POPLAR CATERPILLARS. 449 



mountain roads. It is less common on the Maine coast. It is double- 

 brooded, appearing, says Harris, late in June, and again late in August. 

 It feeds on the balsam poplar, as well as thorn and birch. 



Mrs. Anna K. Dimmock gives a summary of its history (Psyche, 

 iv, p. 282) as follows : 



Limenitis arthemis Drury (lUust. Nat. Hist. — 1773, v. 2, pi. 10, fig. 3-4). Lintner 

 (Proc. Entom. Soc. Phil., May 1864, v. 3, p. 62-63) describes the larva and pupa of 

 this species, giving as the food-plant Populus balsamifera. Scndder (Amer. Nat., 

 Aug. 1839, V. 3, p. 330) gives Cratagus as the food- plant, and again (Psyche, Aug. 

 1874, V, 1, p. 13) adds Betula lenta and Populus to the food-plants. (See also Scud- 

 der's Butterflies of the Eastern United States.) 



16. Limenitis disippus Godart. {Basilarchia a7-chippu8 Scndder.) 



The singular caterpillars of this common butterfly frequently occur 

 at Brunswick, Me., becoming full-fed during the last week in July 

 and the first of August. They afford an admirable instance of protect- 

 ive mimicry, as they resemble a mass of bird's droppings attached to a 

 leaf, owing to their shape, attitude, and especially the dark and pe- 

 culiar pearly limy white patches on the back. The butterflies lay their 

 eggs in midsummer or later and I have found the young larvae at Provi- 

 dence September 20, in its hibernaculum, consisting of a poplar leaf 

 slit and folded, and sewed together to form a tube in which the cater- 

 pillar resides. It left its hibernaculum at Providence as early as May 

 10, 1890. It remains in the chrysalis state about ten days, my larvae 

 in Maine pupating July 31 to August 1 and the imagos emerging Au- 

 gust 10 to 11. 



Full-fed larva. — Head resinous brown, rough, coarsely granulated and vrith sharp 

 tubercles, ending vertically in two acutely knobby tubercles. Mesothoracic segment 

 with two brown dorsal spines, acutely spinulated, Metathoracic second, seventh, 

 and eighth abdominal segments with large, long tubercles, those on the second ab- 

 dominal segment much the largest, smooth and bearing a rough spinulated spine, the 



Fig. 164. — Limenitis digippus. — After Riley. 



pair on the eighth segment the largest. Body olive-green shading into brown, a lat- 

 eral white irregular line and an irregular dorsal patch on segments 4 to 6: the fifth 

 segment nearly all pearly white. Length SO"^™. (See Fig. 40, p. 129.) 



Pij^ja.— Suspended by the tail alone. Head deeply conical ; a dorsal low thoracic 

 ridge; a very high, thin, compressed rounded smooth ridge on the second abdominal 



5 ENT 29 



