308 The Mechanism of Evolution in Leptinotaesa 



far seen. Biotypes 10, 11, and 12 are entirely absent, but a new line of arrange- 

 ment is introduced in this form that is represented by biotypes 13, 14, and 15; 

 pattern arrangements that were not present in the population of the first species. 



ADDITIONAL PRIMARY BIOTYPES. 



Biotype 13 : A condition of the pattern in which the marginal elements are 

 all wanting; the areas much reduced with the fusions a' + a and d + e the 

 only ones present. There is also a reduction of the anterior a center and a 

 widely divergent axis of the a, the spot giving them a sharp broad V-shape that 

 is quite distinctive and unlike anything seen in L. multitceniata. Biotype 14 

 is in most respects like 13, with the exception that the a spots are parallel and 

 fused along their entire median sides, giving a central oval or oval spot notched 

 at the ends. This biotype is also distinctly separated from the others by the 

 absence of spot c. Biotype 15 differs from all of the rest in the complete lack of 

 any permanent associations between the elements of the pattern and the 

 tendency to reduce the areas into their component elements where compound. 

 The a areas are often separated, and the e areas are divided into a three-lobed 

 area or into three isolated centers. Considerable somatic disturbance occurs in 

 this pattern and often obscures the true condition in the system, as is shown in 

 the figure, where the member of this biotype nearest to 13 and 14 shows the a 

 areas fused, when in reality such an individual would not breed as such. 



The two species then present 16 biotypic conditions that can be analyzed out 

 of the populations, that are capable of being isolated, breed true, and act when 

 crossed as alternatives, giving in Fj a segregation into the same extracted bio- 

 types. There is one conspicuous difference between the condition in L. mul- 

 titaniata and undecimlineata, namely, that in the first the entire range in the 

 character may be present in the population at one location, as it was at Chapul- 

 tepec on certain occasions, while in L. undecimlineata the entire known 

 range of the system is never exhibited by the population of any location 

 at one time or through any length of time ; and furthermore, the different bio- 

 types have a geographical distribution in the habitats occupied by this species 

 that is interesting and would have been of interest to have followed in a series of 

 locations had this been practicable. The difficulties of transportation in the 

 southern portions of the range inhabited by this species, from the Rio Coatza- 

 coalcos and southward, made any project of this sort out of the question. Had 

 such been possible, it is certain that the results of the examination would only 

 have shown the same principles found in the locations that could be followed 

 with ease, and have added perhaps instances of localized distribution of some 

 biotypes, a condition that has little interest to us, and no possibility of solution. 

 The fact that biotypes may be geographically limited is at least interest- 

 ing and suggestive of another productive cause of heterogeneity in nature. 



Two locations were chosen for examination of this species in the savannahs of 

 lower Vera Cruz, on the Vera Cruz al Pacifico Railroad, that were comparable 

 but different in topography and in the environmental complex, as far as it is 

 possible in the savannah areas. These locations at Tierra Blanca and San 

 Marcos have already been described in Chapter II in the description of the 

 habitats and the sources of the material that had been used in the experimental 

 work. No records of the climate for either place are available that are of any 



