THE UN IVE RSIT Y OF MICHIGAN COLLEGE OF LITERATURE, SCIENCE, AND THE ARTS Department of Zoology Final Report BFR.S AND POLARIZED LIGHT Edward R. Baylor Oceanographic Institute, Woods Hole, Mass. Frederick E. Smith The University of Michigan ORA Project 03388 under contract with: DEPARUMENT OF THE NAVY OFFICE OF NAVAL RESEARCH CONTRACT NO. NONR 1224((05) WASHINGTON, D.C. administered through: OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR April 1961

\I ~~N~"I. 0, n,; y.

Von Frisch (1952, et al.) has demonstrated beyond doubt that bees can orient to the plane of polarization* of diffuse incident light. This ability is expressed in their dances, in which bees communicate to one another the direction of a food sources By using a piece of sky and altering its plane of polarization with a sheet of polaroid., von Frisch shows that the bees behave as though they read the sun to be approximately at right angles to this planeo Since von Frisch first demonstrated this phenomenon, orientation to polarized light has been observed in other arthropods by a number of people, including the present authors. After working with polarized light and a variety of aquatic arthropods for several years, we developed certain ideas regarding the underlying mechanism for detection, and eventually reached the point where we had questions to ask the bees. For these purposes a simple experimental design was necessary, in which bee behavior could be studied under a variety of conditions not always amenable to such complex behavio~ as bee language. Hence, a simple test was designed which could be applied to bees caught at random around the laboratory with a reasonable assurance of appropriate performance Bees, like many other arthropods, are usually positive to light when placed in a dark chamber. In these experiments bees were placed in a dark chamber 10 inches square and 1/4 inch deep (inside dimensions), and covered with clear glass. The chamber was placed in a darkroom and illuminated from above with a slightly divergent beam of white light of about 12-foot-calndles intensityo One bee was used at a timeo It could see only the overhead light and various reflections. The latter were reduced as far as possible. The floor of the chamber was a very black, dull paper; its sides were not only black but were shaded by black tape on the glass cover; the entire apparatus was abundantly shielded with black cloth, An introduced bee usually did one of three things: it walked or ran rapidly back and forth as though trying to get out, it groomed itself, or it went to sleepo Data were collected only in the first instance, which occurred about one-third of the time. When a polaroid was placed in front of the light, it was evident that bees tended to run back and forth at right angles to the plane of polarization, with occasional runs in other directions and a considerable amount of running along the edges. To score this behavior, two sets of lines at * Ioeo, plane of vibration of polarized light as checked by the use of a reflecting surfaceo 1

right angles to each other were added to the glass cover. One observer counted how often the bee crossed the lines of one set, while the other counted how often it crossed the lines.of the other set, so that the bee path was analyzed into two vectors (left-right and front-rear)0 The lines of a set were one inch apart, and to eliminate the edge effect all lines ended one inch from the edge. Once the bee was running well, a timer was started and both observerscounted for a fixed time interval, usually two minutes. This was usually repeated, resulting in several trials for each bee. Results are shown in Table I. TABLE I. RESULTS WITH BEES ON DULL BLACK PAPER Data represent inches traveled in two vectors at right angles to each other during the same time interval. Within bees, variations between trials are not greater than random. Bee Trials 1 2 3 1 2 3 4 No Polaroid.70'* 69* 77* 57* 30* 35* 48* 47* Polaroid = 8* 25* 22* 43* 8* 15* 34 75 Polaroid I 12* 9* 111 38 81 37 Total 225 208 72 158 204 84 1 182 186 74 75 191 128 2 114 87 99 119 177 114 3 88 10o4 Total 296 273 261 298 368 242 1 93 77 57 111 119 55 2 69 75 539 95 99 45 Total 162 152 96 206 218 100 1 38 45 56 75 81 42 2 57 52 52 31 Total 95 97 56 75 13355 7 1 92 86 52 84 50 22 2 66 60 33 42 33 22 Total 156 146 85 126 5 44 4 5 * Bee was upside down throughout reading~ 2

