48 The Mechanism of Evolution in Leptinotaesa 



Stal's description is as follows: 



" Ovalis, nigra ; prothorace Igeviusculo ; elytris testaceo-flavis, minus regu- 

 lariter geminato-seriatim distincte punctatis, margine inflexo, vitta angusta 

 suturali interstitiisque alternis nigris. Long. 9, Lat. 6^ millim. 



"Patria: Mexico (Mus. Holm., Coll. Dohrn). 



"Ovalis, sat convexa, nigra, nitida. Caput parce, subtiliter,punctulatum. 

 Antennae graciles, articulis quinque ultimis subtransversis, clavam sat dis- 

 tinctam formantibus. Prothorax elytris nonnihil angustior, antrorsum sensim 

 leviter angustatus, Isevis, utrimque punctulis raris adspersus, angulis anticis 

 subacutis. Scutellum laeve. Elytra lateribus parallelis, minus regulariter 

 geminato-seriatim distincte punctulata, testaceo-flava, margine inflexo, vitta 

 angustissima suturali nee non vittis quinque, interstitia alterna occupantibus, 

 nigris, vittis basin baud attingentibus, tribus interioribus prope apicem abbre- 

 viatis et conjunctis. 



" J* Segmento ventrali ultimo apice truncato." 



Easily distinguished by black head and pronotum and black ventral surface. 

 Jacoby, 1883, noted that third and fourth elytral black stripes are sometimes 

 imited. This is not common and is due to crossings with another form, 

 tacubayaensis nov. var., and its presence in the strain. The elytral ground-color 

 is variable, dark ocher-yellow, yellow, or red. These differences can be separated 

 in breeding, giving the melanothorax type in four minor biotypes : L. multi- 

 toEniata-melanothorax hi, red elytral ground (plate 4, fig. 6) ; L. muUitwniata- 

 melanothorax hn, orange elytral ground (plate 4, fig. 5) ; L. multitceniata- 

 melanothorax h^, yellow elytral ground (plate 4, fig. 4) ; L. muUitceniata- 

 melanothorax h^, white elytral ground. All of these breed true genetically, and 

 are alternative in their behavior in crossing. (Plate 4, figs. 4, 5, and 6.) 



Food, juvenile stages, distribution, habits, and ecology as in L. multitoeniata 

 Stal. 



Saltation L. multit^niata-tacubayaensis nov. vab. 

 (Plate 4, fig. 3.) 



Like L. melanothorax Stal in size, form, head, and pronotum ; elytra orange 

 or red, with longitudinal stripes, broad brownish black, the first confluent with 

 anal edge, forming large wedge-shaped median stripe, the second broad, united 

 to fused third and fourth stripes posteriorly. Costal edge black, inflexed portion 

 yellow brown and sharply grooved. Impressed punctations, large, 2 to 3 rows, 

 interspaces smooth, arched, conspicuous. Below, all parts shiny black, except 

 posterior and lateral portions of sternal sclerite of abdominal segments. 

 Antennae second and third joints brown or yellowish, remainder black. 



This rare sport breeds genetically true and is in cultures different from 

 L. melanothorax. In nature examples of this form are frequently contaminated 

 by attributes from other portions of the species, but no difficulty is encountered 

 in purifying it and establishing it as a stable, uniform race. 



Food, juvenile stages, habits, and ecology: The same as in general species. 



Geographical distribution: Valley of Mexico; I have found it at Tacubaya, 

 Tacuba, Chapultepec, and Texcoco. 



Further complications are introduced by the presence of a biotype form that 

 occurs in the species and with regularity in some locations, to which I have given 

 Stal's name, L. muUilineata, in that Stal's description fits perfectly the biotype 

 in question. In museum material it is frequently not unlike some specimens 

 of L. decemlineata Say and L. oblongata, but it has no relations to these two 



