percentage of rosette stage plants occurred at Neihart 

 (83%) , and reduced percentages were observed at Kings 

 Hill and Russian Creek, (71% and 64%, respectively) . 

 From plot data, flowering Cirsium longistylum plants 

 produce from 10 to 16 heads per plant. 



In order to better understand the effect of the 

 infestation of the weevil Rhinocyllus conicus on C. 

 longistylum populations, five C. longistylum plants 

 were were collected from each of five locations. All 

 the heads from each plant were dissected and scored for 

 presence or absence of the weevil. The plants 

 contained a total of 366 heads, 225 of which contained 

 one or more weevils. Thus, an average of 60 percent of 

 the heads on an individual plant were infested. It is 

 not known how this affects population size 

 fluctuations. Monitoring data indicate that 

 populations contained a good mix of both young and 

 adult plants. It is possible that infestation rates 

 are not high enough to limit this species, or that the 

 Cirsium longistylum populations have very few predatory 

 fauna. 



Further studies should focus on the systematic status 

 of C. longistylum , including the possibility of 

 hybridization threats. Additional information is also 

 needed to determine the range of C. longistylum in 

 central Montana, and to assess the possible effect of 

 the weevil infestation on these populations. 



