FORMICA Yessensis Foreli) ' (FORMICA) Iselgo Higashi, Zbolagical Institute, F21culty of Sle:Ience

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Htspmvkts (Jap. J. EcoL), 28:307-317, 1978

TASK AND AREAL CONSERVATISM AND IN[[ERNEST DRIFI[NG ' IN A RED WOOD ANT FORMICA YEssENSIS FORELi) ' (FORMICA) iSelgo HIGAsHI, Zbolagical institute, F21culty of Sle:ience. Hbkkaidb Uhiver:sity, Smporo 060

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HiGAsHl, Seigo (Fac. Sci., Hokkaido Univ. Sapporo), 1978. Task and area1 conservatism and internest drifting in a red wood aiit R)rmica (Fbrmiea) yessensis FoREL. Jap. J. Ecol., 28 : 307-317. formi'ca (l7brmica) yessensis FbREL has a supercoIonial system. Each worker ean visit any con- specific nests without receiving hostiHty. Although this systern suggests irregular roaming of workers in the field, the present study clarifies that many, ifnot al1, workers are fairly conservative to panicular tasks or working areas for a certain peried.

all made at Ishikari Shore, Hokkaido, Japan. As a introduction part of this serial study, the present paper deals Some ant species of Fbrmica rLij2i-giroup, to which with task and areal conservatism as well as inter- E yessensis belongs, have been studied extensively nest drifting, mainly based upan the observations

in Europe in connection with their application to of individually marked wotkers. forest protection for the foIIowing reasons: 1. Many students have repdrted en worker poly- Nests can be artificially translocated. 2. Absence of ethism in ants (OKLAND, 1931, GOTscH, 1933, KirL, internest hostility due to polydomous system en- 1934, DoBRzANsKA, 195,8, 1959, OTTo, 1958,

ables free internest visits among workers. 3. High WALtis, 1964, HoRsuaNN, 1972, 1973, etc.).

nest density can be maintained if some conditions, Studying several species'of Fbrmica and other e.g. abundant food or adequate sunlight, are satis- genera under both field tind laboratory conditions,

Nest is large the maximum DoBRzANsKA 1959) clarified the attachment fied.4. population (in (1958, 'working to tasks areFs some 5 × 105 to 1 × 106 in E polyctena FORsTER and particular qnd in 1× 105 in F: rtofli L., G6sswALD, l951; 8× 103 to workers. In E yessensis, it was suggested that 1 × 104 in E truncorttm FABRicius, Sf[Tz, 1939; starting from intranest tasks larger workers' change 5.1 × 104 in E yessertsis., ITo, 1973>. 5. Workers are to hunters while Smaller ones to aphid milkers edicient hufiters of various insect pests, both adults during their life span, which is shorter than bne and iarvae. 6. Nearly innoxious exoept for pro- year in most workers (80%) (HiGAsHi, 1974, 1976). tection of aphid fbr milking. ln Japan no study has But individual partiality in polyethism has not been boen made with E yessensis from su ¢ h practical confirmed under field conditions before the present point ofview. Our research group has studied vari- study. ous aspects of the biology and the ecology ef this Before going further I wish to express my sinoere polydomous species, e.g. nest distribution (ITo, gratitude to Dr. Sh6ichi F. SAKAGAMi for his peni- 1971), seasonal population trends and nest struc- nent guidance through the pfesent study. tures (ITo, 1973), hibernation (IMAMuRA, 1974), Methods an{l Results nuptial fiight and internest relationship (ITo & IMAMuRA, 1974), worker polyethism (HiGAsHi, From June 30 to July 3, 1973, 412 workers were l974), and growth pattern of nests (HiGAsHl, 1976), captured on nest A and individually marked in with using combi- Accepted Apr. 12, 1978 laboratory quick-dryingdyes and 1) Biological and Ecological Studies of a Supercelonial nations of four colors (red,yellow, green ant fibrmiea ptessensis FoREL VII. purple). After the rnarks applied to gaster, thorax 307

