OF THE TRACHEA IN INSECTS. 35 



Salloarii Glands. 



In the larva of Huplexia liicipara and of one of the Ilamestrce the sali^'^ary glands have 

 few branchlets, vs^hich are simple and without numerous tiibules. The duct was gene- 

 rally free from tracheae. 



In Clirysopa the mode of branching is similar, but the tubules are not quite so long. 

 In Bombus liicorum the tracheae on the thoracic glands were in tufts. In Fentatoma the 

 tracheae are very nearly like those of the stomach, but with perhaps rather fewer tubules. 

 Eristalis has four salivary glands ; two are cylindrical with circular bosses, the other two 

 resemble in shape the ordinary long salivary glands of caterpillars. On all four the tracheae 

 are in tufts as on the oesophagus, and the tubules are greatly curA^ed, but in each tuft 

 there are very few, and even sometimes the branching scarcely seems to be in tufts at all. 



In the larva of lliisca the branching is simple, and ]iot in tufts. It is much like the 

 figure in PL IV. fig. 8. 



Cceca. (PI. I. figs. 10 & 11.) 



The cseca of Acheta are two thick pulpy organs, one on each side of the stomach. 

 They have some large vascular tracheas, which divide several times and then run into 

 the corresponding branches on the other side of the organ, as in PL I. fig. 10. The 

 branchlets have a very rigid appearance, as they are broad at their origin, and taper 

 very quickly. In the larva the tracheae are nearly similar, but more elongated. 



The character of the tracheae is nearly the same in Gryllus as in Acheta, but the in- 

 osculations are less conspicuous, and the branchlets are rather more elongated. 



In Chrysopa the caecum is cylindrical, but tapering to the free end. It is divided by 

 twelve constrictions into well-marked bosses. Large tracheae run up the organ from its 

 base and give off transverse branches, one of which is represented in PL I. fig. 12. Each 

 boss has also a branch or naore, which give off from their outer side long straight tubules 

 (PL I. fig. 11). I counted 328 of these long tubules in one half of one boss, so that 

 the total number must be very large ; and as each one is about ro^^li of an inch in length, 

 the total length of the whole must be considerable. 



In the long tubes attached to the front end of the stomach in the larva of Ilusca, the 

 mode of brandling is simple, and offers no great peculiarity. 



Sucking Stomach. (PL I. fig. 9.) 



In Bombus terrestris, Vespa vulgaris, Ophion, Tenthredo luteus. Ichneumon, Campcea 

 margaritaria, Pleris brassicce, Tipiila, and Noctua gamma, this organ has no tracheae. 



In Musca, on the contrary, it is well supplied with tracheae in pretty little systems. The 

 tracheae branch simply, and the tubules have a tendency to run a little Avay along the 

 parent stem, and then curve out from it in a beautiful manner. In the larva of Musca 

 it appeared to be free from tracheae. 



In Eristalis it is poorly supplied, but the tracheae are of the same type as those on the 

 stomach. The duct also is supplied in a similar manner. 



F 2 



