178 PROCEEDINGS OF SOCIETIES. 



him injury, decimating his most precious crops, or deforming the pro- 

 duce of the orchard and the garden. 



Apart from its Economical bearing, the history of the development 

 of the Diptera has a further interest, as it exemplifies nearly the most 

 complete type of metamorphosis among the insect race, whether the 

 change of habits, or of form, be considered, with all the new organs and 

 faculties finally acquired, and the death-like slumber, — coffined, as it 

 were, in many instances, in the spoils of the gross body that existed 

 before that change, the last but one, — awaiting the moment when the 

 imprisoned tenant, ripe for new life, shall burst from its cerements, to 

 taste the freshness of a purer air, and revel in the untried delights of a 

 higher existence. 



If enough has been ascertained of the transformations of the Diptera, 

 to afford such a general sketch of the aspect in which it meets our ob- 

 servation, yet we know too little, as yet, to satisfy either the purposes 

 of System, or the requisitions of Natural History in its larger sense. 

 The caterpillars of the Lepidoptera live comparatively in public ; even 

 the minute, hidden leaf-miners have been drawn out to light, for the 

 sake of their great relations, or for the beauty of their own last, perfect 

 garb. The Ephemera, the Mayflies, the Dragonnies, have early found 

 their historian. More slowly and laboriously the materials have been 

 accumulated for a history of Coleopterous larvae also, which Chapuis and 

 Candeze have condensed and methodized in their useful Catalogue ; while 

 we are yet far indeed from the prospect of a similar acquisition to the 

 study of the Diptera. That minimum development of specific organs of 

 sense or motion, which characterizes the larvae of this order generally, 

 seems to narrow the base on which a systematic arrangement of them 

 may be reared ; and their most conspicuous outward differences of general 

 form and peculiar appendages stand in a more intimate relation to the 

 particular mode of life and medium of habitation, than to the zoological 

 characters which determine the systematic place of the perfect insect. 

 A closer study will doubtless guide us hereafter to the appreciation of 

 other external marks of distinction and affinity, at present overlooked 

 or not understood. Still it seems probable that, for a long time, we 

 shall not be able to dispense with considerations of the internal anatomy 

 and physiological functions in the characteristic and arrangement of the 

 Dipterous larvae. In the list I have compiled of British species, the 

 earlier history of which is known in some degree (with other European 

 species which may serve to illustrate the indigenous genera), I have 

 aspired to nothing more than to furnish an index, carried forward by 

 additions subsequent to the date of Mr. Westwood's " Modern Classifi- 

 cation of Insects," but without the aid of descriptions and figures, such 

 as he has given in that very useful work, — a collection which is indeed 

 indispensable to the student of the Diptera, as I know of no other work 

 in which he can look, with any hope of satisfaction, for similar condensed 

 and digested information. Much less shall I attempt to follow the prece- 

 dent of the excellent " Catalogue of Coleopterous Larvae" above referred to, 

 by extracting the full descriptions, or the essence of them, from the best 



