The general interest created by destructive grasshoppers in the past few years incited the author to some studies on populations of Orthoptera, particularly on prairie patches in Iowa. Correlations of the data with climatic information will be made at times to yield possibly valuable results

Hendrickson, George O.

English

Name not available

The Effect of Heavy Rains on the Orthoptera (Grasshopper) Population of the Prairie

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 40 Annual Issue Article 138 1933 The Effect of Heavy Rains on the Orthoptera (Grasshopper) Population of the Prairie George O. Hendrickson Iowa State College Copyright ©1933 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Hendrickson, George O. (1933) "The Effect of Heavy Rains on the Orthoptera (Grasshopper) Population of the Prairie," Proceedings of the Iowa Academy of Science, 40(1), 238-240. Available at: https://scholarworks.uni.edu/pias/vol40/iss1/138 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. 238 IOWA ACADEMY OF SCIENCE Hence, x B. V. = P. V. + (P. V. x y); when: -B. V. equals blood volume in liters (x 1,000 for cc.). P. V. equals plasma volume in liters. ~ equals ratio of cells to plasma in the blood. y [Voi:.. XL In the accompanying table the plasma volume and blood volume measurements are given for both single and parabiotic rats. The weights of each member of a parabiotic pair could not be con-veniently determined. so the combined weight is given, and er1ual amounts of dye were injected into each animal. The table indicates that there may possibly be a slightly higher percentage of blood in female than in male rats. The results as a whok show that about one-tenth of body weight is blood. which is slightly higher than given by other investigators. LITERATURE CITED s~nTH, H. P. 1930: Studies on vital staining. II. The removal of Brilliant Vital Red from the blood stream. Distribution of dye between blood stream and body tissues. J. of Expt. Med. 51: 379. ZOOLOGICAL LABORATORY, STATE UxIVERSITY OF lowA, low.\ Cnv. lowA. THE EFFECT OF HEAVY RAINS ON THE ORTHOP-TERA (GRASSHOPPER) POPULATION OF THE PRAIRIE GEORGE 0. HI\NDRICKSON The general interest created by destructive grasshoppers in the past few years incited the author to some studies on populations of Orthoptera, particularly on prairie patches in Iowa. Correla-tions of the data with climatic information will be made at times to yield possibly valuable results. This article will point out that following several heavy rains in August, 1932, the number of grasshoppers had markedly decreased on a one acre plot of Stipa spartca - A11dropogon scoparius association of prairie located 5 miles south of Stanhope and 22 miles northwest of Ames. As the grass had not been grazed, mowed or burned for several years the tract presented a thick cover of protective material. Corn bordered 1Hendrickson: The Effect of Heavy Rains on the Orthoptera (Grasshopper) PopulatPublished by UNI ScholarWorks, 19331933] ABSTRACTS 239 on two sides and Sudan grass grew at the other two sides of the plot. The first collection dealt with in this paper was made on August 8, 1932 at 10 :30 A.~r., with a light wind, nearly clear sky, and an air temperature of near 90° Fahrenheit. The grasshoppers were collected with 200 sweeps of a net over an area of 100 sq. m. During the ten succeeding days, chiefly on August 12 and Au-gust 17, a rainfall of 5.95 inches was measured at the Agronomy Farm of Iowa State College. On August 19, at the same hour of the day as the first survey and with climatic conditions as favorable for grasshopper movement as those of the 8th, a second collection of grasshoppers was made in a manner as before. The species, with numbers of adults and nymphs counted to-gether, that were taken are shown in the following table. SPECIES Cor.u:cn:IJ AUGUST 8 AUGUST 19 Diaphcromcra velcii 4 1 Erotcttix simplex 4 5 OrphulC'lla spccinsa 12 9 Chortophaga zfridifosciata 1 0 M elanoplus dawso11i 4 0 J!. f emur-rubrnm 0 4 M. differcntialis 1 0 Phoetaliotes 11cbrasce11eis 2 3 Scuddcria texensis 1 1 Conoccphalus strictus 11 4 C. sa/ta11s 24 17 Ncmobius fas.ciatus 1 2 Oecanthus nigl'icomis q11adrip1mctat11s 2 1 Total 67 47 It is suggested that the heavy rainfall was the major factor responsible for the approximately 30 per cent decrease in popula-tion during the ten day period. DEPARTMENT OF ZOOLOGY, IowA STATE Cou,ICGE, AMES, IowA. REINFECTION OF RATS WITH EIMER/A MIY AIRII AFTER IM::VIUNIZATION E. R. BECKI~R AND PHOEBE R. HALL It was shown in previous paper ( 1932) that rats which had not previously been infected became immune to Einzcria. miya.irii after recovery from an infection produced by ingesting 1500 oocysts daily for five days. It was also stated that in the passing 2Proceedings of the Iowa Academy of Science, Vol. 40 [1933], No. 1, Art. 138https://scholarworks.uni.edu/pias/vol40/iss1/138240 row A ACADEMY OF SCIENCE [VOL.XL of the weeks some of the immunity was lost. The latter statement was based upon an experiment with four rats which showed the last coccidia on September 25, 1931, and which could not be rein-fected immediately, but which again became infected after ingest-ing large numbers of oocysts on December 12, 1931, - about 78 days after the last oocysts of the first infection were eliminate<l. Three of these rats passed oocysts "in moderate numbers" for three days, but only one oocyst was recovered from the fourth rat. It seemed desirable to repeat the experiment making quantitative counts of the oocysts. The technique for making the counts was the same as that previously described. Ten white rats (Nos. 135 to 144 of the previously published records) each eliminated from 21,560,000 to 103,000,000 oocysts during the first infection, the mean being 53,777,000 oocysts. The elate of the first infective feeding was February 22, 1932, and the last oocysts were eliminated on ?ITarch 7, 1932. Five of these rats were fed 1,500 sporulatecl oocysts of the same parasite daily for five days, beginning May 23, 1932. The drop-pings of these rats were saved for the period from the seventh to the fifteeenth day after the first infective dose. This eight day interval, as experiments with 600 rats have shown, is the period during which the oocysts will be eliminated by this mode of in-fection if the animals become infected. Of the five rats, three did not become reinfected, one eliminated 192,590 oocysts, and t:he other 185, 184 oocysts. Three of the remaining rats were infected on July 15, 1932. One of these could not be reinfected. By the use of the sugar-flota-tion method, one oocyst was recovered from one of the other two, while three oocysts were recovered by sugar flotation from the re-maining rat. The experiment shows that, in certain cases at least, a rat immunized to the coccidium Eimeria. miyairii may lose little or none of its immunity within a period of from 77 to 130 days after its recovery from the immunizing infection. Although quantitative counts were not made upon the rats used in the previously re-ported experiments, the writers had the impression from the num-bers observed in the fields of the microscope that three of the four reinfections were heavier than those here reported. DEPARTMENT OF ZOOLOGY, IowA STATE; CoLLEGB, AMES, IowA. 3Hendrickson: The Effect of Heavy Rains on the Orthoptera (Grasshopper) PopulatPublished by UNI ScholarWorks, 1933

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The Effect of Heavy Rains on the Orthoptera (Grasshopper) Population of the Prairie

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