DIPTERA. 327 



larvae inhabit cow-dung, earth, and dung'-hills, and have little ranges 

 of hairs on their annuli. Their pupae are not enclosed in cocoons *. 



AspisTEs, Hoff., Meig. 

 The only Insects of this division which have but eight joints in 

 the antennae, the last forming an ovoid club f. 



All the following Diptera, a small number excepted, have their 

 antennae composed of three joints, the first of which is so short, that 

 it may be excluded from the supputation ; the last is annulated trans- 

 versely, but without distinct divisions. It is frequently accompanied 

 with a seta, usually lateral, and situated on the summit in others, 

 presenting two joints at base, sometimes simple, and sometimes 

 silky. When this seta is terminal, it frequently happens that its 

 length diminishes and its thickness increases, so that it has the form 

 of a stilet. Although this piece may be considered as a continuation 

 of the antennoe, yet as it is separated from them, and appears to con- 

 stitute an appendage, to deviate from the course generally adopted, 

 by adding to the ordinary number of the antennoe those of the seta, 

 would only disturb the harmony of our nomenclature. The palpi 

 never have more than tAVO joints. 



Some, a few excepted, whose larva; divest themselves of their skin 

 previous to becoming pupae, always have a sucker composed of six 

 or four pieces ; the proboscis, or at least its extremity, that is to say, 

 its lips, is ahvays salient. The palpi, when they exist, are exterior, 

 and inserted near the margin of the oval cavity, close to which arises 

 the sucker. 



The larviB, even of those in Avhich the skin forms a cocoon for the 

 pupa (^S I ratio mi a), retain their primitive form. 



This subdivision will comprise three families. 



FAMILY ir. 



T A N Y S T O M A. 



The Diptera of this family are distinguished from those of the 

 tAvo following ones by the last joint of the antennae, which, exclusive 

 of the seta which may terminate it, presents no transverse division- 

 the sucker is com])osed of four pieces. 



Their larvae resemble long and almost cylindrical worms, with a 

 constant and squamous head, always provided with hooks or retractile 



* See Meigcn. 

 t Idem. 



