FIELD BOOK OF INSECTS. 



on citrus leaves, and some authors use thoas as its specific 

 name, but this should be applied to a more southern 

 species. The horns on the larva are fleshly affairs, which 

 may be withdrawn or extruded through a slit in the 

 thorax; not only is their sudden appearing supposed to 

 frighten the larva's enemies but these horns exhale an 

 odor which, in some species, is quite disagreeable in 

 other words, the young of the beautiful creatures are 

 insect skunks. The meaning of the color on the right 

 side of the adult, as shown in Plate I, is explained on p. 

 115. The wings are more largely yellow below than above. 

 The home of this species is the North American subtropics, 

 but it seems to be working northward (where the larva 

 feeds on prickly ash and Ptelea) and has been taken in 

 Canada. There are from two to four annual broods, 

 depending upon location. 



Papilio One of the rules about scientific names is 



glaucus and that the first name used for a species, if 

 accompanied by a description, shall be 

 the name. Now Linnasus evidently intended to call the 

 yellow Tiger Swallow-tail turnus, but, in his description, 

 he first referred to the dark form of the female (Plate 

 XXXVI), which is rare in the North but common in the 

 South, as glaucus; therefore glaucus is the name of the 

 species, but you may call it turnus. The larva feeds on 

 orchard and other trees, especially wild cherry, but is 

 never injurious. It has the luxurious habit of spinning 

 a web on top of a leaf, drawing it so tightly that it has a 

 spring couch upon which to rest when not feeding. There 

 is a pair of eye-like spots on the thorax, and, when the 

 true head is drawn under so that these appear to be on the 

 head, the thoracic "horns" are shot out, and the front 

 part of the body is swayed back and forth, even you might 

 hesitate to disturb its siesta. 



The Spice-bush Swallow-tail is sometimes 



called the Green - clouded Swallow-tail be- 

 cause of the color of the upper surface of the 

 hind wings; the female does not have the green so pro- 

 nounced but has hazy blue spots along the cloud's outer 



140 



