KEY TO MATURE LARVAE OF NORTH AMERICAN MALACOSOMA 



(Preserved larvae should be dried off to see the colors properly.) 



1. Middorsal line whitish and apparently continuous, without 

 any obvious constrictions at the intersegmental areas; head 

 black (figs. 350-351) americanum, p. Ill 



Middorsal line absent, or interrupted at the intersegmental 

 areas, or with definite constructions at the intersegmental 

 areas (figs. 339-399, except 350 and 351); if the line is 

 nearly continuous, it will be bluish-white and the head will 



be bluish (fig. 398) 2 



2(1). Middorsal line consisting of a series of keyhole-shaped, 

 whitish-cream marks, one per segment (figs. 339 and 340), 

 sometimes divided to form a larger anterior spot and a 

 smaller posterior spot; rarely only the larger anterior spot 

 is present disstria, p. 84 



Middorsal line present or absent, but without markings like 



those described above 3 



3(2). Middorsal area without a blue-white stripe of any kind on 

 the abdominal segments 4 



Middorsal area with some kind of a blue-white or whitish 



stripe on the abdominal segments 11 



4(3). Middorsal and addorsal areas marked with an hourglass- 

 shaped orange mark on each segment (figs. 345 and 346) ; 

 the "neck" of the hourglass with a round black spot at the 

 anterior edge surrounding the base of setal group Dl; at 

 least some of the setae in Dl blackish; lateral setae 

 distinctly tufted around setal group L2 (figs. 345-348); 

 (on blackish-orange specimens all of these characters are 

 more difficult to see than on bluish-white ones); distribu- 

 tion — California, Oregon, Washington, and Baja Cali- 

 fornia 5 



Middorsal and addorsal areas variously marked, but usually 

 not with an hourglass-shaped mark; if the mark is some- 

 what hourglass-shaped (fig. 392), the black spot surrounding 

 setal group Dl is not round, the setae in Dl are not black, 

 and the locality falls outside the distributional limits given 



above 6 



77 



