Analysis of Hbteeogeneitt m the Population 



309 



value in this connection, and the few measurements and the maxima and minima 

 that I obtained are not of any significance in this connection. 



THE TIERRA BLANCA COLONY. 

 Eleven censuses of the population were made at this point, beginning in 1904 

 and ending in 1909. These probably do not represent as purely generation 

 determinations as do those for muUitceniata, owing to the fact that the species 

 breeds over a longer time than the former, and that the generations become 

 much mixed from the middle of the summer on, and in nature the population is 

 mixed with respect to the number of generations in the yearly cycle. In captiv- 

 ity in pure lines the cycle in my cultures has been uniformly two, with a period of 

 rest between that varies with the conditions of the medium and the stock. In 

 nature the population is immensely diversified in this character, and stock from 

 nature is heterozygous, giving all sorts of combinations at the start, so that the 

 censuses taken here represent censuses of the natural population, in which the 

 relations of generations to one another and to the censuses could not be deter- 

 mined with accuracy. This condition will not invalidate the general results 

 that may come from the examination of the materials, and will give data on the 

 species comparable with that already obtained. 



Total 1201. 



Fio. 113. — First census of condition in the population at Tlerra Blanca In 1904, 

 sbowing the pronotal pattern. 



68— 



««*• 



«l* 



\ —92 



76 



*■"* V, 109 



51- «(ip 

 108— ^^,j , r--74 



«^ fOh 'yTj -95 



/ 



y* 



V'- 83 



29 46 \ \ 



522 Males. Total 1104. 582 Females. 

 Fig. 114. — Second census at Tlerra Blanca In 1904. 



I^ 



•59 



The first census of 1904 showed in both sexes a uniform population, centered 

 mainly in biotype 7, with indications of 5, Ga, 8, and 9 poorly developed, and no 

 isolated groups of any sort, and on the whole an extremely uniform set of indi- 

 viduals and homogeneous in the total mass of the population. The second census 

 showed essentially the same condition in range and in the biotypes present, the 

 chief difference being the increased development of 8. As far as I could observe 

 and determine from the data to be obtained, the conditions of the climatic com- 

 plex had been favorable to the colony in the year ; at least no striking adverse 

 conditions had been present. The records of the population at the two censuses 

 are shown in figiires 113 and 114. 



