- 

 ment and physiological activities. These cycles of changes are 

 of interest and serve to give a good basis for the orientation of 

 the changes which I am about to describe as accompanying 

 ecdysis. The changes within a single cycle are given in the 

 tabulated form on page 177. 



Each larval stage properly begins with the period of growth 

 following the reconstruction period of the preceding ecdysis and 

 ends with the end of the next reconstruction period. Looked at 

 from the exterior the stages extend from ecdysis to ecdysis, but 

 as shown in the above table the period of exuviation is the middle 

 one of the short and rapidly passed over periods in which the 

 process of ecdysis is begun, achieved and the animal recovers 

 from the effects thereof. The changes with which this paper 

 deals are confined largely to the last three periods in the cycle. 



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