1862.] 158 



will, be modified by future research; but the only way to arrive at their 

 improvement, is to establish a basis to start from. 



I. LARVA. 



The general characters of the larva) of Mycetophllidae,, known to me, 

 may be set down thus :- 



A distinct horny head ; a fleshy lahram, encased in a liornij frame ; 

 horny, flat, lameUiform mandib/es, indented on the inside; maxillse with 

 a, large coriaceous inner lohe, and a horny outside piece, with a circnlar 

 excision at the tij) ; labium horny, small, almost rudimentary ; body 

 fleshy, u'ith eight pairs of stigmata. 



I. The head consists of a more or less strong horny shell ; it is strongest 

 in Bolttophila and softest in Sciophila ; it is open anteriorly and poste- 

 riorly, the anterior opening containing the trophi, the posterior one form- 

 ing the connection with the first thoracic segment. 



Viewed from above, the heads of the larvae show the following differ- 

 ences: Ist.-In the form, which is sometimes cordiform (fig. 2, Myc. sig- 

 nata) ; sometimes almost square (fig. 4, Sciara) ; or broad and rounded 

 (fig. 9, Bolttophila). The head of Sciophila, as well as that of the 

 larva which I suppose to belong to Leja, are more elongated than the 

 others (figs. 6 and 7). 2d.-In the outline of the posterior (occipital) 

 margin; in Mycetophila and Sciara, it is more or less emarginated in the 

 middle (figs. 2 and 4, <.); the same is the case with the four larvae of 

 Mycetophik* and with Cordyla crassipalpa, and Sciara ingeniia, all de- 

 scribed by Dufour; this emargination is sometimes in the middle of a 

 produced lobe (fig. 10,^/.), or of a lobe formed by two lateral emarginations, 

 although not produced beyond the lateral parts of this margin (fig. 10, b) ; 

 sometimes the lobe is hardly perceptible (fig. 10, <■.) ; in some larvae, as, 

 for instance, that of Myc. signata, there is a distinct notch on each side of 

 the lobe (fig. 2,^), formed by a fold of the horny substance. In Bolito- 

 phila (fig. 9) and Sciop)hila (fig. 6) the posterior mai'gin is not, or is almost 

 imperceptibly emarginated and not produced. 3d.-The direction of the 

 occipital lines, two slender, pellucid lines, beginning at the interval be- 

 tween the mouth and the antenna and running towards the posterior mar- 

 gin. They converge towards the middle of this margin in Mycet. signata, 

 Sciophila limbatella and in all Sciarse which came under my examina- 

 tion ; sometimes they are nearly straight (fig. 2 and 6, /"), sometimes 

 undulated and angular (fig. 4,/). They are not convergent, and reach 

 the posterior margin at two distant points in Bolitophila (fig. 16). 



Viewed from beneath, the horny shell of the head also shows some 