In this first experiment the performance was first recorded without a polaroid, and then with the polaroid in two positions (parallel to each of the two sets of lines) so that accidental asymmetries in the environment could be ruled out. In the absence of a polaroid the two vectors werenearly equal, with some tendency to go left and right. With a polaroid the major vector was at right angles to the plane of polarization. (The position of the polaroid is indicated by the parallel lines in the column headings.) Variations from one trial to another for the same set-up and same bee are not greater than random, One bee did most of its running upside down on the glass cover, and as shown it oriented about as well as the others. This was also true of later experiments. Such evidence argues against the ocelli as sources of information for this orientation. On Table II the totals for each bee are reduced to percentages. Differences between bees are greater than random, showing that different bees orient to different degrees. The average for these five bees shows almost a 2-to-l ratio for the vector at right angles to the plane of polarization, The slight tendency to travel left and right without a polaroid (51.4%) is significant, and this bias is apparently additive to the effect of the polaroid, for the two positions have significantly different effects (66.0% and 61.4%). TABLE II. PERCENTAGE OF THE TRACK IN EACH OF THE TWO VECTORS, BASED ON THE TOTALS FOR EACH BEE FROM TABLE I Differences between bees are much greater than random when a polaroid is used. Bee No Polaroid Polaroid Polaroid.ll Avg to Polaroid 1 52 48 31 69 71 29 70.0 3- 0.0 2 52 48 47 53 60 40 56.5 - 43.5 3 52 48 32 68 69 31 68.5 - 31.5 4 49 51 43 57 65 35 61.0 39.0 5 52 48 40 60 65 35 62,5 37.5. Avg. 51.4 48.6 38.6 61.4 66.0 34 63.7 36.3 Considering 'that bees must turn around frequently, and that they seldom run back and forth over exactly the same strip, these vectors have practical limits such that maximum orientation would not produce a ratio of 100 to 0. From the data of later experiments and from knowledge of similar behavior in aquatic arthropods, a ratio of 80 to 20 is extreme. On this basis the present orientation is good. 3

If the bees are orienting by a direct analysis of the plane of polarization in the incident light, the nature of the substrate should be of minor importance. Hence, the experiment was repeated on white paper, very white but not shiny. The results (Table III) show no average orientation at all to the plane of polarization. Individual bees, however, show varying degrees of positive and negative orientation. The fact that some are negative will be discussed again later. TABLE III. RESULTS USING BEES ON DULL WHITE PAPER The sample size (sum of both vectors) and percentage perpendicular to the plane of vibration of the polarized light are shown. Polaroid Polaroid Average Bee Total % I Total _1 Count to pol. Count to pol. to pol. 1 601 54 579 51 52.5 2 378 52 364 48 50.0 3 459 37 382 49 43.0 4 107 48 334 56 52.0 5 544 52 539 40 46.0 6 1227 54 1283 51 52.5 7 568 56 397 51 53.5 Avg. 50.4 49.4 49.93 It is possible, of course, that a large reflectance signal "drowns out" an analysis of polarization, and to check this the lower halves of the compound eyes of several bees were painted out. This was done carefully so that all ommatidia directed laterally or lower were covered, using a quickdrying aluminum lacquer. The results on white paper are shown in Table IV. The orientation is in no sense restored. Although both bees were negative they are not significantly different from the seven bees of Table III. TABLE IV. SAME AS TABLE III, EXCEPT THAT THE LOWER HALVES OF THE COMPOUND EYES ARE PAINTED OVER SO THAT THE BEES SEE PRIMARILY UPWARD Polaroid - Polaroid.|I Average Bee Total % 1_ Total % I I_ Count to pol. Count to pol. __ to pol. 1 414 47 483 48 47.5 2 312 49 605 47 48.0 Avg. 48,0o 47.5 47.75

