3o6 A YEAR OF COSTA RICAN NATURAL HISTORY 



ing I fell in with a flock of about twenty-five individuals 

 flying lower than usual and by standing still in the hot sun 

 and waiting until one was very close to me I succeeded in 

 capturing enough specimens to show that the flock was com- 

 prised of four species — the very widespread Pantala flavescens 

 and P. hymeyicEa and the less widely found Tramea cophysa 

 and Macrothemis hemichlora. These differently-colored and 

 -marked species flew around and among each other, some- 

 times seeming to drift in one direction, sometimes in another, 

 chiefly employed in catching small insects in the air. They 

 rarely alighted and apparently sustained themselves with 

 little muscular effort except when the wind blew. In Chap- 

 ter V we have already given brief descriptions of the species 

 of Pantala. The genus Tramea is closely allied and likewise 

 has the hind wings very broad at the base. Those interested 

 in identifying them may recognize Pa?itala by the third and 

 fourth segments of the abdomen (counting always from its 

 anterior end) having each three cross-ridges which almost 

 entirely surround the body, while the same segments in 

 Tramea have only two cross-ridges each. Moreover, in 

 Pantala in the apical third of the wings, are two parallel 

 and closely adjacent veins (M2 and Rs) which are strongly 

 waved with two convexities directed forward; these same 

 two veins in Tramea are almost straight and only as they 

 approach the hind margin of the wing are they curved toward 

 it. Tramea cophysa has a brown band, about an eighth of 

 an inch wide, on the base of each hind wing reaching from 

 the fifth vein (counting that on the front margin as the 

 first vein) to the hind margin; this insect is of very nearly 

 the same size as the two Pantalas. The peculiarity of 

 Macrothe^nis is that the tooth, which is present on the under 

 side of each of the two claws with which each leg of a dragon- 

 fly is tipped, is here so large as to equal or exceed in length 

 and thickness the point of the claw itself. The claw conse- 



