ARTHUR DEWITT WIIEDOX 375 



in the plant tissue in or near the contained water, in accordance 

 with the gen^^ral habit of the Zygoptera, it would often be nec- 

 essarj'^ for the female to reach far down into the crevices possibly 

 too narrow to admit of the entrance of her thorax and wings. 

 The long abdomen with the ovipositor near its end would there- 

 fore be a distinct advantage, and it will be of great interest to 

 ascertain, by future observations, if the lengths of the abdomens 

 seen in various members of the legion Pseudostigma of de Selys 

 are correlated with peculiarities in the length of the plants or 

 othei- objects in which they oviposit." 



It will be noted that this explanation would not include the- 

 male, l)ut in his later account (1917) he adds: "The abdomens of 

 the males of the species of Mccistoga-ster are as long or longer 

 than those of the females. Their length of course cannot be ex- 

 plained in the way. suggested for the females, but is possibly due 

 to the necessary correlation in length which nmst exist between 

 the two sexes to enable them to assume the characteristic mating 

 position." 



Largely gaining his information from C'alvert's work on Mecis- 

 togasfcr, Tillyard states in his "Biology of Dragonflies" (1917), 

 "In the Pseudostigmatinae, the abdomen has become excessively 

 slender, and of enormous length. This is a secondary develop- 

 ment, correlated with the habit of laying the eggs in the water 

 collected between the bases of the leaves of epiphytic Bromeliads." 



A careful examination of the literature of the Odonata fails 

 to reveal further references to the subject. Studies upon ovipo- 

 sition, flight, respiration and other phases of the life of these 

 insects seem entirely silent so far as any direct suggestions are 

 concerned. 



DEFINITION OF THE PROBLEM 



A consideration of these views together with a general survey 

 of the Odonata sets before us two problems: (1) the one 

 concerned with the origin of the elongated abdomen as a group 

 character, (2) the other having to do solely with the further modi- 

 fication or adaptation of the type form to meet environmental 

 conditions. The first is a question of phylogeny, and as the 

 determining factors involved are, and may forever be, hidden in 

 the obscurity of Paleozoic time, it is now far l)cyond the possibility 



TRANS. AM. ENT. SOC, XLIV. 



