Vol. XXvi] ENTOMOLOGICAL NEWS. 435 



Studies on Costa Rican Odonata. 



VII. The Waterfall-Dwellers: The Internal Organs of Thaum- 

 atoneura larva and the Respiration and Rectal Tracheation of Zy- 

 gopterous Larvae in general. 



(Continued from page 395) 



By PHILIP P. CALVERT, Pn.D., University of Pennsylvania, 



Philadelphia. 



Our knowledge of the whole subject of the respiration of 

 Zygopterous larvae is still very indefinite, and it seems worth 

 while to summarize it such as it is. 



CLASSIFICATION OF THE TRACHEAL GILLS OF ODONATE LARVAE. 



Dufour (1852), grouping all the Odonate larvae known to 

 him under the four genera, Aeshna, Libellula, Calopterix and 

 Agrion, gave as generic characters for the first three "Branch- 

 ies interieures ou rectales," and for the last "Branchies ex- 

 terieures ou caudalcs . . . et servant aussi de nage- 

 oires." He added "Comme on voit, la nature et la position des 

 branchies etablissent entre le Calopterix et I' Agrion une dis- 

 tance anatomique enorme" (p. 72). Hagen (1853), recogniz- 

 ing five families, gave for Libelluliden, Gomphiden and Aesch- 

 niden "Darmkiemen," for Calopterygiden "Darm und Schwanz- 

 kiemen," for Agrioniden "Schwanzkiemen" (pp. 261-9, 3 11 )- 

 Rousseau (1909, pp. 2, 43, 45) has accepted the same distinc- 

 tions so far as "branchies" are concerned. 



Roster (1885, p. 259), on the other hand, grouped Agrion, 

 Lcstes and Caloptcryx as Caudobranchiati, Aiia.r, Libellula and 

 Aeschna as Rectobranchiati, although Dufour (1852, p. 83) 

 had employed the same words, in the form of French adjec- 

 tives, in the different sense implied by his classification quoted 

 above. Roster's terms were synonymous, as group names, 

 with the earlier Zygoptera and Anisoptera and were so recog- 

 nized by systematic writers.* 



FUNCTIONS OF THE THREE CAUDAL APPENDAGES OF ZYGOP- 



Tia<ous LARVAE. 



Reaumur (1742, p. 405), who regarded these appendages as 

 "nageoires" (fins), and Roesel von Rosenhof (1749, pp. 41 et 



*. g., de Selys-Longchamps, Ann. S<>c. Knt. I'.di;. xxxi, pp. 75, 

 80, in a "Liste des Odonates d'Europe en 1887." 



