174 Annals Entomological Society of America [Vol. XIII, 



6. THE LIFE CYCLE OF THE COLEOPTERA 

 (Including the Strepsiptera). 



Royal N. Chapman, University of Minnesota. 



The magnitude of variations in the life cycle and form 

 changes which are met with when the Coleoptera and the 

 Strepsiptera are considered as a group are hardly exceeded 

 by any other group of insects. When we remember that there 

 are now considered to be more than one hundred families of 

 Coleoptera containing, in all, over one hundred and fifty 

 thousand species, it is not surprising that there is a great amount 

 of variation. 



Some of the standard works on the Coleoptera might lead 

 one to believe that beetles have no larval or pupal stages, 

 for they are not mentioned. When Buetenmuller published his 

 catalogue of the described transformations in 1891, the eggs 

 had been described for 52 species, the larvae for 368, and the 

 pupae for 96 species in North America. While a considerable 

 amount of progress has been made since that time it has been 

 only during recent years that attempts have been made to 

 correlate the knowledge of the transformations of even the 

 smaller groups. 



It is difficult to obtain accurate information with regard to 

 the various life cycles, especially with regard to the conditions 

 which cause variations in the duration of the various stages. 

 The data on which this paper is based have been taken in part 

 from statements in literature which seem to be dependable, 

 and in part from original experimental evidence. 



The type forms of the various stages of the life cycle are 

 subject to great variation throughout the group. The majority 

 gf the eggs are laid singly and unprotected, but the hydrophylid 

 eggs are in covered cases and some of the Carabidas deposit their 

 eggs in, cases constructed of mud. The egg stage is eliminated 

 among at least some of the Strepsiptera which are viviparous. 



The commonest larval form. is campodiform or cruciform, 

 being elongate and possessing thoracic legs, but all types of 

 larvae are represented. The generalized carabid larvae are 



