412 Illinois State Laboratory of Natural History. 



abundant parasites, and also the maximum, minimum, and 

 average number of these parasites found in the hosts. The 

 frequency of occurrence of any one of these parasites in 

 relation to the total infestation of a species is to be learned 

 by a comparison of Tables III. and IV. Thus in a total of 

 fifteen hundred and seventy-seven examinations, — in which 

 seventy-four per cent, were in some measure infested (Table 



Table IV. Comparison of Infestation by Different Parasites. 



host SPECIES. 



Names. 



Quadrula uiultiplicata. 

 tuberculata. . 

 metanevra.. . 

 Jachrymosa. . 

 asperrima . . , 



pustulata 



pustulosa.. . . 



plicata 



trigona 



rubiginosa 





ebeiia 

 Unio gibbosus 



coraplanatus 



Alasmodonta confragosa. 

 complanata 

 rugosa 



marginata. 

 Stropbitus edentulus. . . . 

 Anodonta imbecilis 



suborbiculata . 



corpulenta 



ObHquaria reflexa 



Plagiola elegans 



donaciformis.. . . 

 Lampsilis parvus 



ellipsis 



ligamentinus. . 



luteolus 



anodontoides . 



rectus 



ventrioosus . . . 



alatus 



gracilis 



Totals 1577 41 



2S 

 41 

 36 

 29 

 21 

 20 

 87 

 89 

 27 

 40 

 23 

 35 



137 

 35 

 64 

 18 

 51 

 36 

 49 

 20 

 45 

 32 

 48 

 37 

 31 

 11 

 91 

 25 

 62 

 49 



108 

 60 

 89 



Percentage of 



hosts infested 



with 



CD Oi 



r 1 o 



tiq 



P 



CO 



11 



80 

 33 

 72 

 100 

 25 

 32 

 70 

 11 

 25 

 30 

 26 

 27 

 26 

 16 



18 

 17 



51 

 100 

 82 

 9 

 03 

 57 

 65 

 86 



i2 



76 

 14 



28 

 82 

 87 



o 

 o 



29 

 3 



55 

 11 



15 



14 

 35 

 90 



88 



7 

 79 

 14 

 16 

 29 

 43 

 22 

 45 

 52 



18 



11 

 56 

 33 

 24 



44 

 80 

 57 

 40 



3 

 1 

 3 



33 

 50 

 76 



8 

 20 

 75 

 71 

 41 

 83 



3 



7 

 22 

 48 

 61 

 65 

 67 



Number of 



parasites in 



one host. 



r> o 



P 



00 



.> 



1!) 



6 



41 



L3 



5 



5 



-20 



6 



6 



•24 



■7 



28 



75 



85 



o 



p 



en 



1-7 

 1-2 



-6 1-2 



1- 



1 



1 



1 



I 



1 



1 



12 



10 



9 



37 



50 



1 



-6 



7 



26 



63 



i 



33 



5 



134 



63 



80 1 

 64 1-77 



37 



L- 



1-2 



1-7 



1-86 



1-92 



1 

 1-5 

 1-8 

 1-5 

 1-6 

 1-9 

 1-15 

 1-10 

 1-12 



1 I 



1 



1 



ggs 

 -6 



3 

 -7 

 -22 



4 



4 



8 



12 



20 



9 



His 



31 



Average No. of 



parasites in 



one host. 



CO o, 

 T> O 



OS 



p 



2 



6 



2 



12 



6 



2 



2 



4 



3 



4 



6 



2 



3 



27 



11 



3 

 3 

 3 



13 

 8 

 1 

 4 

 2 

 5 



14 



1 



6 



2 



18 



16 



15 



a 

 o 



p 



CO 



1 



2 



3S 

 12 



1 

 23 

 2 

 2 

 2 



2 

 3 



6 



1 

 1 



Eggs 

 1 

 2 

 3 

 8 



Eggs 

 3 

 8 

 2 



2 



1 



4 

 2 

 3 

 4 

 3 

 3 

 50 



