40 R. W. CROSSKEY 



pophyses produced into slender curled processes (Text-fig. 159). Scutum pale 

 greyish with dark lyrate pattern (Text-fig. 72) WILHELMIA Enderlein (p. 94) 



- Claws with very large basal tooth (Text-fig. 79). Pleural membrane bare. Gona- 



pophyses simple truncate lobes (Text-fig. 156). Scutum without pattern 



EUSIMULIUM Roubaud (p. 56) 



15 Pleural membrane bare. Claws simple . SIMULIUM Latreille s. str. (p. no) 



- Pleural membrane haired. Claws with very small basal tooth (Text-figs. 85, 86) . 16 



16 Scutum pale greyish with three broad longitudinal brown or blackish vittae (Text- 



fig. 73). Fore tarsus slender, basitarsus 7-8 times as long as its greatest breadth 

 (Text-fig. 85). Abdomen with three lines of dark spots on pale greyish ground 



TETISIMULIUM Rubzov (p. 104) 



- Scutum blackish with silvery greyish pattern anteriorly (Text-fig. 74). Fore tarsus 



dilated, basitarsus 4-5 times as long as its greatest breadth (Text-fig. 86). Abdo- 

 men dull blackish basally and shining black on tergites 6-8, not maculate 



ODAGMIA Enderlein (p. 107) 



Pupae 



1 Forms from Ethiopian or Malagasy Regions ....... 2 



- Forms from North Africa and Canary Islands . . . . . . . 13 



2 Pupae attached to mayfly nymphs*. Cocoon often covering only the pupal abdomen. 



Abdominal onchotaxy sometimes aberrant (Text-figs. 170, 173) 



PHORETOMYIA sgen. n. (p. 79) 



- Pupae not attached to mayfly nymphs. Cocoon not reduced (except in gyas from 



Madagascar). Abdominal onchotaxy normal (except in Dexomyia from St. 

 Helena) ............. 3 



3 Pupae attached to river-crabs. Gill with eight long slender filaments, usually 



longer than pupal body, arranged 3 + 3 + 2 (Text-fig. 195) 



LEWISELLUM sgen. n. (p. 76) 



- Pupae not attached to crabs. If gill with eight filaments not of this form (except 



similar in some Meilloniellum, Text-fig. 193) ....... 4 



4 Abdominal segments 5-7 ventrally with aberrant onchotaxy (Text-fig. 323), each 



with irregular transverse row of many hooks (numbering variable from 6-24 on 

 each segment). Gill with four filaments as Text-fig. 322. [St. Helena Island 

 only] DEXOMYIA sgen. n. (p. 49) 



- Abdominal segments 5-7 ventrally with normal onchotaxy (Text-fig. 171), each with 



one pair of hooks on each side, those of segment 5 closer together than those on 6 

 and 7 (bovis-group without hooks or with only a single pair on segment 5). Gill 

 not as Text-fig. 322 ........... 5 



5 Gill trifid or bifid with flattened lanceolate, subcylindrical or subspherical branches 



directed forwards (Text-figs. 221, 222). Terminal abdominal tubercles pointed 

 thorn-like, directed backwards .... BYSSODON Enderlein (p. 44) 



- Gill not with this form. Terminal abdominal tubercles usually very blunt . . 6 



6 Abdominal segments 6-8 bare dorsally. Cocoon shoe-shaped, with well developed 



neck (except albivirgulatum with incomplete neck and gyas with reduced cocoon) . 7 



- Some or all of abdominal segments 6-8 (sometimes also 9) with well developed back- 



wardly directed spine-combs (Text-fig. 168). Cocoon simple and slipper-shaped 



(Text-fig. 164), rarely with weak neck . . . . . . . . n 



7 Gill with four filaments (Text-figs. 205, 206) . FREEMANELLUM sgen. n. (p. 92) 



- Gill with more than four filaments or branches ....... 8 



8 Gill filaments with sharp pointed blackened tips (Text-figs. 203, 204), of one type and 



numbering 8-19 ANASOLEN Enderlein (p. 88) 



- Gill filaments without sharp darkened tips ........ 9 



* or to river prawns, see Appendix 



