BLOOD-GILLS 475 



and breathe solely by leaf-like tracheal gills (Fig. 456, br~) attached to 

 the under side of the second to sixth abdominal segments. Those of 

 the European Liponeura are said by Wierzejski to be branched, tree- 

 like. Also immediately in front of the anus and behind the last 

 sucker are four membranous sacs provided with tracheae, but which 

 are not capable of being withdrawn. These are said by Miiller to be 

 the same as what Dewitz states to serve as gills, and by Wierzejski 

 they are homologized Avith the four anal gills of Chironomus. 



* 



The double mode of respiration in the larva of the horse bot-fly has been 

 described by Scheiber. On the hinder end of the body are the stigmatic plates, 

 which contain two lateral gill-plates and the middle stigmatal leaf. Besides this 

 there is a pair of slightly developed prothoracic spiracles. The embryo and also 

 freshly hatched larva of Gastrophilus equi do not possess these gill-plates, but on 

 the end of the body are, according to Joli, two long thread-like gills. The 

 freshly hatched larva of the allied Cephenomyia rujibarbis bears two caudal 

 projections. (Kolbe.) As in shrimps and other Crustacea the gills are kept in 

 constant motion, the water being driven over them by the rapid movements of 

 the telson, so in the larval may flies, and in the case-worm (Macronema), the 

 gills move more or less rapidly. In case-worms as well as larval Perlidse, 

 Sialidse, Paraponyx, and Hydrophilidse the abdominal region is constantly moved 

 to promote respiration. (Kolbe.) 



Blood-rjUls. Fritz Miiller describes in trichopterous larvae certain 

 delicate anal tubular processes into which the blood flows, and \vhich 

 do not as a rule contain tracheae, though occasionally very fine 

 tracheal branches. Miiller compares them with the gills of crabs 

 and of shrimps. They are eversible finger-like tubules. They are 

 used Avhen the tracheal gills are temporarily not available. Their 

 number varies even in the same genus. There are six in certain 

 Khyacophilidae ; five in different Hydropsychidae ; in Macronema 

 there are four, and they are green Avhen filled Avith the green blood 

 of that insect, the tracheal gills being Avhitish. In the freshly 

 hatched larva, while the tracheal gills are present, no anal blood-gills 

 are visible. Similar blood-gills also occur in the pupae of certain 

 caddis-flies. (Pictet.) 



Similar anal gills filled with blood occur in the larvae of the fire- 

 flies (Lampyris, etc.), and perhaps, Kolbe thinks, serve for respira- 

 tion, though other authors believe them to be adhesive organs. 



The larva of Pelobius has true blood-gills. (Schiodte. See p. 461.) 



The eversible ventral segmental sacs of Scolopendrella, Campodea, and 

 Machilis, as well as the ventral tube (collophore) of Podura, Smynthurus, etc., 

 may, as Oudemans and Haase have suggested, serve a respiratory purpose, 

 though they lack tracheae, and differ from blood-gills in containing no gases ; 

 yet the blood is forced into them, causing their eversion. Oudemans observed 



