r.»-"] ECONOMIC ZOOLOGY — ENTOMOLOGY. 553 



The decay of wmul liy 7'. iKirtKtniciiiis consists of a series of cheniical and 

 jtiiysical chancres ImiuKlit about by the reduction of the woody substance by 

 enzyui secretions. The dissolution of the cell walls is attributed to the fact 

 tliat they, as a rn^tential source of food, are valueless to the fungus until 

 broken down and reduced to a condition suitable for translocation and assimila- 

 tion. The enzymatic dijiestion <uul consequent decay of wood is accomplished 

 mainly by the exceediiit,dy minute funeral hyi)ha\ the ultimate branches of the 

 mycelial system. 



Decay by this si>ecies is characterized by its habitual tendtuicy to produce a 

 minute pocket type which becomes a conspicuous feature in the later stages 

 (.r the disease. The first chemical change brought about by the action of the 

 fungus is that of delignification. 



The results obtained from the study of the decay caused by this fungus 

 .-■laldish the fact that the minor variations in the decay of different woods 

 are nuich more dependent upon the dissimilar structures of the respective 

 woods than has been generally supposed. Anatomical and microchemical ob- 

 servations on the decay of the five woods studied indicate that the vegetative 

 mycelium of P. pargamenns secretes diastatic, proteolytic, and cytohydrolytic 

 enzyms, among the latter being pectinase, cellulase, and ligninase. 



The practice of allowing fires to run through hardwood forests furnishes 

 favorable conditions for the entrance into wounds of this and other sap rot- 

 ting fungi. 



The incubation period of P. imrt/aiiicnus under conditions studied was less 

 than 15 months and appi'ars to be more nearly 12 months. In case of artificial 

 cultures the length of the entire life cycle varied from 4 months in agar plate 

 cultures to 18 months in cultures on blocks of wood. 



ECONOMIC ZOOLOGY— ENTOMOLOGY. 



Field experiments on the cheniotropic responses of insects, A. D. Imms 

 and AL A. Husain {Ann. Appl. Biol, 6 {1920), No. 4, pp. 269-292, fig. 1).— The 

 most noteworthy features of the experiments here reported have been sum- 

 marized as follows: 



" The experiments were conducted during July and August, 1918, and for the 

 most part during wet and apparently unfavorable climatic conditions. The 

 insects attracted consisted almost exclusively of Diptera. With the exception 

 of one or two examples of Vespa vulgaris, no Hymenoptera responded. Kyn- 

 chota, Coleoptera, and Neuroptera (sen. lat.) were unrepresented. A small 

 number of Noctuid Lepidoptera entered the traps, but for the purpose of con- 

 ducting experiments with such relatively large insects as many Lepidoptera it 

 Would be nece.ssary to alter slightly the construction of the traps used in order 

 to allow of greater facilities for ingress. 



" Beer, cane molasses, and mixtures of these two substances are powerful 

 cheniotropic agents for various Diptera. Ethyl alcohol, in various concentra- 

 tions, exhibited little or no cheniotropic properties, but with the addition of 

 small amounts of butyric, valerianic, or acetic acids it exercised a powerful 

 stimulus. Acpieous solutions of the above acids were not attractive, the respec- 

 tive esters prohal)ly being the attractive agents in each case. The remaining 

 substances utilized in these experiments were found to exhibit little or no posi- 

 tive cheniotropic properties. 



■'Out of considerably over 3,(XX) Diptera attracted during the course of these 

 ob.servations, by far the greater number pertained to one or other of the five 

 faluilies Khyphidie, Mycetophilida;, Sepsida}, Muscidae, and Anthomyidse. As a 

 general rule members of both sexes of a species were attracted irrespective of 



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