NYMPIIALINAE : BRENTIIIS MYRINA. 599 



the parenchyma of the upper surface of tlie leaves ; at a hiter period it 

 bites lioles entirely through them. It moves very slowly at first but soon 

 learns to wander about with great agility ; it produces little silk, dropping 

 quickly, when disturbed, without spinning a thread. 



Life history. This insect passes the winter as a caterpillar, sometimes 

 just from the egg, sometimes when half-grown. As a result of this dif- 

 ference in age, the first brood of butterflies straggles on in the spring 

 instead of bursting upon us in swarms as is the case with some other 

 species. The l)utterfly usually appears toward the end of May, or consid- 

 erably later than its congener B. bellona, but appears to vary somewhat 

 with the latitude, and especially with the year. The earliest record I have 

 of its appearance is on the l(5tli of May at Albany (Lintner), where it is 

 then even reported as abundant. I have myself seen it at the same place 

 on the 17th. It is reported from as far north as Ottawa on the 22d, while 

 the first specimens seen in their respective localities were found in other 

 years at New Haven and Boston on the 24th, about Boston on the 27th, 

 28th and 30th ; in two separate years Mr. Saunders first found it at 

 London, on the 4th of June. Gosse notes its first appearance in Comp- 

 ton as late as June 10, and Professor Hamlin found it in one year for the 

 first time on the 12th of June at Waterville, Maine. Its usual appearance 

 about Boston is in the early part of the last week in May and it becomes 

 abundant early in June, and flies until the next brood of butterflies has 

 made its appearance. Fresh specimens continue to emerge from the chry- 

 salis throughout June, and in such northern regions as the White Moun- 

 tains and in Maine early in July. The eggs are laid throughout the last 

 half of June and during July, the earliest records being June 15 at Boston, 

 16 at London, Ontario, and 20 at the Catskills. The eggs hatch in six 

 or seven days though sometimes delayed for nine or even ten days. The 

 caterpillars feed for a month, and a new brood of butterflies appears in the 

 latter part of July, rarely before the 19th or 20th (excepting in southern 

 localities like Nantucket, where occasionally they appear as early even as 

 the 3d of the month, thus completely overlapping in time the later indi- 

 viduals of the brood, a couple of hundred miles to the north), and becomes 

 abundant at the end of the month, continuing to emerge from the chrysa- 

 lis throughout a part of August, and being found upon the wing in Sep- 

 tember, when the butterflies of the third brood have made their appearance ; 

 thus repeating the phenomena of the second brood. The eggs of this 

 brood, being often laid immediately upon eclosion of the buttei-fly, may 

 be found throughout the latter half of July and the early part of Auo-ust, 

 and being also found undeveloped in some until the butterfly has flown for 

 some time, are also laid throughout the latter half of August and in Sep- 

 tember. Whether any or many of the caterpillars become lethargic when 

 half-grown is not known : none have been observed bv Mr. Edwards in his 