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and legs had dried, the ants were released on A on formanoe around A were fo11owed once to '5 thrice July 4. From July to 21 their presence and per- per day, in total 21 times, spending two to eight hours to complete a tour around the nest. Once a Wlthered grasses va ot twigt marked worker had been found, her distance arid as Sond direction from A and her performed task were ' recorded. When the same worker was found again Msinensis g during the same tour, the record was taken only if ntemctell rmft. she was more than 1 m distant from the first place or was engaged in a task different from that in the

first detection. On July 8, 34 additional workers caught at milking aphids were marked and released

on A. They were traced from July 9 to 21, in total

13 times, together with the workers released on July 4. NAO2 Nest A was in zone C in Ishikari Shore (cfi ITo, v ts/ 1 971); where grasses were so sparse that finding and tracing of marked workers were relatively easy. Ul Nest density was relatively lower around nest A than in other parts of zone C. The part east of A axlelxttomIl' was covered with Etluisentum hiemale (Fig. 1), making the detection of the marked workers diM- 8 cult. Some crowds of MTscanthus sinensis oocurred vtQ in.the western and eastern parts visited by many aphid milkers. In other parts grass density was very sparse. Excluding A there were nine nests within a - 7m- radius of 7 m froM A, and these and ttu:ee other Fig. 1. 0bservation area in July, 1973. nests near the area we.re patted at each tour in order A: SurfaQe of 4est A. Srnall alphabetical letters to lure oui marked workers having drifted in them. hain show'Topographygntrances. The same census was repeated in mid September B: of the area within 7 m frorn nest because of A. .Roman numerals show nests. when worker activity became sluggish the cold. On another nest B about 1.5 km distant skeensts eAbandoned nest gsc from A 103' workers were caught and individually marked in the laboratory on September 13 and 14. They were released on B on September 15 and traced twice or thrice per day frorn 16 to 21, in total 1 1 times. B was also in zone C as A but was almost isolated frorn other inhabited nests, Only two un- inhabited nests occurred within a radius of 7 m around B (Fig. 2). The two nesits were probably abandohed by emigration of inhabitants to other hibernation hests (HiGAsm, 1976). The grass density was extremely low except fbr some crowds of A4: slnensls. Fig 3 shows the relationship between rediscovery frequency and number of workers. Among 412 ･4 workers relea$ed on July 139. were never rediscovered and 58 only onoe. The number of workers rediscovered twice or more showed an unimodal distribution with a peak of 48 workers rediscovered

four tlmos. The number of workers rediscovered i times, i.e. Fig. 2. Topography of the area within 7 m from nest B at n censuses is expected to be by the observed in September, S973. F(i), given 308

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following formula, provided the chance of rediscovery was nearly equal in all tours and most rnarked workers stayed inside the inspected area: F(i)=:N･nCi･Pi-(1-P)n-i ' in which IY is total number of marked workers and P the mean of chances (P) by which each worker is rediscovered at each census.

As mentioned later, each worker, on ¢ e fixed to particular working area, does not quickly disperse SgetnE=z to other areas, rather tending to stay in her own area. This habit should increase the probability of

rediscoyery for each worker. In the present obser- Ol234S67e9 ro ll 12 IS vation, however, rnany workers were never or only onoe rediscovered. Some of them might have died becauSe of the marking, others were probably lost by drifting away in the earlier stage of the observation period before they were fixed to a particular working area. Actually, about 62 % (36158) of only

onoe rediscovered workers were observed during Rtdtscorvery f;equencr the first three days. Fig. 3. Relationship between [ediscovery frequency Excluding them, the maximum F(i) was obtained and number of workers, at = = 21). Therefore, and N are estimated i 4 (n P The dotted line in A connects the yalues calculated as about O.2 and 220 respectively, because, to have by the formula: the maximum of F(i) at i = 4, P must be within the F(i);220･2iCi･O.2t･O.82t-tl2-2iCi･(lf4)i range which satisfies the fo11owing two conditions at the same time: lated number (220). b) During this observatiog marked wotkers were rediscovered 1,060 times in 2iCB-P3･(1-P)i8<2iQ･P4･(1-P)i7 ...... (1) total, and the mean number of rediscoyered 2iC,･P5･(1-P)16<2iC,･ju-(1-P)i7 ...... <2) workers per one tour was 50 (1,060/21). Thus, From 1) and 2) P is calculated as O.18

were lost from the inspected area in the early period.1. period, the total number of workers staying in the Tftsk and areal censervatism area was 231 (412-181), being close to the calcu- Most frequently rediscovered workers showed a

