of a Species of Chironomus. 33 



of the larva the oesophagus, proventriculus {pv)^ stomach (*), 

 and intestine are to be seen. The stomach is still filled with 

 the remains of the vitellus. In the abdomen also we see the 

 central nervous system, consisting of eleven ganglia : some of 

 the anterior and posterior ganglia lie close together ; but the 

 middle ones distinctly show their double commissures. 



This larva, constantly twisting about and working with 

 its fore feet, whilst the hinder feet serve it rather as points 

 of attachment, feeds upon the finest Algse {Spirogyra)^ 

 and at the same time surrounds itself with the detached fila- 

 ments of the Algae. These become interlaced by giving off 

 side-shoots, and thus form a canaliform cocoon which is in- 

 habited by the larva. Here it is constantly in motion, its 

 abdomen twisting about in all directions ; and this movement 

 is indispensable to the larva, as by it the cocoon is widened 

 and at the same time the deteriorated water contained in it is 

 replaced by fresh. From time to time also the larva comes 

 out and swims about very briskly in the water, still always 

 moving in a serpentine manner. This occurs frequently at 

 night. After such excursions the larva takes to the nearest 

 cocoon without caring whether this belongs to itself or to 

 another. 



The larva grows very rapidly, so that within six or seven 

 days it becomes four or five times its original length, and at 

 the same time the second form of the metamorphosis, the pupa, 

 is developed in it, the parts of which, such as the compound 

 eyes, the feet, wings, &c., already shine very distinctly through 

 the clear integuments of the larva (fig. 3) . Even the ovaries 

 do not slumber, ova are developed in them. 



At last, after the third moult, the larva measures 4 millims. 

 in length ; its head has become much smaller in proportion ; 

 the fore feet have become elongated ; the chitinous skin has 

 acquired a very pretty, delicate rose-colour, which is most per- 

 ceptible on the last abdominal segments, and is caused by the 

 development of the pupa-skin*. The movements of the larva 

 in the cocoon become perceptibly weaker, and finally cease 

 almost entirely. It then casts off the fourth skin, and thus 

 becomes transformed into the very remarkable pupa. 



The pupa (fig. 4) measures 3 millims. in length, and has a 

 longish head, which, when seen from the side, is not unlike 

 that of a cat, a thorax with three pairs of very long legs, and 

 a nine-jointed abdomen, which is covered with an immense 

 number of paired small hairs and longer single setse. The 



* Leuckart, " Die Fortpflanzimg und die Entwicklung der Pupiparen," 

 Abhandl. der Natuxf. Gesellsch. zu Halle, 1858, iv. p. 147. 



Ann. & Mag. N. Hist. Ser. 4. Vol. viii. 3 



