42 The Mechanism of Evolution in Leptinotaesa 



There is no difficulty in the recognition of this species, even in badly pre- 

 served museum material, but the variety nigropunctata Sturm, is a biotype, 

 breeding true in its distinctive character, and behaves as an alternative domi- 

 nant character in heredity. Stal's description of L. signaticollis (Monog. 

 Chrys. Am., p. 163), is as follows: 



" Nigra, supra sordide fiavescens ; maculis prothoracis capiteque nigris, hujus 

 vittis duabus flavis; elytris subvage nigro-punctatis, vitta angusta suturali 

 margineque inflexo aeneo-nigris. Long. 12, Lat. 7 millim. 



"Patria: Mexico. (Mus. Holm., Coll. Dohrn). Ovalis, sat convexa, nigra, 

 nitida. Caput parce punctulatum, vittis duabus obliquis maculisque duabus 

 minutis ante medium sordide flavis. Antennae articulis quinque ultimus leviter 

 transversis, clavam minus distinctam formantibus. Prothorax sordide fiaves- 

 cens, elytris nonnihil, angustior, lateribus parallelis, antice angustatus, disco 

 parce, subtiliter, utrimque paullo densius et distincte punctatus, litura media 

 ut littera V formata maculisque lateralibus pluribus, plus minus confluentibus, 

 nigris. Scutellum Iseve, nigrum. Elytra lateribus parallelis, dilute sordide 

 fiavescentia, vage distincte nigro-punctulata, punctis hie illic in series dispositis, 

 vitta angusta suturali margineque inflexo aeneo-nigris." 



This description applies very well to the dead dried specimens of collections. 

 The following description is from living material in all stages : 



Imago (plate 2, fig. 1). — Above: Hypodermal color of head and pronotum 

 pale grayish white, often pale yellowish ivory-white, becoming darkened with 

 age; elytra, pale gray or pale gray-green. Head, mouthparts black; antennae 

 black, terminal joint truncate, eighth to eleventh thickened, broader than long. 

 Epicranium with anterior lateral epicranial spots fused medianward to form 

 heart-shaped spot, and prolonged caudad to fuse with posterior lateral epicranial 

 spots, which are united mediad. Posterior border and lateral portions of epi- 

 cranium behind eyes irregularly punctate with fairly well marked pits. Eyes 



am 

 black. Pronotum with variable pattern of black spots. h' + a'+ -f +a+b 



pm 



are always fused to form widely open V-shaped median spot, c' and c always 

 free, and d, e, f groups somewhat variable. Margins, especially anterior lateral 

 portions, punctate, with well-defined pits ; central portion with few minute pits 

 irregularly distributed. Elytra with black anal edge giving median black stripe 

 when closed. Each elytron with ten irregularly placed double rows of pimcta- 

 tions, marking position of chitinous columns between elytral lamellae, and with 

 slightly variable amount of black pigment in bottom of each pit. These rows 

 are arranged in a definite pattern shown in plate 2, figs. 1 and 2. Under wings, 

 pale yellowish brown, transparent, darker towards the base. The adult colora- 

 tion is not attained until about the third day after emergence. 



Size: Male 7 to 13 mm. long, 6 to 7.5 mm. broad; female 7.5 to 14.5 mm. 

 long, 7 to 9 mm. broad. 



Sexes: Female with sternal sclerite of last abdominal segment roimded ; male, 

 same sclerite sharply punctate, with median groove reaching nearly to anterior 

 border. 



Food: At Cuernavaca, Solarium hertwigi Bereth., S. diversifolium Schlecht. 

 At Atlixco and Matamoros, S. diversifolium and S. lanceolatum Cuv. Will also 

 feed upon S. chrysotrichum Schl., but will not eat S. torvum from the Antilles. 

 Identification of food-plants by Dr. Greenman. 



