OF THE TRACHEA IN INSECTS 
35 
Salivary Glands. 
In the larva of Euplexia lucipara and of one of the Mamestra? the salivary glands have 
few branchlets, which are simple and without numerous tubules. The duct was gene- 
rally free from tracheae. 
In Chrysopa the mode of branching is similar, but the tubules are not quite so long. 
In Bombus lucorum the tracheae on the thoracic glands were in tufts. In Tentatoma 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 curved, 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 Musca the branching is simple, and not in tufts. It is much like the 
figure in PI. IV. fig. 8 
Ccvca. (PI. I. figs. 10 & 11.) 
The caeca of Acheta are two thick pulpy organs, one on each side of the stomach. 
They have some large vascular tracheae, 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 trachea? 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 or<*an from its 
base and give off transverse branches, one of which is represented in PI. I. fig. 12. Each 
boss has also a branch or more, which give off from their outer side long straight tubules 
(PI. 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 ^th 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 Musca, the 
mode of branching is simple, and offers no great peculiarity. 
Sucking Stomach. (PI. I. fig. 9.) 
* 
In Bombus terrestris, Vespa vulgaris, Ophion, Tenthredo Inteus, Ichneumon, Ca<mpa>a 
morgaritaria, Bieris brassicce, Tipula, 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 way alon«* 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 O 
