386 PROCEEDINGS OF THE NATIONAL MU8EJM. vol. .37. 



In pacifica, annulata, and magnifica the dorsal spots on 4-6 occupy 

 all or nearly all the area between the base of each segment and the 

 transverse carina. The only s])ecies with which annulata and iKicifica 

 might be confused in length of antehumeral thoracic stripe is georgina, 

 which has the abdomen with relatively much more black, the yellow 

 on 4-6 widely separated from the base of each segment. Both mag- 

 nifica and georgina have the antehumeral thoracic stripes shorter than 

 in annulata and pacifica. Magmfica is, moreover, distinct by a number 

 of characters (see description of magmfica), leaving annulata as the 

 only species which might be confused with pacifica. In annulata and 

 magnifica the dorsal stripes on 4-6 are not interrupted with black in 

 the middorsal line, and the latero-ventral metathoracic carina is 

 broadly yellow. For other characters, see descriptions of annulata 

 and magnifica. There is no doubt that fiavipennis Walsh is a syno- 

 nym of pacfica and not of annulata as Hagen supposed. In Walsh's 

 descri])tions of illinoiensis and fiavipennis , each descrii)tion based on 

 a single female, his descriptions of the vulvar lamina refer to another 

 structure. 



M. pacifica is readily recognized at some distance on the wing at 

 Bluffton, where it is associated with tseniolata and wahashensis (during 

 recent years I have not taken illinoiensis here). In flight one gets 

 the impression of an insect largely yellow in color. The yellow is 

 conspicuous on the other 2 species, but to no such extent as on pacifica. 

 M. illinoiensis gives one the impression of a black inject largely 

 yellow at the apex of the abdomen. The same is undoubtedly true 

 of allegJianiensis. 



The Wabash River at Bluffton during recent years has been over- 

 run at the ri])ples by willow herb, so the river in summer is reduced 

 to a succession of pools of greater or less length. On the banks 

 Hibiscus militaris has become thoroughly established at the water's 

 edge. These pools seem to l)e an itleal home for the Macromias. 

 (See pis. 35 and 36.) 



The flight of pacfica is generally less swift than that of txniolata 

 and wahashensis and it ranges less widely, patrolling possibly only 

 one ])ool, while the others return to the same point only after longer 

 intervals. Individuals of all 3 species follow the same track over 

 and over, crossing the river at a certain point, returning over a certain 

 patch of willow herb, turning out from the shore line at a certain 

 clump of hibiscus, and going and coming over the same or nearly the 

 same course and not following the pools in a circular manner. More- 

 over, individuals of successive generations have followed the same 

 course as their predecessors, as I have observed at the pools where I 

 have found individuals most numerous and where I have collected 

 for several years. The configuration of vegetation and water is a 

 positive factor in determining the course of flight. Much of my sue- 



