OF THE TRACHEA IN INSECTS. 43 



From analogy with other tufted tracheae, it is probable that the tubules are long, and 

 that they branch occasionally. The impression, however, left on my mind after examining 

 them carefully, was rather the reverse ; but, as above stated, they lie so thickly together, 

 that I cannot speak positively. 



In Tenthredo the trachese were also in tiifts, like PI. III. fig. 4, which represents those 

 of Tipula, consisting, however, only of from three to ten tubules. These latter branch 

 several times. However, the tracheae are far less numerous than in Bomhus, and have 

 altogether a very different aspect. In Ophion liiteum (PI. III. fig. 7) the contrast is still 

 more striking. The tracheae are few, inconspicuous, and have entirely lost the tufted 

 character. They give off straight branchlets at acute angles ; and the end tubules are 

 long, slender, and straight. The branches do not keep each to a single egg-tube, but 

 pass freely from one to another. In Athalia spinarum the tracheae generally resembled 

 those of Tenthredo, but they were not in such well-marked tufts. In a small species 

 belonging to the Ichneumonidse, the tracheae resembled those of Ophion, biit the branch- 

 lets were waved and twisted instead of straight. 



In Acheta the tracheae are much like those of OpUon, but on a larger scale. In Gryllus 

 I did not get a good view of the tracheae, and especially not of their terminations. They 

 were more waved than in Acheta. In Locusta (PI. III. fig. 6) they were quite different 

 from those of Acheta, or, so far as I could see them, of Gryllus. The large branches give 

 off short stout branchlets, almost as in JSombns, except that they are more waved. The 

 branchlets end abruptly, and give off tufts of tubules, like those of Tenthredo. The 

 tubules, however, are smaller in proportion to the branchlets, so as to afford a stronger 

 contrast. Moreover they are less frequently branched. In Forficula (PL III. fig. 9) 

 I did not see the fine ends. The tracheae were sunply branched ; and the branchlets 

 were long, much twisted, and of uniform diameter for considerable distances. In Carabus 

 the trachecB branch dichotomously -towards their ends. The systems are rather large. 

 Often two or three fine tubules spring from the side of the branchlets. In Lticamis cervus 

 and Amphimalla soJstitiaUs I was unable to see the fine tubules. In HydropMlus piceus, 

 Necrophorus vespUlo, and N. hnmator, the tracheae were generally in tufts, almost as in 

 Bombus, but the tubules far less numerous. In these insects the tubules certainly di^dde. 

 In Chrysopa (PL III. fig. 3) the tracheae end in tufts. The tubules in each are few in 

 number, straight, and divergent like a fan. They often give off one or two still smaller 

 tubules. Except that they are in tufts, they much resemble those of Ophion. The 

 tracheae inPanorpa, Limnephilus, and I beHeve also in lAbellula, resemble those of Chry- 

 sopa. In CampcBci margaritaria they are in tufts, as in Tenthredo ; but the tufts are 

 not above a quarter as large as in that insect. In Bip)parchia I was only once able to 

 see the tubules. They are represented in PL III. fig. 8. Pigs. 8' and 8" represent all 

 that was visible after intervals of a quarter of an hour. In Pieris brassicce also I was 

 unable to see the finer branchlets. In Tipula the tracheae were like those in PL III. 

 figs. 4 & 5. Unlike as are these two figures, the mode of branching is in reality very 

 similar, and would be seen if the tracheae of fig. 4 were extended as they are on the 

 larger egg-germs. In Eristalis tenax and a large species of Ilmca (PL III. fig. 2), 

 the tracheae were intermediate in character between those of Necrophorus and Bombus. 



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