The next logical step, and one that had been anticipated before starting the experiments, was to place bees with the lower halves of the eyes painted on dull black paper. As shown in Table V, the bees showed no orientation. One of the bees (number 2) turned upside down and anticipated the next experiment, since it oriented (56*) in this position, although it did not when right side upo TABLE V. LIKE TABLE IV, EXCEPT THAT THE BEES ARE ON DULL The bees see primarily upward. BLACK PAPER Polaroid f Polaroid 1' Average Bee Total % _ Total *o l _ Count to polo Count to pol4 to polo 1 374 49 330 54 51.5 2 397 52 391 47 49.5 3 654 49 483 50 49o5 Avg. 50.0 50.3 50.15 2 (upside down) 146 56 146 56 56 0 When the upper halves of the eyes were blinded (Table VI) the bees orient a little more than half as well as normal bees. Such bees have an obvious behavioral disturbance and turn more frequently than normal bees, so that these records are about as good.- as could be expected. TABLE VI. BEES WITH THE UPPER HALVES OF THE EYES PAINTED OUT, ON DULL BLACK PAPER Data same as in Tables III-V. Polaroid - Polaroid i|| Average Bee Total % _ Total % J_ _ Count to pol Count to po Coto pol ol 1 281 67 82 54 60.5 2 215 59 718 54 56.5 3 307 60 360 57 58.5 4 321 57 307 54 55.5 Avg. 60.75 54.75 57 75 ~~~........~.......,..... 5

The implication of the two eye-painting experiments is that the observed orientation of normal bees is due entirely to cues received, from below, and not directly from the incident light. The reflectance of the substrate was examined (Fig. 1) using a photocell collimated to receive a solid angle of about 3~ (the same as is supposed for the bee ommatidium) and aimed at the paper along various sighting angles. The paper showed a slight structural grain, and one set of sightings was taken parallel to the grain, the other at right angles (front-rear and leftright in the original setup). The grain in the paper produces a small bias, so that without a polaroid more light is reflected left-right than frontrear. The effect of this paper bias appears to be added to the effect of a polaroid, for the brightness disparity between the two axes is greater with the polaroid parallel to the grain than at right angles to it (compare right and left figures). In all three cases the bees tend to run in the axis of greater intensity of reflected light, and this orientation was best for the setup producing the right-hand graph. Some of this paper was sprayed with a clear, liquid plastic that dried to form a light gloss. As a result, the high angle reflectance (Fig. 2) was increased and the low angle reflectance decreased, but the latter were more selected than before. The bias increased considerably, so that when it is opposed to the effect of the polaroid (center graph) the brightness bias is about the same (although in the opposite axis) as that of the paper without a polaroid. The bias becomes very large when the two effects coincide (right). The performance of bees on this surface is shown in Table VII. The degree of orientation is about the same without a polaroid and with the polaroid opposed to the grain (compare left and right columns), and is much greater when the two effects are added (center columns). TABLE VII. NORMAL BEES ON BLACK PAPER SPRAYED WITH PLASTIC TO INCREASE REFLECTION BIAS Data shown are the total counts and the percentage in each of the two vectors for each bee. No Polaroid Polaroid ~ Polaroid!i Bee Total Total Total Count '; Count I — Count \.. 1 587 46 - 54 723 36 - 64 600 62 - 38 2 458 41 - 59 611 27 - 73 409 54 - 46 3 141 44 - 56 237 29 - 71 167 60 - 40 4 269 47 - 53 241 48 - 52 127 46 - 54 Avg. 43.7 - 56.3 30.7 - 69.3 58.7 - 41. Omitting 4 6

50 4o 0 cd r30 F-1 — i H 0 -P Ico 20 10 Reflectance to left and right -- - Reflectance to front and rear K - 10 10 6. 8 0- 0. -- G..V.O- 0 D-01.4 4 de-:AS OP0 00ola e Plane of Vibration Front and Rear Effect congruent with paper bias No Polaroid Showing bias due to slight grain in paper 2 h Plane of Vibration Left and Right Effect opposed to paper bias 2 0 20 40 60 80 20 40 60 80 20 40 60 80 Angle from horizontal to the line of sight of the photocell Fig. 1. Reflectance patterns from dull black paper in photometer units at various angles with the paper surface. The light source is a slightly divergent beam perpendicular to the paper. In the middle and right figures a polaroid is inserted close to the light source.

