194 AN INTRODUCTION TO ENTOMOLOGY 



The reproduction of the sheep-tick, Melophagus ovinus, may be 

 taken as an illustration of this type of development ; this is described 

 in the discussion of the Hippoboscidas, the family to which this insect 

 belongs. 



The giving birth to old larva? is not restricted to the Pupipara. 

 Surgeon Bruce (quoted by Sharp, '99) has shown that the Tse-tse-fly, 

 Glossina morsitans, reproduces in this way, the young changing to 

 pupas immediately after birth. 



An intermediate type of development is illustrated by Hylemyia 

 strigosa, a dung-frequenting fly belonging to the Anthomyiidas. 

 This insect, according to Sharp ('99), produces living larvae, one at a 

 time. : 'These larvae are so large that it would be supposed they are 

 full-grown, but this is not the case, they are really only in the first 

 stage, an unusual amount of growth being accomplished in this 

 stadium." 



/. NEOTEINIA 



The persistence with adult animals of larval characteristics has 

 been termed neoteinia* or neotenia. When this term first came into 

 use it was applied to certain amphibians, as the axolotle, which retains 

 its gills after becoming sexually mature; but it is now used also in 

 entomology. 



The most familiar examples of neoteinic insects are the glow- 

 worms, which are the adult females of certain beetles, the complemen- 

 tal females of Termites, and the females of the Strepsiptera. 



II. THE DEVELOPMENT OF APPENDAGES 



In the preceding pages the more obvious of the changes in the 

 external form of the body during the metamorphosis of insects and 

 some deviations from the more common types of development have 

 been discussed. The changes in the form of the trunk that have been 

 described are those that can be seen without dissection; but it is 

 impracticable to limit a discussion of the development of the appen- 

 dages of the body in this way, for in the more specialized types of 

 metamorphosis a considerable part of the development of the appen- 

 dages takes place within the body -wall. 



*Neoteinia: neos (^os), youthful; tcinein (reiveiv), to stretch. 



