PHILHYDRIDA. 



99 



back : the posterior legs in the typical families formed for swimming, but in the 

 others gressorial : the tibiae spinose, or simple : and the tarsi with the number 

 of articulations various. 



Notwithstanding the apparent discrepancy of structure among 

 the insects of this group, the latter, in their perfect state, appear 

 destined to cleanse the surface of nature from the decayed remains 

 of vegetable matter, as those of the following subsections do from 

 animal impurities ; though the typical family, in the larva state, are 

 decidedly carnivorous, and feed upon living aquatic mollusca, while 

 the conterminous group of Anisotomidse subsist chiefly upon fungi, 

 and the families of Parnidse and Heteroceridse are supposed to 

 devour animal substances alone. 



The insects of the typical family reside, in their first and final 

 states, in the water, and swim well; whereas those of the four 

 families preceding them generally prefer the banks, and may be 

 said rather to walk in the water than swim : the succeeding insects 

 frequent damp pastures, burrowing, by means of their spinous 

 tibise, into their pabulum, the dung of herbivorous mammalia, as 

 the Anisotomidse do into fungi; and thus resemble the Hetero- 

 ceridse, which also burrow by similar means. 



It has ever appeared extraordinary to me that Latreille and 

 others should have separated the insects of this group, by the inter- 

 vention of totally dissimilar objects, from the Hydradephaga, with 

 which they are evidently so intimately connected in habit : it there- 

 fore afforded me great satisfaction to find that the views of the 

 learned author of Annulosa Javanica corresponded so nearly with 

 my own on this point ; though I fear that my limited knowledge of 

 exotic forms may cause me to do violence to nature by proposing 

 the following arrangement of the indigenous families contained in 

 this subsection : 



Antennae - 



f haud serratse, ( moniliformes : 

 | sagpissime < 

 crassiores ^ ( filiformes : . 



| plus minusve ser- ( 4-articulati : 

 L rata? : Tarsi < 



I 5-articulati : 



^clavatae : C minuto 

 Tarsi I 



articul 

 primo 



' J l 



longiori 



Mandibular C inermes : 

 ad apicem< 



C. bidentatae 



1C. Anisotomidje. 



12. LlMNIIDiE. 



10. HETEROCERIDiE. 



11. Parnid^e. 



13. HELOPHOIuniE. 



14. HYDItOrHILIDiE. 



15. SrH/ERIDIID^E. 



II 2 



