358 PRINCIPLES OF SOIL MICROBIOLOGY 



insects in the upper nine inches of an acre of unmanured plot and 

 7,727,000 in a manured plot. The dominant groups in both plots 

 were the Collembola and Formicidae; the Chironomidae larvae and 

 Trichocera larvae were much more abundant in the manured plot. 

 The Collembola were represented by 14 species: the Thysanura by 3 

 species, the Orthoptera and Thysanoptera by one each; the Hemiptera 

 by 4; the Lepidoptera by unidentified larvae; the Coleoptera by 30 

 species; the Diptera by 7 species and various unidentified larvae; 

 the Hymenoptera by 10 species. The greatest majority of the organisms 

 were found in the upper three inches of soil. The wireworms attain 

 a maximum at a depth of 5 to 7 inches. Manuring increases the total 

 number of soil organisms about 200 per cent, but has no appreciable 

 influence on the number of wireworms. 



Morris also found 3,586,088 insects in an acre of permanent pasture, 

 the numbers of the different orders being Collembola- — 566,680, Rhyn- 

 chota — 15,140, Thysanoptera- — 43,258, Lepidoptera- — 15,140, Coleop- 

 tera— 744,038, Diptera— 2,193,180, Hymenoptera— 8652. Among the 

 injurious insects, the following were found per acre: Agriotes — 

 114,643 larvae and 8652 adults, Triphaena pronuba- — 4326 larvae 

 and pupae, Tipula oleracea and T. paludosa 19,466 larvae. The 

 family most represented was the Bibionidae, the species of this family 

 making up 32.4 per cent of the total number of soil insects; Myceto- 

 philidae was represented by 16.7 per cent and Staphyinidae by 12.2 

 per cent. The Coleoptera were represented by 29 species. According 

 to Thompson, the orders Collembola and Acarina determine the trend 

 of the total fauna curve, since they are the dominant groups. They 

 persist throughout the year, while other groups like the Nematoda and 

 Oligochaeta may be entirely missing for varying lengths of time. Cul- 

 tivated land contains a considerably smaller population than pasture 

 or grass land; the maximum population was found to occur in the 

 winter months, due to sufficient moisture in the soil. Peat soils also 

 contain a definite fauna of insects, as represented by the Collembola. 47 

 M'Atee 48 reported the presence of 1,216,880 animals belonging to In- 



wiss. Insektenbiol., 6: 1-4, 44-57. 1910; Adams, C. C. An ecological study of 

 prairie and forest invertebrates. 111. State Lab. Nat. Hist. Bui. 11: Art. 2. 

 1915; Shelford, V. E. Animal communities in temperate America. Geogr. Soc. 

 Chicago, Bui. No. 5; Univ. Chicago Press. 1913; Vestal, A. G An associational 

 study of Illinois sand prairie. 111. State Lab. Nat. Hist. Bui. 10: Art. 1. 1913. 



47 Handschin, E. Beitrage zur Kenntnis der Collembolefauna der Hoch 

 moore Estlands. Beitr. Kunde Estlands., 10: 167-176. 1924. 



48 M'Atee, W. L. Census of four square feet. Science, N. S., 26: 447-449. 

 1907. 



