OF THE TRACHEA IN INSECTS. 47 



Fatty Tissue. (PI. IV. figs. 8, 9 & 10.) 



In Tenthredo the fatty tissue consists principally of large round cells. The tracheae 

 are peculiarly straight and stiff-looking ; they branch occasionally, and finally end in 

 small tufts of from two to six tubules. In Vespa the tracheae resemble those of Tenthredo. 

 In Bonibiis muscorum the branches of the tracheae have the same straight, even cliaracter, 

 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 Hydrophihis picetis also the tracheae are in tufts. 



In the larvge of Lmnpyris and Lucanus, and in Scarcibaius, the fatty tissue consists of 

 round masses, on which I did not ascertain the mode of distribution of the tracheae. 



In Forficula the fatty tissue is in large flakes, here and there running into one another. 

 The tracheae are long and rather thin in proportion. They branch seldom, and generally 

 at obtuse angles. Wlien 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 ruM and of Mamestra I)7'assicce, in Aphrophora spumaria, 

 in Tijmla, and in Acheta domestica, the tracheae are nearly as in Forficula, and they 

 break up gradually into a few, long, straight tubules. In Pentatoma 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 Ugnicola (PI. IV. fig. 10) the arrangement 

 is very peculiar. The tracheae are shaped lilce rolling-pins, and scarcely taper at all, being, 

 even at then' ends, too o^h of an inch in breadth. From their ends and sides spring nu- 

 merous fine tubules, about roooo^h of an inch in diameter, and as much as, or even more 

 than, a^th of an inch in length. The tubules scarcely ever branch, though in one or two 

 cases I saw a dichotomous division. 



Ifuscles. (PI. IV. figs. 12 to 18.) 



On the muscles of the abdomen in JBombus and Vespa thus end in tufts. 



The thoracic muscles of these two genera have a number of large, parallel, saccular, 

 transverse tracheae, 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 Bomhtis 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 Panorpa (PL 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 PI. IV. fig. 18. In Atlialia spiuarum 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, 



