2)6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 23 



6. The respiratory chamber of the intestine is probably the colon 

 rather than the rectum, the latter forming only the terminal region 

 of the intestine connecting the respiratory chamber with the anus. 



7. The "cercoids" are here regarded as true cerci, and the anal 

 lobes as epiproct and paraprocts. The caudal gills of zygopterous 

 larvae are lobes of the epiproct and paraprocts. The primitive respira- 

 tory organs of odonate larvae were probably paired lateral gills of 

 the abdomen, which are still retained in some modern species. 



8. Only the thorax of the larva resembles the corresponding part 

 of the adult; the larval head and abdomen are constructed entirely 

 for purposes of the aquatic larva, the thorax serves equally well for 

 both larva and adult. 



9. The similarity of the thoracic structure in both larva and adult 

 suggests that the primitive young dragonfly, before it took to the 

 water, resembled the adult as much as any modern terrestrial nymph 

 resembles its parents, but probably at that time the adults had not yet 

 attained the status of perfect dragonflies. 



10. The metamorphic changes of the aeschnid larva in its trans- 

 formation to the imago are equivalent in degree to those of many holo- 

 metabolous insects. The head, the labium, and the abdomen are en- 

 tirely made over, the alimentaiy canal and the tracheal system are 

 simplified, the labial muscles are histolysed and re-formed, the great 

 mass of larval muscles in the abdomen are destroyed and not replaced 

 in the adult, the thoracic wing muscles simply complete their develop- 

 ment, the reproductive organs mature. 



11. The transformation that produces the imago within the cuticle 

 of the last larval instar is entirely comparable in degree to that which 

 takes place in the pupa of a so-called holometabolous insect ; though 

 it is completed without a subsequent moult, the transforming stage is 

 equivalent to a pupa, and is a preliminary stage of the adult. 



12. The dragonfly larva should be an interesting subject for experi- 

 mental studies on the role played by hormones in metamorphosis. 



REFERENCES 

 Amans, p. 



1881. Recherches anatomiques et physiologiques sur la larve de VAcschna 

 grandis. Rev. Sci. Nat., Montpellier, ser. 3, vol. i, pp. 63-74, i pi. 



ASAHINA, S. 



1949. On some archaic structures retained in Epiophlebia superstcs 

 (Odonata, Anisozygoptera). Mushi, vol. 19, pp. 49-51, 2 figs. 

 Butler, Hortense. 



1904. The labium of the Odonata. Trans. Amer. Ent. Soc, vol. 30, pp. iii- 

 133, 6 pis. 