3e9

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28, VoL No. 4 H 7ts ts re \ ft ts Dec. 1978

Table 1. Representative individual records in July, 1973, showing typical (Nos. 120) or exceptlonal (Nos. 21-24, 31-34) working patterns or workers traoed in late July to early August (Nos. 25-30). Bi: Intranida} building (small alphabets == entrances of nest A, cf. Fig. 1). Be: Extranidal building. Wo: Wandering on A. Wi: Wandering within 1.5 m from A. W2: Ditto, 1,5 m or more from A, Ap: Aphid milking. D: Digging in the field. P: Prey carrying. Distance and direction from A are also added to, e.g. Ap4NE == milking aphids at 4 m north-east from A. 6roup A: Workers mainly building nest. B: Workers mostly milking aphids. C: Workers mostly wande[ing. ln Nos. 14-24, distanoe from the point of first discovery is also shown. D : Workers traced from July 23 to August 9. E: Workers participating in two tasks or more.

Group and Date (al1July) of census and in parenthesis hours spent for each teur individual 5a 5b 5c 6a 6b(s)15(8)7a(s)16(8)7b 8 9a(s)20(8)9b(4)21(8)10(6) number (3) (2) (2) (4) (5) (S) 11 12 13 14 11 18 1 ･(8) (5) (8) (8) (8) (8)

1 Bi-a Bi-a Bi-a Bi-a Bi-a Bi-a Bi-a Bi-a Bi-a Bi-a - Bi-a ek'?3w------t A2 - Bi-d - - Bi-d Bi-d Bi-d Bi-e - Bi-e Bi-e rm - m - m - - - - - / No. 3: Bi-a(5b, 5c, 6a, 7a), Wo(13). No. 4: Wo(Sb), Bi-c(7a), Bc & Bi-c(8), Be(9b, 12), IV(17). No. 5: Be(6b, 8, 12, 13), Wi (17). 6-

Ap3.5 Ap3.5 Ap3.5WNW"wPkw5- , WSW WSW Qtt5- B7 Wl Ap4 WNW Ap3.5WNW".pGw5 Gp.3w5 Qp.3w5 - i No. 8: Wo(7a), Wi(8), W2 3.5N(12), Ap4NNW(13, 16, 17). No. 9: Wi(8>. W22.SN(12), Ap4NNW

(13, 16, 17). No. 10:W2 2.5N(8), Wi(9b), W2 3.SN(12), Ap4NNW(IS), Ap3N(16, 17 ,18), No. 11: Wo(11), W2 2.5wnW(13), Ap3.5WNW(14, 15, 16, 17, 18, 21).

12 Wo WlWl Wo Wo Be Wt Wl Wl13 Wl WlWl fWo Dl.SNNE Dl.5NNE Wl WlWlW22.5NNE(o)WlWl Wl14 f W22.5NNE(o) VV23.5NNE(1)WoW22NNE(O.5)W23NE(la2)W23NNE(O.5)W23NE(1,2)W24.5NNE(2.0)

W23NW(o)W23WNW(1.1) W23NW(o) W23NWW(1.1) Wl

C 15 W22,5 - - - W / (2,2)

No. 16: Wi 10), Wz5NNE-O(7a), W22.5NNE=2.5(9a) (6a, ,W22.5NE-2.9(13),P3.5W=1,5(18). No.17: W22.5SSW--orSc), Wi (9b, 11), W23.5SW==l.al2), W22.5SSW-or16),W23SSW=O,5(17), W22,5SSW-O(18). 18: W22.5NNE-O(7al, W23N==1.2(7b), Ne. W23.sN=1,6(10), W23N=1.2(14) ' W22.5N=1.0(18), W23.5N=1.6(21). No. 19: Wi (6a, 9a), W22.5SSW==or11), W22.5S-1,or12), W22,5SSW=O(le,W23SSW==O.5(17),W23S==1.2(18).No.20:W24WNW==O(9a),W22.5WNW=-1.5 (ll), W23.5WNW-O.5(12), W23WNW-1,O(13), W22.5WNW-1.5(15), W23.5WSW!O,5(17).