5o0 Reflectance to left and right - - - Reflectance to front and rear - 10 10 (U o -a () -1, a) H 0 (D) 4 -H 4o0 8 3o 6[.,' / Plane of Vibration Plane of Vibration Left and Right 8F 6 i/ / 20 41 - /.l o - V o Fro o~' Plane of Vibration Front and Rear Co No Polaroid 2 10 2 Showing bias due to grain in paper Effect opposed to paper bias Effect congruent with paper bias 0 20 40 60 80 20 40 60 80 Angle from horizontal to the line of sight of the 20 photocell 40 60 80 Fig. 2. Reflectance patterns from dull black paper sprayed with clear plastic. Photometer units are comparable with those of Fig. 1, and show an increased reflectance at high angles but a decreased reflectance at low angles. The paper bias is increased.

In this experiment one bee (number 4) was found whose behavior was insensitive to the setup and did not vary. This is the only such bee that has been found, and it is not included in later summaries. Since the brightness pattern of the reflectance is obviously important, a method for estimating the bias was devised (Table VIII). For each sighting angle between 10~ and 400, the reflectance in the major axis was expressed as a percentage of the sum for both axes, and the average of these four percentages found. This is taken as an index of the reflectance bias. TABLE VIIIo PERCENTAGE OF REFLECTANCE IN TEE MAJOR DIRECTION AT VARIOUS ANGLES OF ELEVATION FOR THE PHOTOCELL, USING VARIOUS SURFACES No Polaroid Polaroid - Bias. Polaroid + Bias Pol. on Angle Dull Sprayed Dull Sprayed Dull Sprayed Dull Black Black Black Black Black Black White 10~ 53.2 59.7 62.6 64.3 69.2 80.1 52.0 20~ 52.1 603. 61.4 59.4 67.5 74.7 50.8 30~ 51.0 57.1 60.0 55-3 65.6 69.7 49.8 40~ 51.5 54.6 58.7 55..2 63.7 63.6 50.1 Avgo 52.0 57.9 60.9 58.6 66.5 72.3 50.5 ~~~.,........,,, When the bias is compared with bee orientation (Table IX), it that the two are closely related nd that reflectance bias becomes quate explanation for the observed orientation. is evident an ade TABLE IX. COMPARISON OF REFLECTANCE BIAS (FROM TABLE VIII) AND BEE ORIENTATION Surface. Reflectance Bees White paper plus polaroid 50.5 49.9 Dull black paper, no polaroid 52.0 51.4 Sprayed black paper, no polaroid 57.9 56,3 Sprayed black, polaroid opposed to paper bias 58.6 58.7 Dull black, polaroid opposed to paper bias 60.9 61.4 Dull black, polaroid and paper bias together 66.5 66.0 Sprayed black, polaroid and paper bias together 72.3 69.3 Polarization itself, however, has not necessarily been ruled out. Light from dark paper is polarized after reflection whether it was before or not, and it remains possible that this light must be polarized for a proper response. A variety of different experiments were designed as critical tests of this point and as further checks on a direct analysis of incident light. 9

