BUTTERFLIES OF THE DISTEICT OF COLUMBIA 61 



glabra) growing in bogs is an indication of the probable occurrence 

 of the turtlehead butterfly {Euyhydryas phaeton), while the pres- 

 ence of pigweed {Ghenopodium album), in farmyards, waste land, 

 vacant lots, gardens, and along roads, is a certain sign of the presence 

 of the sooty skipper {Pholisora catullus). 



In low open woods with large rough-barked trees, particularly 

 oaks, the presence of small cruciferous plants, especially the mouse- 

 ear cress {Sisyrnbriuvi thalianuTii) and the toothworts {Dentaria 

 laciniata and D. heterophyllu) , is an almost certain sign of the pres- 

 ence early in spring of the orange tip {Anthocharis germtia) . 



In any region the occurrence of many different kinds of butterflies 

 is more easily determined by searching for the caterpillars than by 

 hunting for the adults. In the District this is particularly true of 

 the sooty skipper (Pholisora catullus), which is small, inconspicuous, 

 wary, and elusive, while its caterpillars everywhere abound on pig- 

 weed and are easily raised to adults. It is equally true of the turtle- 

 head butterfly {Euphydryas phaeton), which is sluggish and incon- 

 spicuous and extremely local. Its caterpillars, however, form very 

 conspicuous webs on the summit of the food plant. The alder but- 

 terfly {Feniseca tarquinius) is most readily obtained by raising its 

 caterpillars, which are to be found in the masses of white woolly 

 aphids on the alders or in the leaf curls of the aphids of the beech. 

 The viceroy {Basilarchia archippus) is most easily secured by raising 

 it from its caterpillars, which are to be found on small willows and 

 on small poplars. Up to about the middle of August the milkweed 

 butterfly {Danaus j^lexippus) is readily obtained by raising the con- 

 spicuous and easily discoverable caterpillars. Wherever the giant 

 swallowtail {Papilio cresphontes) occurs its caterpillars, known as 

 "orange dogs," are easily found on various plants related to the 

 orange (family Rutaceae). In this region they are to be looked for 

 on the hoptree (Ptelea trifoliata) and on the prickly-ash {Zanthoxy- 

 lum atnericanum) , though they may occur on other trees, especially 

 on poplars. 



Specimens of butterflies that have been raised from caterpillars 

 should always be so labeled, as they are often smaller or larger than 

 individuals caught in the wild, and sometimes differ more or less 

 markedly in color or in wing form from them. 



In spite of all that has been said above, it should be constantly 

 remembered that there is no real substitute for work. Though the 

 gathering of the larger, more conspicuous, and more characteristic of 

 the butterflies in any region is always a relatively simple matter, the 

 assembling of a really representative collection necessitates long- 

 continued, monotonous, and often discouraging labor extending over 

 a long period of years. 



