NATURAL HISTORY WORK IN CART AGO 59 



adaptability to temperature, since it is exposed to freezing 

 weather in tlie United States while in Costa Rica it has never 

 to contend with that condition. 



The wide distribution of Anomalagrion hastatum has ap- 

 parently not led to the formation of different races charac- 

 teristic of different parts of its area of occurrence, as in many 

 other species of animals. Thus, the Costa Rican males have 

 an average length of abdomen of 18.3 millimeters and of 

 hind wing of 10.5 millimeters; corresponding figures for in- 

 dividuals chiefly from New Jersey and Pennsylvania are 

 18.9 and 10.8. The females are slightly larger, longer in 

 abdomen and have distinctly longer wings. Figures cor- 

 responding to the above for the so-called "black" females 

 are: Costa Rica 19. i, 13.2; United States 19.5, 12.9; and for 

 the "orange" females: Costa Rica 19.2, 13.1; United States 

 19.2, 13. The slight differences here shown may in part at 

 least be due to unequal shrinkage of the abdomens after 

 death, as all these measurements are from dried specimens. 



The abdomen of the male is yellow, becoming more and 

 more of an orange from its fore to its hind end, with marked 

 black spots on all but the last two or three segments. The 

 size and shape of these black markings vary much, but the 

 tendencies of their variation are the same in specimens from 

 Costa Rica and from the United States. 



The females for the most part appear in two forms; one, 

 known as the "orange" female, has a large (anterior) part 

 of the abdomen orange, the other, the "black" female, has 

 the entire upper surface of the abdomen black. Other less 

 conspicuous color differences also exist. The majority of 

 dragonflies as they grow old show on one or more parts of 

 the body an appearance similar to the "bloom" of a plum or 

 dark grape, whence they are said to be "pruinose." This 

 pruinosity is frequently to be found on the black females of 

 Anomalagrion but not on the orange females. Transitional 