A mirror (Table X) offers an interesting substrate, for the reflection is bright and. strongly polarized in the original plane, but has little brightness bias. Bees orient about 30% as well on the mirror as they do on dull black paper, although the polarization signal is doubled. This is a critical experiment that should be repeated on other organisms. TABLE X. RESULTS WITH BEES ON A CLEAN MIRROR SURFACE WITH EXTRANEOUS REFLECTIONS REDUCED AS FAR AS POSSIBLE, AND CONTROL EXPERIMENTS WITH THE SAME BEES ON DULL BLACK PAPER Data shown are total counts and the percentages perpendicular to the plane of vjbration of the light. Mirror Paper Ratio of Bee Polar. |la Avg. Polar. Plara. |t Avg, Mir,..-0o No. %o Noo % No.. No., % % Pap. -50 1 428 52 525 51 51.5 433 70 433 61 65.5 0.097 2 690 55 597 51 53.0 372 65 543 58 61.5 0.260 3 486 56 446 51 5535 384 66 384 59 62.5 0280 4 311 56 258 54 55.0 417 59 372 56 57-5 0Q.667 Avg. 535 5 61.2 0.295 A "quarter-wave plate" (Table XI) was also used. When "Scotch Tape" is mounted at 45~ to the plane of polarization, the plane polarized light is broken into various elliptical patterns dependent on the wavelength. (For red light the ellipse is long and narrow with a long axis at 90~ to the former plane of polarization; for green light the ellipse is circular; for blue light the ellipse is broad with a long axis the same as the former plane of polarization.) The over-all effect is a weak.polarization at 90~ to the original plane of polarization. When the entire chamber is covered with tape ("general plate" in Table XI) the orientation of the bees is reversed (left) or much reduced (right). In the latter case the new weak polarization fails to overcome the paper bias. In both cases, however, the vector perpendicular to the original polaroid is reduced about 20 percentiles by the tape. In the critical experiment a 1-inch square of tape was mounted on the end of a fine wire and held over the bee at 450 to the plane of polarization. Although it is difficult to keep the tape centered exactly over the bee, its head was never allowed to be uncovered. On the average the light affected was not only all of that directly incident on the bee but also that reflecting from the substrate out to sighting angles of about 40~. It is evident from Table XI ("local plate") that this treatment had astonishingly little effect, considering the possible disturbances involved. Thus, directly incident light 10

and high-angle reflections are both ruled out as significant factors in this behavior. This is another critical experiment that should be repeated on other organisms. TABLE XI. EXPERIMENTS WITH A QUARTER WAVE PLATE OVER SPRAYED BLACK PAPER One bee, -Actual counts in both vectors are shown, together with totals and percentages at the bottoms The "local plate" is a 1 -inch square held. over the bee as it moved; the "general plate" is a 12-inch square covering the entire chamber.;_____ Polaroid.- ___ Polaroid._ Trial' No Plate Local Plate General P1. No Plate' Local Plate General P1. 132 - 72 107 - 57 69 - 102 46 - 124 53 - 137 85 - 108 2 1 129 - 67 102 - 65 5 6 - 91 46 - 15 48 - 120 96 - 114 3 129- 64 53 -3 5 58.- 75 -415 - 55- 63 4 70 - 55 34 - 98 74 - 98 5 73 - 56 44 - 125 64 - 76 6.69 - 43.. ____33 - 80 __ Total 602 357 262 157 191 268 248 712 101 257 374 459 65 - 37 62 - 38 42 -58 26 - 74 28 - 72 45 - 55 Change of o _____- 1 I - 21 - 2 - 19 Two attempts were made to provide the bee with a surface so biased in its reflection that opposed polaroids are overwhelmed. In one case mirrors were mounted on opposite sides so as to reflect the overhead light onto the paper. The reflectance bias was about 88%. With the polaroid in its two positions the bias remained in the mirror axis at 91% and 70%. Bees under these conditions oriented 71%, 76%, and 66%, respectively. A smooth surface of norite-blackened beeswax was carefully brushed in one direction with a wire brush. The resulting grain had a reflectance bias of 89.7%0 without a polaroid, 92.4% and 76.8% in the same axis with a polaroid. Bees oriented to this axis at 66.35, 67o, and 61.3%, respectively. Because the reflectance of black wax is high and reflected secondarily from the glass cover, these bees had the top halves of their eyes painted out. All these data are gathered together in Fig. 3, where bee orientation is plotted against reflectance bias. Each surface is identified with a letter and is defined in Table XII. Normal bees appear to have a maximum orientation at about 75%>, while those with the upper halves of the eyes painted behave one-half to two-thirds as well. If the location of the 11

