ARTHUR DEWITT WHEDOX 389 



INTERNAL ANATOMY 



The comparative anatomy of the Odonatc abdomen has re- 

 ceived very scant attention. This is especially true of the adult 

 and even in extensive monographs, as that of Amans (1885) on 

 flight, the abdomen is scarcely mentioned. Investigation into 

 anatomy has l^een prompted by its necessity in the solution of 

 physiological problems and was carried only far enough to meet 

 such need. Great interest in flight has led to a thorough stud}- of 

 thoracic structure ; the tracheae have been extensively mapped by 

 workers on respiration for half a centur}^ past, and very carefully 

 studied bj' Tillyard (1917) in his recent work on rectal respiration; 

 the abdominal muscles have been discovered and connected with 

 respiratory functions by investigators from Dufour (1852) to 

 Wallongren (1914). Plateau, again interested in respiration, 

 worked upon the abdominal nmsclcs of the imago, but with this 

 exception European writers have virtually limited themselves to 

 the larva of Aeshno grandis as material. In this country Marshall 

 (1914) has summed up our knowledge of the general mor])hology 

 and histology of the alimentary canal and reproductive organs of 

 the Li'bellulinae in his paper on Lihellula quadrimaculata, while 

 for the most specific accounts of the s^^stems of the Zygoptera 

 we are indebted to Calvert's careful studies of the larvae of Coro, 

 Mecistog aster, and Thaumatoneura (1911, 1911, and 1915). 



The present paper is concerned with the digestive, nervous, re- 

 productive and muscular systems of both the larvae and the 

 adults of species selected from each of the three larger groups of 

 Odonata. The object of the account is four-fold: (1) to sum- 

 marize our knowledge of past work, (2) to add new facts that have 

 appeared as the dissection of worked types was repeated or that 

 of new types carried out, (3) to compare types of the suborders, 

 and (4) to compare the structures of the adults with those of the 

 larvae. This should result in a clearer view than has as yet been 

 presented in the comparative morphology of the Odonata, and 

 throw some additional light upon the functions and adaptations 

 of the abdomen. 



The work upon the reproductive system included here will ])e 

 found less complete and definite than that on the other systems 

 because of the lack of full development and of functional condition 

 in all but mature imagoes. 



TRANS. AM. EXT. SOC, XLIV. 



