OF THE TRACHEvE IN INSECTS. 
47 
Fatty Tiss»e. (PI. IV. figs. 8, 9 & 10.) 
In Tenthredo the fatty tissue consists principally of large round c Us. The tracheae 
are peculiarly straight and stiff-looking; they branch occasionally, and finally end in 
small tufts of froin two to six tubules. In Vespa the tracheae resemble those of Tenthredo. 
In Bombus muscorum the branches of the tracheae have the same straight, even character, 
and often run for some distance without branching. They end in tufts of straight tubules 
which are generally not very numerous and do not branch often. 
In Hydrophilus piceus also the tracheae are in tufts. 
In the larvae of Lcmpyris and Zucanus, and in Scarabaus, the fatty tissue consists of 
round masses, on which I did not ascertain the mode of distribution of the tracheae. 
In Forficida the fatty tissue is in large flakes, here and there running into one another. 
The tracheae are long and rather thin in proportion. Tiny branch seldom, and generally 
at obtuse angles. "When the flake is broad, the trachea given to it generally emits several 
branchlets. When it is narrow and ribbon-like, a small branch generally runs along it, 
and divides only at long intervals. 
In the larva of Lasiocampa ritbi and of Mamestra brassiccc, in Jphrophora spumoria, 
in Tiptda, and in Acheta domesiica, the trachea? are nearly as in Forficida, and they 
break up gradually into a few, long, straight tubules. In Fentatoma the tissue consists 
of thimble-shaped lobules, connected by their bases. A trachea enters each, and breaks 
up gradually as in PI. IV. fig. 9. In Cynips lignicola (PI. IV. fig. 10) the arrangement 
is very peculiar. The trachea? are shaped like rolling-pins, and scarcely taper at all, being, 
even at their ends, xrfeoth of an inch in breadth. Prom their ends and sides spring nu- 
merous fine tubules, about 10 o 00 th of an inch in diameter, and as much as, or even more 
than, -^oth of an inch in length. The tubules scarcely ever branch, though in one or two 
cases I saw a dichotomous division. 
Jfuscles. (PI. IV. figs. 12 to 18.) 
On the muscles of the abdomen in Bombus and Vespa thus end in tufts. 
The thoracic muscles of these two genera have a number of large, parallel, saccular, 
transverse trachea?, separated by intervals scarcely greater than their own width. They 
end suddenly in a number of very short, thick branchlets (PI. IV. fig. 14) ; and the 
saccular branches give off similar little systems from their sides. In Ophion the system * 
is similar, though the branchlets are more elongated. 
In Bombus also the tracheae of the thoracic muscles are similar ; but I could follow the 
terminal tubules rather further. The thickness of the muscle, however, prevents them from 
being seen well. 
In Fanorpa (PI. IV. fig. 12) the tracheae on the abdominal muscles are straight, and 
the tubules expand like the rays of a fan. On the muscles of the thorax the tracheae 
are sometimes waved ; but the mode of branching may be best understood by referring 
to PL IV. fig. 18. In Athalia spinarum the tracheae often end in tufts. The branchlets 
run across the muscles, and divide like a fan, but rather irregularly. Often the side 
branchlets diverge at first, and then curve round so as to become subparallel. Sometimes, 