Ca 74 a) |d r1m a, o 70 0d~~~~~~~~~~~~~~~)~ ~ ~ ~ ~ ~ 62 -6- 6 surfaces / 2 'es8 - 0 to n C Slalie: lb 58 -Crsss0 2b b ee -e _ P^ - XC 50 58 62 66 70 7 78 82 86 bee90 surfaces (a to n). Solid lines: Normal bees. e 50 0 b c de f g h i j k 1 m n 50 54 58 62 66 70 74 78 82 86 90 Reflectance Bias: % major vector in sum of two vectors at 90~ Fig. 3. Relation of bee orientation to the reflectance patterns of variou surfaces (a to n). Solid lines: Normal bees. Open circles: Bees with the upper halves of compound eyes painted out. Crosses: Bees with the lower halves of compound eyes painted out. Crosses in circles: Like crosses except that bee was upside down throughout readings.,s

TABLE XIIo SUMMARY OF THE VARIOUS SURFACES USED IN FIGo 3, SHOWING THAT REFLECTANCE BRIGHTNESS BIAS ALONE EXPLAINS MOST OF THE REPONSE Surfaces without Overhead Polaroid. bb Dull black paper, slight grain bias. do Sprayed black paper, moderate grain bias. ko Sprayed black paper with side mirrors reflecting onto paper, strong bias 1o Black wax with fine parallel scratches, strong grain bias. Surfaces with Polaroid which Is Major Factor Determining Reflectance Bias: ao White paper, slight brightness bias on top of general depolarized reflection. co Clean mirror, slight brightness bias on top of bright, fully polarized reflection. e. Sprayed black paper, polaroid effect reduced by opposed grain bias. f. Dull black paper, polaroid effect reduced by opposed grain bias. go Dull black paper, polarization effect increased by congruent grain bias. i. Sprayed black paper, polarization effect increased by congruent grain bias, Surfaces with Polaroid which Is a Minor Factor Congruent with Major Factor: m. Sprayed black paper with side mirrors, effect increased by polaroid. n. Scratched black wax, grain effect increased by polaroid. Surfaces with Polaxoid which Is a Minor Factor Overruled by Major Factor: ho Sprayed black paper with side mirrors, effect reduced by opposed polaroidO jo Scratched black wax, grain effect reduced by opposed polaroid. various kinds of surfaces are studied, it becomes apparent that no class produces data following a different trend. Hence, it is concluded that bias in the brightness of the reflectance pattern contains all the information used by the bees in this behavior. Polarization itself is not analyzed. As a final experiment, a film of white paraffin was placed over the compound eyes. Such a film, about 0.2 mm thick, transmits tolerably well but almost completely depolarizes incident light. The initial results (Fig. 4, open circles) were surprising, since the orientation is clearly negative for substrates with a low reflectance bias. It was then discovered that the brightness of light transmitted through a paraffin film that is illuminated obliquely on the other side is sensitive to the plane of polarization, but opposite to the effect of reflection. That is, the transmitted light was brightest when the observer looked in the axis of the plane of polarization rather than at right angles to it. 13

54 D4_ -0237 r555 ________0 L l^^2049 H 50 1012 0 L / 22 ~ O 1101 / / 46 6 ^6 -243 k 0 (!) m 42 -each line indicates 3635 one bee c f g i Reflectance bias (same scale as Fig. 3) Fig. 4. Results with bees having a depolarizing film of white paraffin over the compound eyes. Open circles: Both eyes completely covered with paraffin. Half black circles: Upper halves of eyes painted black, lower halves covered with paraffin. To overcome this effect of the direct illumination, bees were prepared with the upper halves of the eyes painted with aluminum lacquer and the lower halves covered with paraffin. Such bees (half black circles on Fig. 4) behave about one-fourth as well as normal bees, or half as well as bees with paint but without paraffin. That bees so treated have any visual acuity left at all is surprising enough, and little support is left for a role of polarization. We would now like to show two things further: (1) that reflectance patterns with adequate bias are present in the experiments of von Frisch; and (2) that orientation to the reflectance-scatter pattern is a simpler explanation of the behavior than response to polarization directly. 14

