OF THE TRACHEA IN INSECTS. 49 



imago, in those larvas which undergo a perfect metamorphosis (as, for instance, in those of 

 Coleoptera, Lepidoptera, and Hymenoptera) the tracheae are very unlike those of the 

 perfect insect. 



Sixthly, in these latter larvse the same type of tracheal distribution appears to be more 

 widely distributed in the different organs. Thus, while in the imago of Bomhns the 

 trachese on the stomach, ilium, and Malpighian vessels are all three very different from one 

 another, the trachese on the corresponding organs of the larva of B. mtiscoriim are very 

 similar to one another, and as in PL II. fig. 11. Again, in the larva of Luccmns the 

 oesophagus, stomach, ilium, and colon, and in that of Lampyris the stomach, ilium, colon, 

 and Malpighian vessels, had trachese respectively like one another. 



Seventhly, that in some cases the trachese of the larvae seem to agree in species where 

 those of the perfect insect are different; so that, comparing this with the preceding 

 rule, it would seem that the larval trachese are in both respects less differentiated, and 

 more in accordance with the original type than those of perfect insects. 



DESCRIPTION OE THE PLATES. 

 Plate I. 



Fig. 1. Trachese from ganglion of Acheta, x 125. 



Fig. 2. Tracheae from commissure of Carabus, x 125. 



Fig. .3. Trachese from ganglion of Bombus, x 125. 



Fig. 4. Trachete from commissure of Acheta, x 125. 



Fig. 5. Trachese from ganglion of Pentaioma, x 125. 



Fig. 6. TracheEe from ganglion of Carabus, x 125. 



Fig. 7- Trachese from commissure of Lasiocampa, x 125 



Fig. 8. Trachese from oesophagus of Eristalis, x 125. 



Fig. 9. Tracheae from sucking-stomach of Musca, x 125 



Fig. 10. Trachese from rsecum of Achet a, x 30. 

 Fig. 11. Tracheae from caicum of C7i?'2/5o/)ff, x 125. 

 Fig. 12. Trachese from c?ec\im.of Chrysopa, x 125. 

 Fig. 13. Trachese from crop of Carabus, x 30. 

 Fig. 14. Trache8efromcEsophagusofMMsc«, x 125. 

 Fig. 15. Tracheffi from heart of Bombus, x 125. 

 Fig. 16. Trachea; from heart of Musca, x 125. 

 Fig. 17. TrachefE from heart of Aphrophora, 

 X 125. 



Plate II. 



Fig. 1. Trachese from the stomach of Musca, x 125. 



Fig. 2. A few of the larger trachese from tlie stomach of Pentaioma, omitting the finer branches, x 30. 



Fig. 3. Tracheae from the stomach of Ophior„, x 125. 



Fig. 4. Trachese from the stomach of Achet a, x 60. 



Fig. 5. Trachese from the stomach of Bombus, x 125. 



Fig. 6. Trachese from the stomach of Bombus, x 125. 



Fig. 7- One of the lateral branches from the above figure of Pentatoma, showing the fine branchlets, x 125. 



Fig. 8. Trachese from the stomach of Mamestra, x 30. 



Fig. 9. Trachese from the stomach of Acheta, x 30. 



Fig. 10. Tracheae from the stomach of Vespa, x 125. 



Fig. 11. Trachese from the ilium of the larva of Bombus, x 125. 



Fig. 12. Trachese from the ilium of Tipula, x 125. 



Fig. 13. Small part of the inner membrane of a trachea, showing the spirally thickened rib, aaa, x 125. 



Fig. 14. Trachese of salivary gland of Pentatoma, x 125. 



Fig. 15. Trachese of Malpighian vessel of Atithophora, x 125. 



Fig. 16, Trachese of recurrent intestine of Aphrophora, x 30. 



VOL. XXIII. H 