conservatism as to tasks or working areas both 1.1 Conservatism in nest,building (Table 1 A) individually fixed for some days. Some workers were found throughout the observation only when carrying out sand grains from

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Table 1. (Cbntinued)5irv 5b(2)12(8)5c(2)13(8)6a(4)14(8)6b(5)15(8)7a(5)l6(8)7b(5)ll(8)8(5)1'8(8)'9a(5)20(8)9b(4)21(8)10(6) (3)11(5) t W23N 21 - - - - - (o) W22.5 W24 W24 C m rm m WNW WSW - - - WNW /W2 (3.1) (5.9) (4.0) No.22:2.5S-or9a),W23WNW=-or10), W23W-1.1(11), W24WNW-1.0(12), W22.5NNE-3.9 No.23: W22.5WNW=:4.2(16). No.24: W22,SW=!O(11), W25NNE-6.4(21).

No.2S : Wi(8), W23WNW(10), P5N(l1), W24N(14), W23N(11), W24N(21). No.26 : Wo(5b), Wi(9a),

W22.5S(11), W23S(12), W22.5S(17), Wu2S(18), W22,SSSE(21). No,27: Wo(8), Wi(9a, 10). D W22.5SSW(11), W22.5SSW(12), W22S(13), W24SW(l6). No.28: Wi(5al, Be(5b), Wo, 3,5NW(12),

W23.5N(IS), No.29:Wi(7b, 9a, 12, 20), W22,'5NW(11), W22.5NNW(l6). No.30: Wo(7a), Wi(7b,

9a, We3N(13).

- W22.5 31 WNW W23WNW Ap3.5WNW Bi Ap3.5WNW- - !

W22,5 W23 be Wl Bi Wo - 32W23W WNW WNW Wz2.SWNW Ap4WNW ' 1 E Wl,23.5NW-

33 Ap4NWAp4 in Ap4NWplNNWAp3NAp4NW W23 P3.5WNW NW WNW t 34 IYev2･5 wo,i Ap3N Ap3N W22.5N wo - 1

nest A, each tending to pass through a fixed nest 12.and l3 but another stock at 3.5 WNW from entrance for seme days: No. 1 carried eut sand July 16 to 20. Even when a worker visited two or grains only at entranee a (Fig. 1 A) from July 5 to more stoeks, thesc stocks stood near by. As a 12 until found wandering at 3 WNW (3 m WNW whole, 20 workers in July and 7 in September were of A) on July l3. No, 3 used only entrance a from at milking twice or･more. Each of 17 out of 20

July 5 to 7. No. 2 used only entrarioe d from July workers in July visited the stocks less than 1 m

5 to 7 but e from' July 8 to 10. No. 5 arranged the distant from the stock of their fust discovery nest .mound from July 6 to 13 unti･l she wandered (Table 3 A). The maximum distanoe between two near the nest on July 17. ND. 4 arranged the nest stocks visited by a same worker was 3.2 m. All

mound on July 8, 9 and 12 but carried out sand observed aphid milkers in September were found grains on July 7 and 8, and was found on nest IV on on the same stock (Table3 B). July 17. In the observation in September, no mark- 1.3. Wandering out of the nest (Table 1 C and 2 B) ed worker was engaged in nest building at nest B, Many worke!s waridered eut of the nest, most of though some unmarked ones engaged in building. them probably searching food or nest materials but 1.2. Aphid millting (Table 1 B and Table 2 A) some others on the way to the stocks harboring Sorne workers were constantly observed at milk- aphids, or aiming at other nests in search of trans-

ing･aphids on a fued stock of M. sinensis for certain portees or returning home nests. in days both July (Nos. 6-1 1) and September (Nos. 1.3.1. Wandering e" or near the nest 35-41). No, 40 was found eight times only milking Some workers spent most of their time on

on a fixed stock at 2.5 N of B from September 16 to or near the nest. No. 12 wandered always on or 20. No. 6 visited a stock at 3.5 WSW of A on July311 near A throughout the observation in July, not

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Table 2. Representatlve individual records in September, 1973. 0bservation hour: a, 6;30-9 :oo; b. 11:OO-14:oo; c, 15:OO-17:oo. A: Workers mainly milking aphids (No, 35 milking aphids on M. sinensis by the nost). B: Workers mainly wandering. Other symbols as in Table 1.