Accordingly, we can now pass to the actual lighting conditions of von Frisch's experiments. To duplicate the geometry of his experimental conditions, we placed a brood comb in a horizontal position in front of a north window, It was illuminated by the north sky from 30 to 60~ of altitude and about 40~ of azimuth. A sheet of polaroid matching the polarization of the sky was superimposed on the comb. Since we wished to see the reflectance-scatter pattern visible to a bee's eye we took a bee's eye view of the comb by poking a peris~cope up through a small hole in the comb, The periscope was rotatable in 360~ of azimuth, and adjustable in the angle of view of the substrate. A photomultiplier looked into the periscope to measure the intensity of reflectance and scatter. The light intensity reflected and scattered for a 10~ sighting angle is plotted on polar coordinates in Figo 5. The arrows indicate the plane of polarization of the incident light on the brood comb. In general the pattern is elliptical and the long axis points at the sun. By altering the sighting angle of the periscope to 300 and repeating the measurements at every 15~ of azimuth, one obtains the reflectance scatter diagrams seen in Fig. 6. The arrows indicate the plane of polarization of the incident light. The long axes of the patterns are still discernible except-in the case of a north-south plane of polarizationo We shall say more about this pattern latero Since the bee moves about freely and sees all aspects of the comb, it is important to know whether different orientations of the comb relative to the incident light will change the appearance of the reflectance scatter patterno Figure 7 shows reflectance-scatter intensity plots of a 10~ sighting angle at the brood comb in four different positions, each rotated 90~ from the preceding. This demonstrates that the larger geometry of the brood comb has little effect on the reflectance-scatter pattern. It is also important to know the effect of other bees on the reflectancescatter pattern. This is seen in Fig. 8, where the field of view of the periscope was almost completely covered with bees. Arrows indicate the plane of vibration of the incident light. Although this is somewhat different from Fig. 5, the patterns are recognizable. It should be pointed out that the bees used here were dead and may have failed to reflect light like live bees, With certain exceptions the published data of von Frisch concern the behavior of bees with the superimposed plane of polarization at right angles to the direction of the sky used or at 10 or 200 from this position. The reflectance-scatter patterns for these positions of the polaroid are seen in Figb 9o Regarding simplicity of postulates, it is already known that bees are positively phototactic and have considerable ability to discriminate slight 15

North I Window t w N S Fig. 5. Readings cated by pattern. Reflectance patterns from a brood comb at a sighting angle of 10~0 were taken with the polaroid in four different positions as indithe arrows, showing the effect of the plane of polarization on the Averages of three readings with the comb in one position. 16

North Window t Fig. 6. Reflectance patterns from a brood comb at a sighting angle of 30~. Polaroid in four different positions, as shown by arrows. 17

North Window co 1 Fig. 7. Reflectance patterns from a brood comb at a sighting angle of 10~. Light source a piece of north sky. Polaroid sheet over brood comb with the plane of polarization east-west as shown by the arrows. The pattern was recorded with the comb in four different positions, successively rotated 90~ clockwise as shown in lower figures. The stability of the basic pattern exceeds the effect of local irregularities. Data are plotted as polar coordinates with intensity as distance from the origin.

