Introduction to Auimal Morphology. 391 



are many tracheae on its papillary ridges, which in the 

 aquatic larvae of many dragon-flies are extended into trachei- 

 ferous lamellae, named tracheal gilh,^ which by the opening 

 and shutting of the anus are kept bathed with currents of 

 water, and thus serve as respiratory organs. Some Hymen- 

 opterous and Pupiparous Dipterian larvae -have no anus, and in 

 ant-lion larva the rectum, thus cut off from the stomach, 

 becomes a spinning apparatus, with a fine outlet, and 

 receives the Malpighian tubes. In the larvae of Dyticus 

 and Hemerobius, as well as in Myrmeleo, there is no mouth, 

 but there is a large opening at the point of each of the 

 powerful maxillae leading by a canal into the oesophagus. 



Salivary glands are usually present (absent or 

 small in Ephemeridge, Odonata, Scalidse, Aphides, &c.) 

 They are two long, lobed pouches in Termes ; tortu- 

 ous tubes in Beetles, Diptera, and Lepidoptera, or 

 1-3 pair of acinose glands in Hemiptera and Or- 

 thoptera. Panorpa has six large glands in the male, 

 and only one minute pair in the female. The duct is 

 dilated in Mantis, Lucilia, &c. Fine longitudinal or 

 tortuous brown or whitish Malpighian tubes open into 

 the intestine (except in Podurae, Coccidse, Aphis, and 

 Chermes), but present in Lepisma and in most other 

 insects. There are four in most Diptera and Hemip- 

 tera, six in Lepidoptera and Neuroptera, four or six 

 in Beetles. They open close behind the stomach in 

 Hymenoptera, Diptera, Cicadse, Lepidoptera, &:c. 

 Larvae have usually the same number of tubes as 

 adults, except in Bees, whose larvae have only four. 

 They rarely branch, but sling-like unions between 

 their ends are found in some, and sometimes vesicular 



* Similar to these are the many-jointed cerci anales of many Beetles 

 and Lepidoptera, which are possibly the representatives of the tail oars of 

 Copepods. 



