60 The Mechanism of Evolution in Leptinotarsa 



Habitat, Ecology, and Life History. 



As far as known, the life-history of this species is like that of L. muUitceniata 

 Stal. It passes the long, dry, cold winter in the imago stage, hibernating in the 

 ground, emerges at beginning of rainy season in June, breeds by the middle of 

 June, and produces a first summer generation which emerges about the end of 

 July. Then these breed again and give a second generation, which emerges 

 late in August or early in September. This second generation was always 

 observed to be small and was several times apparently absent. In cultures a 

 normal rhythm of two generations in each reproductive cycle was found. 



SoxmcE OF Material. 



The stock for breeding and testing came from the following locations : (a) 

 Toluca, on open plain to south of city, about 1 kilometer south of Capilla de 

 San Sebastian; (&) Mexicalicingo, on open plain near town. 



LEPTINOTARSA DECEMLINEATA Say. 

 (Plate 6, fig. 5; plate 7, fig. 2.) 



Doryphora 10-lineata Say, 1824. Journ. Acad. Nat. Sci. Phila., Ill, pt. 2, 

 p. 453; Rogers, 1857, Proc. Acad. Nat. Sci. Phila., VIII, p. 302; Suffr., 

 1858, Ent. Zool., XIX, p. 244.2; Walsh, 1865, Pract. Ent, I, No. 1; 

 Harold, 1874, Berlin Zeit., p. 444. 



Leptinotarsa decemlineata Gemminger et Harold, 1874. Catalog. Coleop., 

 t. IX, p. 1, p. 3440; Jacoby, 1883. Biol., Centr. Am., vol. VI, pt. 1, p. 233; 

 pi. XIII, fig. 24, suppl., p. 253. 



And many other authors. No doubt is attached to the determination of this 

 form. 



Say's original description is as follows: 



" Yellow ; thorax litterate, with black ; elytra each with five black lines. 

 Inhabits Missouri and Kansas. Body yellow ; head with a triangular, black, 

 frontal spot; thorax two abbreviated black lines, divergent before; about six 

 black dots on each side; elytra, sutures, and five lines on each, black; the 

 interior line is confluent with the suture behind ; exterior line marginal ; three 

 intermediate ones joined or approximated at tip; beneath, incisures and three 

 or four series of ventral spots black. 



" Length two-fifths of an inch. 



" Var. a elytra white ; the two outer, intermediate lines are united at base 

 and tip. 



" This species seems to be not uncommon on the upper Missouri where it was 

 obtained by Mr. Nuttall and myself. The variety I found on the Arkansas." 



Description of Living Animals. 



Imago. — Above: Oval, convex, robust, variable in form, size, and color, 

 depending upon age, geographic location, and conditions of growth during 

 ontogeny; head, epicranium, and pronotum yellowish brown, rarely reddish, in 

 sexually mature specimens, often reddish in freshly emerged specimens, with 

 variable pattern of black spots; epicranium rather uniformly punctate with 

 moderately developed pits, most numerous behind eyes, eyes black, niouthparts 

 yellow brown, rarely black; mandibles black, tips of palpi black, basal joints 

 brownish ; antennse, basal 5 or 6 joints brownish, last 6 broadened, broad as long, 

 black, slightly pubescent, last joint short, conical, often nearly oliscured. 