North 4. Window t 4 Fig. 8. Like Fig. 5, except that 38 dead bees have been placed on the field of vision. In spite of greater reflectance, the basic patterns are preserved. 19

North Window 4 Fig. 9. Reflectance patterns from a brood comb at a sighting angle of 10~, showing the effect of small deviations from east-west in the position of the polaroid. Each point is an average of two readings for each of two positions. The southward points in the center and right figures represent obvious comb irregularities. 20

brightness differences. It is no great step from discrimination of brightness differences to recognition of relatively uncomplicated scatter-reflectance patterns with their long axes indicating the position of the sun. Further, it has been shown that the bee has an effective clock. If the position of the sun and the time of day are known, it is possible to indicate a compass course toward any desired object. This would appear to be a simpler explanation of the observed behavior patterns than having the bee remember the entire polarization pattern of the sky for all hours of the day for several days as is necessary for von Frisch to explain his results on cloudy days. 21

DISTRIBUTION LIST (One Copy Unless Otherwise Noted;) Office of Naval Research Biology Branch (Code 446) Washington 25, D. C. (2) Commander Naval Air Test Center Aero Medical Branch of Service Test Patuxent River, Maryland Director, Naval Research Laboratory (6) Washington 25, D. C. Attention: Technical Information Officer Office of Naval Research Branch Office Tenth Floor The John Crerar Library Building 86 East Randolph Street Chicago 1, Illinois Office of Naval Research 346 Broadway New York 13, New York Office of Naval Research 1030 East Green Street Pasadena 1, California Branch Office Branch Office U. S. Navy Office of Naval Research Branch Office, Box 59 Navy No. 100 Fleet Post Office New York, New York Director, Office of Sciences Office of the Assistant Secretary of Defense Research and Engineering Department of Defense Washington 25, D. C. Office of Technical Services Department of Commerce Washington 25, D. C. Director Marine Biological Laboratory Woods Hole, Massachusetts Director U.S. Navy Underwater Sound Laboratory Fort Trumbull New London, Connecticut Commanding Officer U.S. Naval Ordnance Test Station China Lake, California Chief of Naval Research Department of the Navy Washington 25, D. C. Attn: Code 454 Research and Development Division Department of the Army Office of the Chief Signal Officer Washington 25, D. C. Commander, Air Force Office of Scientific Research Washington 25, D. C. Attn: Director Biological Sciences Division Executive Secretary Armed Forces Pest Control Board Forest Glen Section Walter Reed Army Medical Center Washington 12, D. C. Director Scripps Institution of Oceanography University of California La Jolla, California Attn: Drs. E. and B. Boden 23

DISTRIBUTION LIST (Concluded) Director Bermuda Biological Station St. George's West Bermuda, British West Indies Executive Director Division of Biology and Agriculture National Research Council 2101 Constitution Avenue, N. W. Washington 25;, D. C. Dr. Lionel Jaffe Department of Biology Brandeis University Waltham 54, Massachusetts Dr. John Co Lilly Communications Research Institute Sto Thomas U. So Virgin Islands Dr. P. W. Gilbert Department of Zoology Cornell University Ithaca, New York American Institute of Biological Sciences Advisory Committee on Biology (8) 2000 P. Street N. W. Washington 6, Do C. Dr. Donald R. Griffin The Biological Laboratories Harvard University 16 Divinity Avenue Cambridge 38, Massachusetts Dr. F. H. Johnson Biology Department Princeton University Princeton, New Jersey Dr. Donald So Farner Department of Zoology State College of Washington Pullman, Washington Armed Services Technical Information Agency (10) Arlington Hall Station Arlington 12, Virginia Dr. Vincent G. Dethier Department of Zoology University of Pennsylvania Philadephia 4, Pennsylvania Dr. Otto H. Schmitt Department of Physics University of Minnesota Minneapolis, Minnesota Dro A. Do Hasler Department of Zoology University of Wisconsin Madison 5, Wisconsin Dr. Talbot H. Waterman Osborn Zoological Laboratory Yale University New HaVen, Connecticut Dr Howard A. Baldwin Applied Research Laboratory College of Engineering University of Arizona Tucson, Arizona

UNIVERSITY OF MICHIGAN 3 9015 02223 2170 3 9015 02223 2170