DISTRIBUTION OF L. MUI^TlT^^ENIATA. I9 



basins like the Valley of Mexico, where were located great Tertiary lakes 

 which have been filled with sediment and volcanic ejecta until only remnants 

 remain, as, for example, the shallow lakes in the Valley of Mexico. In these 

 lakes various Tertiary land vertebrates have been preserved. Subsequently, 

 the whole area was elevated and the precipitation lessened, and the lakes 

 began to dry up, the volcanic ejecta and the sediment brought down from 

 the surrounding mountain ranges was too abundant to be removed by the 

 streams, and the old valleys became filled up with a thick covering of adobe 

 soil, largely of modified volcanic debris. The area now presents all of the 

 characters of a mountain park or basin. 



This region has served as a second center of dispersal for these beetles, 

 and one in which new forms have originated and are probably now being 

 produced. Beyond doubt multitceniata is the parent form of this group. 



In its habitat multitce7iiata is a typical grassland form, where it feeds upon 

 Solanum rostratum or its allies, and has a much wider habitat than any 

 of the preceding species. It is most abundant about Puebla and in the 

 Valley of Mexico, especially upon the western side ; and it becomes less and 

 less common to the eastward and to the north until it finally vanishes. The 

 food plant is generally distributed, especially about places where cattle, 

 horses, or burros are pastured or in waste places, the seed being carried to 

 these places in the hair of the animals. The general aspect of its habitat is 

 shown in the photograph on plate 5, which shows an almost pure steppe. 



As in the preceding species, the control of the distribution within the 

 habitat is dependent primarily upon moisture which is regulated by soil and 

 the precipitation. The soil conditions demanded are a fine, moist adobe earth, 

 so situated as regards drainage, either by streams, ditches, or a porous subsoil, 

 that it shall not remain saturated with water for any length of time. If the 

 soil remains saturated, or if it dries out too quickly, fatal results will rapidly 

 follow to pupae or aestivating imagines and will produce a high rate of mor- 

 tality, if not complete extinction. Over the Valley of Mexico and about 

 Puebla the optimum conditions are extensively developed, but even in these 

 places the beetle thrives best near a ditch or the edge of a small stream 

 (plate 6), which is cut deep enough so that the danger of overflow is slight, 

 insuring adequate drainage and an abundant supply of telluric water. Over 

 the Plains of Apam the soil conditions are more variable, and, consequently, 

 the distribution is much less uniform than in other portions of the habitat. 

 The hillsides, talus slopes, or water-washed sands are tabooed, as also, to a 

 less degree, the low, marshy areas. The condition demanded for existence 

 by L. multitcBuiata are much like those of the preceding species, but the dis- 

 tribution in isolated colonies is not found. The continuous distribution so 

 characteristic of this species is due to the topographic development of the 

 area in which it lives, which has produced over wide areas the conditions 

 requisite for proper habitat formation. It is of interest to note in connec- 



