156 EEY. A. E. EATOX OX EECEXT EPHEMEBID.E OR MAYFLIES. 



BAETIS, Leach, 1815; 



Illustrations.— Adult (details), Pis. XVI. & XVII. 29 a-f, also LXIV. 9-20 ; (whole 

 figures) see citations, under Baetis, of Clo'e 'Siciet passim. Nymph, PI. XLIV. ; see also 

 Pictet, op. cit. pis. 34 & 36 (1843-5). 



Adnlt. — Hind Ming oblique, widened rapidly in front from the roots to the costal 

 projection, usually rather broad and obtusely ovate, but sometimes oblong or ovate- 

 lanceolate with the tip ellipsoidally rounded ; costal projection in general small and 

 acute, but in B. atrehai'mus suppressed ; neuration very sparse, comprising only 2 or 3 

 distinct longitudinal nervures (of which the intermediate is forked in some instances), 

 the great cross vein, and in certain species very scanty feeble traces of rudimentary 

 cross v.einlets or intercalar veinlets that are liable to much individual variation. Pore 

 wing [except B. Salvini, PL XVI. 29 a] devoid of colour ornamentation ; marginal and 

 submarginal areas [Avith the same exception] free from cross veinlets fi'om the great 

 cross vein to the bullae ; terminal margin beset with paired ru.dimentary intercalar 

 veinlets ; cross veinlets in the disk disposed mainly in two dislocated series between 

 the subcosta and the cubitus (5), and two, also dislocated, behind the latter nervure, 

 with occasional sparse indications, near the base and tip of the wing, of others irregular 

 and defective, aU at some distance from the terminal margin. Of the series in advance 

 of the cubitus, the innermost commences at the subcosta or radius shortly beyond the 

 buUfe and extends quite to the cubitus, if not farther, often blending with the outermost 

 of the posterior series ; the second series in advance of the cul^itus starts abreast of the 

 former just before the pterostigraatic dilatation of the marginal area, and terminates at 

 the hindermost of the sectorial iutercalars ; the defective third anterior series nearer 

 the apex of the wing is usually represented l^y only a single cross veinlet uniting the 

 shortest of the sectorial intercalars with the one immediately in front of it. Of the two 

 main series of cross veinlets posterior to the cubitus the outermost is the longest, ex- 

 tending most commonly from this nervure to the first axillar, but sometimes to the 

 second axillar ; between the cubitus and the pobrachial (7) nervure the cross veinlets 

 composing it are liable to displacement outwards so as to be nearly in even line with 

 the innermost of the anterior series, above described, rather than with the remainder of 

 their own series : the second of the series posterior to the cubitus is liable to a similar 

 dislocation outwards between the same two nervures, and to displacement inwards 

 posterior to the anal (8) nervure ; its first portion reaches from the pobrachial to the 

 cubitus [in B. Salvini it is prolonged to at least the sector (4)] somewhere near the 

 proximal extremity of the fifth sectorial intercalar ; its intermediate portion is a single 

 cross veinlet between the pobrachial and anal nervures, in a line with the junction of 

 the sector and cubitus ; its third portion lies nearer the wing-roots between the anal 

 and second axillar nervures ; sometimes a third posterior series is indicated by a few 

 cross veinlets quite close to the axilla, which commences at the anal nervure. Porceps- 

 limbs of 6 4-jointed; basal joint short and comj)act, considerably the stoutest, and 

 suddenly contracted towards the distal joining; second joint rather stout and usually 

 tapering gradually from the base ; third joint comparatively slender, subcylindrical, 