Greup and Date of census (September) indMdual 16 17 number a b c a c a18c a19c a20c

35 -36･ ApAplEE ApAplEAplEAp2.5N Ap ApAplEAplEEAp2,5NApl.5SSEAp2.5NWIApAplE AplE AplEAplE AplEAp1EAp2.SNApl.5SSEAp2.SNAplE - AplEAp2.5NApl.5SSEAp2.5NAp3Ss 37 aPl Ap2.5NApl.5SSEAp2.5NAp3s Ap2.5NApl.5SSEAp2,5NWtAp2.5NApl.5SSEAp2.5N A 38 - Apl.5SSE 39 ri Ap2.5NW23s Ap2,5N 40 - W22S Ap3s 41 IY22.s

42 -43 Wl Wl - Wl WtWl Wl W23NE - Wiag WlWlWl Wl WlWlW22W Wz2SSEWI W22.5ESE - WlWlWlP WlWlW2ZEWl,22WNWW22WNWW22WNW Wa2W B 45 VVi46 Wl W22.5ESEW22 Wl47 Wl WlWiW22W

- W22w W22.5 W22.5 - WtW22.5NWW21,5WNW1.5S WNW WNW W W22W - W22.5WNW 48 - W22W WE2.5W 49 W22.5 W22WNW W22.5WNWW22WNW - W22W NW

participating in any tasks except when she arranged in July and 24 (96%) in September were always the nest mound on July 8. Nos. 13 and 42 also found each within 4 m from the point of their first frequently wandered on or near A and B respective- discovery Crable 3 C, D). Wandering areas in ly.1.3.2. September were on the average smaller than in Workers having a wandering area in the July. field. Six workers (Nos. 2tP30) were traced for two to Most workers were found wandering in the field four hours in late July to early August in order to 1,5 m or more awqy from nest A or B but their see whether they wander within a limited area or wandering areas were rather limited. For instance, not (Fig. 4). In these observations, only the range No. 14 was first found at 2,5 NNE on July 6, and of wandering was recorded by' plotting the points at the later seven times of observation was still in each directien most distant from the peints of Within 2 m from the point of the first discoyery. first discovery. Among these workers, No. 25 was No. 19 wandered in the ak:ea within 1.2 m from traced thrice, No. 27 twice and others once. No. 25 2.5 SSW the point of her fust discoyery. No. 24 was always fbund 3-5 m north of A in tours on July was found, however, at 2.5 W on July 11 but at 5 to 21. Later she was traoed two hours on July 23,

on August 9. 5 NNE on July 21, these two points being 6.5 m fourhours on July27 and two hours apart, Nos. 21-23 were also found at widely sepa- The first two wandering areas completely over- ratec! points. As a whole, each of 103 workers in lapped, but the third area was quite distant from July and 25 in September was found twice or more the two previous ones. In No. 27 two areas nearly wandering at points 1.S m or more apart from A overlapped each other. The maximum diameter of and B respectively. Out of these, 96 workers (93 %)312 these areas were: 3,60 m (No. 25, July 27, 4 hrs.;

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Tab]e 3. Number of workers grouped by their maximum dispersal distance from the point of first discovery, with frequency of rediscovery. A, B: Aphid mi[king in July and September respectiyely. C, D: Wandering in the area 1.S m or more destant from A (July) or B (September) respectively. T: Total. W % : Weighted %.

