406 



of a species of Cecidomyia "develops in its interior a brood of larvae 

 of a like structure with itself," these again giving birth to other 

 larvae in succession. It is thought by Herbert Spencer that, as 

 in the case of the Aphides, the fact may be explained by the 

 circumstance of there being " abundant food combined with low 

 expenditure." The larvae of the Cecidomyia " are found in such 

 habitats as the refuse of beet-root sugar factories, where each of 

 them has a practically unlimited supply of sustenance imbedding 

 it on all sides." * If this be the explanation, it seems not at all 

 unlikely that internal metagenesis may prevail in the case of 

 many other insects, the larvae of which are similarly circumstanced, 

 and such cases should be diligently sought for by the local 

 entomologist and carefully looked into. 



Sir John Lubbock considers this case of the larvae of the 

 Cecidomyia as " a distinct case of alternation of generations, as 

 characterized by Steenstrup." And he thinks "probably other 

 cases will be discovered in which insects, undeniably in the larval 

 state, will be found to be fertile. It even seems to him possible, 

 if not probable, that some larvae which do not now breed, in the 

 course of ages may come to do so." t 



And there are yet other cases of abnormal reproduction which 

 have been noticed of late years equally at variance with our 

 preconceived ideas on the subject. Two instances are on record of 

 viviparous insects ; i.e., insects in the perfect state, instead of 

 depositing eggs, producing living larvae. One of these is that of a 

 species of Tinea (Tinea vivipara) found in New South Wales. X 

 The other that of a small species of Staphytinus found in the nests 

 of the Termites, or white ants, in Brazil. § It is true these are 

 both cases of foreign insects, but there is no a priori reason why 



the occurrence of this phenomenon in moths and bees. In a recent work he 

 has recorded many new observations in support of " his position that not only 

 do unimpregnated eggs develop into perfect animals, but that such an event 

 is by no means an exceptional occurrence among certain groups, and has a 

 definitely-fixt'd and orderly recurrence amongst them." 



* Princ. of Biol., vol. 2, p. 467. t Linn. Trans., vol. xxv., p. 488. 



X Ent. Trans., 3rd Ser., vol. i., Proceed, p. 153. § Nature, vol. iii., 



p. 330. 



