34 BRITISH FLIES 



^. The upper in-grown [or internal] part of the head-capsule resolved into rods, 

 cleft or forming a flat cleft-like plate. The rods sometimes only thickened 

 ribs of thin transparent narrow chitinous plates. (c) Bomhylimorpha. 



1. Hind stigma-plates large, round, terminal and free. Upper jaw-capsule 



rather large and free, lunulate ; the in-grown part short, forked, narrow. 

 Mouth-parts of the mature larva rudimentary. F. Acroceridce. 



2. Hind stigma-plates large, round, terminal, placed in a transverse cleft enclosed 



by lips. Upper jaws hooked, with a straight acumen between them. 



Lower jaAv rudimentary. LTpper jaw-capsule with the free part very 



short, the internal part long. F. JVemestrinidce. 



tt Hinder stigmata ])laced on a band or segment before the last, or even on the 



third from the end, usually small. 



Group Ueterodactyla (Tribus Orthocera Schin., pp.). 

 Hinder stigmata placed on the penultimate segment, or on a flat dorsal band 

 before the last segment. Intermediate segments few or none. 



(a) Procephaki {Mydaidcc, Asilidce, Bomhi/Jidcf). 

 Hinder stigmata placed sideways on the third segment from the end. Six or more 

 intercalated segments (see fig, 65). 



{h) Folytonxa {Therevidie, Sceno2nmdce). 



(III.) Tribus Orthogenya. 



Eleven to twelve obvious segments after the divisions bearing the antenniP and 

 mouth -parts. 



Jaw-capsule developed at the free end only dorsally as a lunate plate, the in- 

 grown end forming large plates or fish-bone structures. The chitinous skeleton of 

 the lower lip formed of two arched bands standing vertical and contiguous in an 

 angle anteriorly, which bear a certain resemblance in their union to the lower 

 jawbones of mammalia. Hinder stigmata placed terminally on the last segment, 

 sometimes on pi'olongations. Empidoe, Dolichopoda. 



The preceding table is largely taxonomic and is not very suitable for determining 

 larvae. Brauer (no doubt feeling this) has added in a footnote a more simple table 

 for the larva of the Beachycera, as follows : 



" For determination, without reference to affinities, the larvae of Orthoeehapha 

 Beachyceea may be tabled as follows : 



I. Larvpe with a terminal fissure for the hind spiracles, in which the two main 



tracheal trunks open near to one another. 



(a) The fissure horizontal or transverse. Head-capsule not retractile. 



Strationnyiidxie. 



(b) The fissure vertical. Head-capsule retractile. Tabnm'dce. 



II. Larva? with seixxrated terminal spiracle-tul)es or plates. 



L Hinder spiracles placed on last segment. 



(a) Labial plate and rods behind it flat in one plane, or wanting, or soldered 

 with the capsule. 

 a Head-capsule not retractile, stigma-iilates projecting. Xylophagidce. 

 aa Head-capsule retractile. 



/3 Only ten segments behind the one that bears the antennae. 



Aa'optera [ = Loiichopteridce], 

 /3/3 Eleven or twelve segments behind the one that bears the antennae. 

 7 Head-capsule long, in larger part internal, pyriform. 



Leptidce, Acautfiomerida;. 

 77 Head-capsule short, the internal part flat or divided into rods. 



Spiracles in a fissure, Kemestrinidtt. 

 Spiracles free, Acroceridce. 

 (b) Labial plates and rods meeting angularly, in jtrofile appearing bent. 



DoUchopndce and Empidce. 



2. Hinder spiracles placed anterior to the last segment. 



a. On the penultimate segment. Asilidce, Bombyliidw, Mydaidoe. 



aa. On the antepenultimate segment. Therevidct, Scenopinidee." 



