582 Dr. r>. Keilin on the 



living larva between the slide and a cover-glass, fonr bifid 

 transparent papillse make tlieir appearance from the anal 

 opening. When completely everted from the larval body 

 these papillse are seen to arise in pairs from two large 

 transparent vesicular bodies (PI. XX. fig. 14). These pro- 

 trnsible papillse (r/7.) are homologous with the rectal gills of 

 other Chironomid larvae. In most cases when the larvpe are 

 under observation, the rectal gills and the 6 pairs of hooks 

 are retracted inside the body of the larva. 



(d) Ititernal Organs. 



Alimentary Canal. — The pharynx is followed by the oeso- 

 phagus, which in the 3rd thoracic segment enters the 

 proventriculus. The mid-gut is a straigl)t cylindrical tube. 

 The two pairs of Malpighiau tubes arise at the junction of 

 mid- and hind-gut, the anterior pair being long while the 

 posterior pair is short. There is no intestinal coeca. The 

 salivary glands are well developed and extend from the 2nd 

 thoracic to the 6tli abdominal segment. The cells of these 

 glands sometimes show in their protoplasm needle-shaped 

 crystals, the nature of which I was unable to determine. 



The nerve system is composed of cerebral ganglia and 10 

 pairs of ganglia of the ventral chain, the last being double 

 and composed of two pairs (10th and 11th) fused together. 



The respiratory system is apneustic, with the tracheae and 

 especially the peripheral thoracic and the rectal well 

 developed. The remains of the 10 pairs of non-functional 

 spiracles are connected with the main tracheal trunks by 

 means of 10 pairs of filaments without any lumen. The 

 vestiges of spiracles are found in the pro- and metathoracic 

 and in the 8 abdominal segments. 



The fat-body, in addition to the peripheral sub-hypodermic 

 pigmented cells, comprises two longitudinal perivisceral 

 bodies devoid of brownish excretory granules. 



IV. Pupa. 



The pupa is completely free from the larval cuticle. It is 

 2"3 mm. long and of a brown colovir. It becomes dark, 

 almost black, when the imago is almost completely formed, 

 but this coloration is due to the early pigmentation of the 

 hairs of the imago seen through the transparent cuticle of 

 the pupa. 



The main characters of the pupa, which are of taxonomic 

 value, ai'e shown in figs. 15 to 21 (PI. XX.). Each wing of 

 the pupa bears near its terminal portion a small knob-like 

 protuberance {p.w., fig. 15, PI. XX.). Two pairs of legs are 



