28 The Mechanism of Evolution in Leptinotarsa 



specimen labeled, " muUilineata Stal," with the pin labels, " named by Stal," 

 "Type Stal 176," which is evidently an immature specimen, the elytral stripes 

 being brown instead of black. It has, however, the characteristic dark legs and 

 ventral surface and the narrowed pronotum, with the same type of pattern, and 

 in all respects it agrees with the form that I have called " biotype " ^nultilineata 

 Stal, and I think that there is little doubt that muUilineata Stal is a biotypic 

 form of multitceniata Stal, and that oblongata is a distinct species. 



There are in the British Museum five specimens, all alike, that are clearly 

 the same as the oblongata recognized here, and that are labeled midtilineata. 

 Two are from " Oajaca, Mexico," one from the " Baily coll." " Mex.," one with 

 no locality, and one that is marked " muUilineata, agrees well with descrip- 

 tion." All of these are, however, clearly oblongata and not the biotypic form of 

 multita;niata Stal, here designated as muUilineata. 



The species decemlineata Say and multitceniata Stal, are in all respects so 

 distinct that there is no need for confusing them, excepting in very badly pre- 

 served museum materials. There is not the least doubt in my opinion that Stal's 

 species muUilineata is a biotype of his distinct, widely distributed species 

 multitceniata; that oblongata is a distinct species, as is decemlineata Say, 

 although the three are badly confused in all collections and in the taxonomic 

 literature of this genus, and this is especially true of Jacoby's determinations of 

 these species, as shown by an examination of his materials deposited in the 

 British Museum. 



Similar difficulties are encountered in the case of L. dejecta Stal. The t}'pe 

 of organism which has been designated L. dejecta Stal by most of the American 

 writers, and so labeled in collections, is a close relative of L. juncta Guer., has 

 been described as L. texana by Schaffner, and apparently represents a modifica- 

 tion of L. juncta Guer., which has arisen on the semiarid plains of the Rio 

 Grande Basin and nearby areas. Of L. dejecta Stal I have had live materials 

 from Brownsville, Texas, and it is clearly closely allied to L. juncta Guer., and 

 its geographic variety texana Sch. is apparently rare and may be only a rare 

 sport from texana Sch. At least, I do not know that it anywhere exists as a 

 constant, genetically perpetuated member of the fauna of any locality. Stal's 

 original statement that its habitat is " Mexico, Texas, and Yucatan " gives 

 nothing upon which one could base an opinion, and furthermore, his description 

 and Jacoby's figures are not very illuminating. 



The " dejecta " which I have used in my experiments is not the L. dejecta Stal, 

 although so labeled in most collections, but is L. texana Sch., which is not a 

 variety of L. decemlineata as Schaffner supposes, but is related to L. juncta 

 Guer. as shown by the character of the elytral punctation. 



The lineata group represents a homogeneous assemblage of species centering 

 about the lower end of the Mexican Plateau and presents three main trends of 

 evolution, and from present knowledge may be grouped into three divisions as 

 follows : 



Tlie species L. panamensis n. sp., L. guatemalensis n. sp., L. undecimlineata 

 Stal, L. diversa n. sp. (habitudinal variant rugosa n. var.), L. angustovittata 

 Jacoby, and L. si,gnaticollis (biotype nigropunctata Sturm) represent a group 

 entirely confined to the grasslands below frost-line, as shown in plate 3, a 

 tropical savannah group, and all feed upon perennial solanums of the species 

 8. lanceolatum, S. liegerii, S. chrisotrichum, and allied species. 



