DISTKIBUTION OF THE PARASITES. 



61 



8. THE DISTEIBUTION OF THE PARASITES. 



Parasites of the boll weevil have been recorded from every part 

 of the territory so far invaded. The records are so numerous that 

 we are able to show statistically which are the most important para- 

 sites of the weevil. The following list gives the species in their 

 numerical rank for the entire period from January 1, 1906, to Jan- 

 uary 1, 1910, giving only the number which were accurately deter- 

 mined for each species. The first seven species are the most important, 

 as has been shown in almost every section of this report. The last 

 nine species may be considered as more or less adventitious or acci- 

 dental. These species may possibly never be recorded again, or, on 

 the other hand, they may become in the near future among the more 

 important parasites. This very event has happened in the case of 

 three or four of the other more important species. Up to 1906 only 

 four of the first five in this list had been recorded from the boll 

 weevil. The other species have been added since and some of them 

 will become very important as the weevils enter the moister wooded 

 regions of the East. 



Table XXI. — Numerical rank of the parasites for the entire period, 1906 to 1910. 



Species. 



Microbracon mellitor 



Catolaccus hunter i 



Catolaccus incertus 



Eurytoma tylodermatis 



Cerambycobius cyaniceps 



MicTodontomerus anthonomi 



Tctrastichus hunteri 



Cerambycobius cushmani 



Sigalplius curculionis 



Habrocytus piercei 



Number 



of 

 records. 



2,147 



1,094 



578 



575 



574 



302 



168 



76 



37 



36 



Species. 



Ennyomma gldbosa 



Lariophagus texanus 



Myiophasia senea 



Eurytoma sp 



Cerambycobius sp 



Spilochalcis sp 



Urosigalphus anthonomi 



Urosigalphus sp 



Perilampus sp 



Pimpla sp 



Number 



of 

 records. 



A study of the value of these parasites by years has shown that 

 the majority of the species had not occupied the same rank in two 

 successive years. The accompanying diagram (fig. 13), giving the 

 yearly rank of the boll- weevil parasites from 1906 through 1909, 

 shows that in each year new parasites were recorded and that in some 

 cases these parasites continued to attack the weevil. Microbracon 

 mellitor appears to vary but little in importance in different seasons, 

 while Catolaccus liunteri shows increasing importance year by year. 

 Some of the other parasites of considerable importance appear extremely 

 variable in their relative rank. It will be noticed that Habrocytus 

 piercei has occupied the ninth place three years in succession and 

 is now in eighth place. This parasite occurs in small numbers, but 

 may at any time become a leading parasite in Louisiana and Missis- 

 sippi. In addition to giving the yearly rank of the species this 

 diagram also shows the proportion of the sexes observed each year. 





