MAY-FLIES. 35 



DELEATIDIUM LILLII. 



Deleatidiicm lillii, Eaton, Trans. Ent. Soc. Lond., 

 1899, p. 289, pi. x., fig. 4. 



This little May-fly has occurred at Wellington and at 

 Dunedin. It is probably a common and generally dis- 

 tributed species. 



" Sub-imago (in fluid). — Wings uniformly light grey with opaque neura- 

 tion. Setae grey ; their joinings towards their tips evenly defined. 



"Imago (dried). — $ body pitch-brown, the thorax polished above. 

 Femora and fore-tibiae raw umber-brown ; fore-tarsus and hinder tibiae 

 lighter in tint; hinder tarsi somewhat of a sepia-grey throughout. Wings 

 vitreous with pitch-black neuration, except in the fore-wing, the finer cross- 

 veinlets of the marginal and sub-marginal areas that precede the pterostig- 

 matic region (which are deficient in colouring), and the roots of the stronger 

 nervures interior to the humeral cross-vein, which are raw umber-brown ; 

 the membrane at the extreme roots is almost imperceptibly tinted raw umber 

 or greenish. In the marginal area of the fore-wing, before the bulla, are 

 usually about 6 faint cross-veinlets, and beyond that 2-4 faint and 8-11 

 stronger veinlets, all simple. Setae light sepia-grey with blackish joinings, 

 of which some in the basal quarter are alternately distinct and faint. In 

 the abdomen, segments 3-6 are sometimes transparent and whitish to a 

 variable extent at the base. 



" ? very like the z , but the colouring at the fore- wing roots, interior to 

 the humeral cross-vein, is rather darker in tint. The marginal area of the 

 fore-wing contains about 3—5 faint cross-veinlets before the bulla and 2 

 faint and 13 stronger beyond that, all simple. Ventral lobe of the 

 ninth abdominal segment slightly (not deeply) emarginate, with acute 

 points " (Eaton). 



The transformations of this species closely resemble 

 those of Atalophlebia dentata. 



The length of the nymph when full grown is about g inch. The head 

 is large, somewhat square with rounded angles; the eyes are very pro- 

 minent ; the antennae are two and half times the length of the head. The 

 prothorax is very small ; the meso- and meta-thorax and the wing-pads are 

 large and well developed dark brownish-black, the wing-pads being almost 

 black. The abdomen is rather narrow and tapering, dull brown ; there are 

 two pale spots on segments 2, 3, and 4. The gills are acutely oval, single 

 with a central trachea emitting numerous branches. The anal setae are about 

 the same length as the entire insect. Younger larvae are semi-transparent 

 with numerous fine black markings. 



The perfect insect appears from October till January, 

 and is often found in enormous numbers flying over 

 streams and rivers at evening dusk. 



Genus COLOBUTUSCUS, Eaton (1887). 



Imago. — Legs all functional; hind-tibia longer than the femur or the 

 tarsus; tarsi 5-jointed, the fifth joint rather indistinct; first joint of the 

 hind-tarsus shorter than the second ; ungues in all the tarsi dissimilar. 

 Posterior wings well developed, oblong-oval, with the dilatation of the mar- 



