INTRODUCTION. 5 



of the neighboring families is, that as far as known they are 

 nietapneustic, that is, they have a single pair of spiracles at the 

 anal end of the body. The genus Trichocera, anomalous in 

 many respects, is the only one, provided Mr. Perris' statements 

 are correct, which has two pairs of spiracles, a thoracic and an 

 anal one. A second characteristic peculiarity of these larvae is 

 the structure of the mentum, which consists of a horny plate, 

 pointed in front, and with several more or less deep indentations 

 on both sides of this central point. I found this organ in all the 

 larvae which I have dissected ; it is entirely different from the 

 corresponding organ in the larvae of the 3Iycetophilidse (compare 

 my description of these in the Proc. Entom. Soc. Phil. 1862, p. 

 151, Tab. I). 



The head of the larva is comparatively large, imbedded nearly 

 up to the mouth in the first thoracic segment ; it consists of a 

 horny shell, open on the under side and in front ; the parts of the 

 mouth are inserted in the latter opening. The comparatively 

 large labrum, lapping over the mouth when it is in motion, has 

 a rather complicated structure, partly horny, partly fleshy, vary- 

 ing in the different genera ; often, for instance in Tipula, with 

 bristles and microscopic hairs in front. The mandibles are horny, 

 very strong (not flat, as in the Mycetophilidse), generally bifid at 

 the tip and often with several indentations on the inner side. 

 The maxillae are likewise large and stout ; more or less fleshy on 

 the inside, but strengthened on the outside by horny plates ; they 

 have a short palpus on the outside and the usual lobe, coriaceous, 

 often provided with an entanglement of hairs and bristles, on the 

 inside. The mentum, already alluded to above, is a horny lamel 

 of variable structure ; in Tipula and Ctenophora I have found it 

 triangular in front, the sloping sides bearing several small inden- 

 tations ; in a larva of Limnobia this organ had five large teeth 

 in front. Under the mentum, inside of the buccal cavity, I have 

 perceived in the larvae of Tipula and Ctenophora another smaller, 

 rounded, horny lamel, with indentations on its anterior side. The 

 plane of this second lamel is parallel to that of the first, and it 

 may be seen moving up and down, when the mouth is in motion. 

 The antennae, placed on the sides of the mouth, consist of a 

 rounded, fleshy basal piece, and a cylindrical, horny shaft, ending 

 in one or several stout bristles. 



