gastric 

 nerv'es 



48 TJie Larva of Chironoiniis 



only vestiges of a tracheal system, is an argument against 

 their respiratory character — not a conclusive argument, 

 however, for at a later time spiracles form close to the 

 junctions of the segments. 



stomato- A special system of stomaio-gastric nerves and ganglia 

 is found upon the oesophagus and the fore part of the 

 aorta (fig. 38) ^ Paired nerves proceed forwards from the 

 lobes of the brain, and unite to form a frontal ganglion 

 on the oesophagus. From the frontal ganglion a median 

 recurrent nerve passes backwards between the aorta and 

 the oesophagus. Beneath the brain this divides into 

 two branches, which enter paired ganglia, and con- 

 tinue beyond them to the stomach. In some other 

 Dipterous larvae^, paired nerves are found, which pass 

 backwards from the brain, and enter small ganglia 

 on either side of the aorta. In the Chironomus-larva 

 similar ganglia are seen (fig. 38, di\g) ; we are not, how- 

 ever, quite satisfied in this case as to the nervous connexion 

 Avith the brain. In some other insects a more extensive 

 system of paired ganglia exists, sending branches to the 

 oesophagus, aorta, and occasionally to the salivary' 

 glands. 



Sense- The orgaus of special sense found in the larva are the 



eye-spots, the antennae, and the sensory prominences on 

 the last segment. The eye-spots are little more than 

 blotches of pigment without lenses. There are two 

 pairs of them. In the larvae of several Culicidae the 

 anterior pair become complex. In Corethra. Weismann 

 found that the fresh-hatched larva possesses only one 

 pair ; that the second pair are developed in front ot 

 the first as a series of folds in two deep invaginations 

 of the epidermis ; that the first pair then begin to 

 degenerate ; and that the second j)air are true compound 



^ This is the sijmpathetic system of Johannes Miiller, 1828. 

 '^ Phalacrocera (Miall and Shelf ord, 1897, \>\. x, figs. 19. 20). 



irgans. 



