Hubert M. Morris 295 



ARACHNID A. 



Areinida. Porrhomma pygmaeum Pd. 3 ( j^^ ) ; Centromerus bicolor Bl. 3 | ^^^ ) ; Trochosa 



terricola Thor. 8, 9 ( y ) ; Stemonyphantes Uneatus L. 10 I ynpr ) ' Linyphia spp. 9 ( t ) • 



Acarina. Anystidae. Anystis baccarum L. 6 | ) . 



/ 14 9\ 

 Gamasidae. Gamasus magnus Kr. 1, 3-G, 9-12 ( :jr-YYj; ^ I; Gamasus sp. (immature) 



3, 4 f ^ j ; Pergamasus crassipes L. 6, 10 ( j— rri ! T ) ' ''''■ ^^'^^^^P^^ ^ar. longicornis 2, 10 



( T-jT ' T ) ' •'*• ''^^^i^ionalis Berl. 11 ( yt ) ! P- hamatus Koch 6 ( y-^ J ; P. septrionalis Oud. 



6, 9, 12 I Y ) ; -^- rumiger Berl. 5, 10 ( y ) ; Pergamasus spp. (immature) 3-11 ( T~f(T ; j-^ ) • 



OLIGOCHAETA (TemcoZae) 1-12 fj^^,: ^V 



\l-\ Iiy 236 7'>\ 



OLIGOCHAETA {Limicolae), NEMATODA, etc. 1-12 (y^^; ,^\. 



'10 '^N \1— V 111/ 



ISOPODA 1, 3, 9-11 i~; ^j 



10 3 

 GASTROPODA 1, 4, 10, 11 (j4jj; \ 



Silvanus surinamensis L., which is recorded in the foregoing lists as 

 having occurred once in the soil from each plot, is an introduced species 

 which is usually recorded as having been found in stored foodstuffs, 

 although Fowler (4) states that it has been taken under the bark of trees 

 in Yorkshire, Epping Forest and Scotland. It seems doubtful if the 

 specimens met with in the present instance could have been living in 

 the soil; they may possibly have entered the soil in the laboratory before 

 it was examined. 



9. Census of Control Plot. 



The total number of invertebrates found in plot 3, in twenty-three 

 samples, was 1471 or 4,952,857 per acre. Of these 735, or 2,474,745 per 

 acre, were insects. 



The numbers per acre of the more abundant groups were as follows: 

 Oligochaeta {Limicolae), etc., 794,612; Collembola 693,602; Formicidae 

 690,235; Diplopoda 595,959; Oligochaeta (Terricolae) 457,912; Acarina 

 215,488; Chilopoda 215,4:88. The numbers of insects belonging to groups 

 recognised as pests were: Elateridae (larvae) 164,983; Hepialidae (larvae) 

 23,569; and Tipulidae (larvae) 16,835. The numbers per acre in the 

 different orders are shown in Fig. 5. 



The "probable error" in the total population per acre is ± 520,000, 

 and in the number of Elateridae larvae per acre ± 44,000. 



The number of species of insects which occurred in the samples was 

 about 60 but, as in the other plot, this number might have been higher 

 if all the larvae could have been exactly determined. 



