36 The Mechanism of Evolution in Leptinotaesa 



Black, joints 7 to 11, broad as long, distinct, terminal joint reduced, conical, 

 posterior portions of epicranium punctate, with large pits. Pronotal color- 

 pattern uniform, spots and central V-shaped spot constant, composed of 



am 

 a'+ "4^ -I- a and a large spot in each outer posterior angle composed of 



pm 

 d'jf-e'+f and d+e+f. Lateral third of pronotum coarsely punctate, middle 

 third polished, few minute pits, scattered larger punctations. 



Size: Larger than L. undecimlineata, Stal and somewhat smaller than L. sig- 

 naticollis Stal. More robust than former, less so than latter. Male 8 to 14.5 

 mm. long, 5 to 7.5 mm. broad; female 8 to 17 mm. long, 5 to 9.5 mm. broad. 



Sexes: Female, sternal sclerite of last abdominal segment rounded, not 

 truncate ; male, same sclerite truncate, with well-marked median groove from 

 posterior border to about the middle of the plate. In general the male is smaller 

 than the female and differs in being narrowed posteriorly, while the female is 

 broadened. 



Food: At Orizaba, Solanum chrysotrichum Schl.; Duges (1883) gives 

 *S^. torvum; Dr. Greenman states that 8. torvum is not found in Mexico; at 

 Guanajuato, on ;S^. hertwigi Bereth ; on west coast, on 8. diversifolium Schl. and 

 S. hertwigi Bereth. 



Juvenile Stages. 



Eggs (plate 1, fig. 10) : Laid on lower surface of leaves in bunches; 20 to 

 300; yellow, oval, ventral surface slightly flattened and concave; attached by 

 stalk of varying length composed of coagulated gelatinous cement. Long, 1.35 

 to 3.5 mm., broad, 0.75 to 1.35 mm. Development requires an average of 8 days 

 under normal conditions ; range 6 to 13 days. Duges records eggs of two sorts — 

 first fixed by foot and second stalked. This difference, which exists in nearly 

 all the species of this group, is, as far as I have observed, due entirely to the 

 manner of laying and the drawing out of the material used to cement eggs to 

 leaf into a longer or shorter attaching stalk. It is not a part of the egg. 



First larval stage (plate 1, fig. 10) : Head, legs, and pronotum, black; body 

 yellow, with full system of spots. Lengbh at hatching averages at end of stage 

 3 to 4.35 mm. 



Second larval stage (plate 1, fig. 11a) : Head, pronotum, and legs, black; 

 body yellow, due to the fact that body has no hyperdermal pigment; spiracular 

 and wing spots only present. Mid-dorsal line and middle of each segment 

 laterally grayish, owing to lack of fat-body in under-lying structures, giving 

 regular pattern of yellow and grayish on back. Length, 4 to 7.5 mm. 



Third larval stage (plate 1, fig. 116) : Head, pronotum, and legs, black; 

 terminal part of legs brown; body yellow or chrome yellow, due to increased 

 density of pigment in fat-body. Second to sixth abdominal segments with 

 broad, tergal black band reaching and often fused with spiracular spots. On 

 first abdominal segment, inner and middle tergals only present, rarely united ; 

 seventh segment, all spots present, variable. Length at maturity, 9 to 31 mm. 

 Coloration of this stage somewhat variable, due to the fusions of the different 

 tergal centers. 



Length of larval life: Varies with condition, but averages 30 days under 

 normal conditions ; range, from 13 to 50 days. 



Pupa: Pupates in ground from 0.5 to 4 inches in depth, at foot of food-plant. 

 Pupa pale yellow, with small spiracula and tergal markings. Pupal stage lasts 

 on an average of 13 days ; range, 8 to 31 days. 



Length of ontogeny: Average 60 days in nature; range, 35 to 70 days. 