Maximum distance Frequency of rediscovery from the point of % W% first discovery 2 345678910T

Om<1<2<3<471o11105oooo5 1o1oo211ooo21oooo1oooooooooooooooooooooooo15211120 75 75 10 85 Ao<1$2-S3S 5 90 s 951oo s1oo T x Bo o1o1122oo 71ooloo

o$152$3$4S5S6S<1<2<3<4<5<6<7628512o143o16621oo25o64411o16o92o1oo12o41oooo5oooooooooo11ooo2oooooooooooooooo 6 6 667 63 61 19 18 859398991oo c 8 8 5 5 1 1 1103 11oo T 1

05 <1<2<3<4<574oIo12232o1812ooo31ooooloooooooooooooooooooo'ooooooo1o1 11922l2Sop `t`f ISD 36 80 2S 8 gs961oo 3S 8 4S 41oo T 1

No. 25, Aug. 9, 2 hrs.), 3.30 m 27, July 25, 'No25 ""'"'No.30 (No. ------Npt29 "--- Ni2T No.26---No28 2 hrs.), 2.90 m (No. 28, July 28, 4 hrs.), 2.60 m (No. 27, July 29, 2 hrs. 42 mins.X 2.40 m (No. 30, Aug. 8, 4 hrs.), 2.36 m 25, July 23, 2 hrs.), (No. 9 2.30 m (No. 26, July 24, 2 hrs.), 2.20 m (No. 29. t<,, Aug. 5, 2 hrs.). lcc More precise tracing of wandering courses was tried with some workers in May, 1975, as foIIows : 3 1 1) An area of 1O × 10 m square was chosen and 441 N.-S (21× 21) short poles bearing recognition marks were put, each being 50 cm distant from neighbor- a n ing poles. The poles were plotted on section papers. Fig. 4. Wandering areas of six workers (Nos, 25-30) 2) 50 workers were individually marked on a nest traced from July 23 to Aug, 9, in the center of the area and their courses were

traced on section papers. Only two workers (Wl adult worker into the nest but mainly wandered in and W2) wandering in the area of sparse grasses search ofyoung buds of Rosa rngosa to gather saps, could be traced sucoessfuIly for over an hour, with- W2: Traced from 11:03 to 12:28, May 28 (Fig, out being lost (Figs. 5 and 6): 6). The wandering area was oval with its IQngest and Wl: Traced from 10:58 to l3:52, May 7, in- shortest axes 1.9 m and O.8 m respectively. She did cluding a stay in the home nest (12:16 to 12:39). at least four tasks, carrying a prey, digging in the She was out of the nest for about 145 minutes, field, carrying nest.material, gathering saps from staying about one half of the time in an area of young buds of R. rtrgeSa. 1.5 m in diameter (Fig. 5). Once she transported an

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10 3nO)11 1 1 f n'un. E g Tra"spert of worker rw Wanderlng ee Stroight wqlking MOn the grass stock -Gatherlng sop ef R. rugosa Z Restlng ct nest entrance pm out of sioM n=ln the nest Fig. S. Continuous record of a worker Wl (10:S8-13:S2, May 7, 1975). Numerals in the course correspond to those in the temporal sequence, given below. Dotted circle shows the area where she stayed about

half of her foraging time.

w u a 7 was also observed on May 9 (11 :45, 15:35) and 12 (9 :40, 12 :oo) suggesting her partiality to this task at least for five days. Nest 1.5. Workers participatirrg in two tasks or more CTable 1 E). ll:03 2e 3o 4o so 12:oo 10 20 2S During the observation in July, 14 workers car- w t E P.caTlog-ofptny Dtorgging MiCkaas::il ried out each two tasks or rnore, intranidal building ge ef nest (Bi), extranidal building (Be), digging in･ the field Fig.6. Continuous record Qf a worker W2 (11:03- aphid milking and caniage of 12:28, May 28, l975), (D), (Ap) prey (P), that the Explanations as in Fig. 5. suggesting partialitytoa certain task isnot absolute: Bi and Be (one worker), Bi and D (1), Bi and Ap Bi and P 1.4 Transporting adult workers (4), (2),Be and Ap (3),Be and ･of P(1), Ap and P Bi, Be No worker clung to transport celony mates (2), and Ap (1).Forinstance, carried sand out nest on through the observations in 1973, but one instance NQ.,31 grains from A July 12 but was milking 13 18. was observed in May, 1975: On May 8 a marked aphids on July and No. was worker (W3) repeated adult transport from a small: 32 observed at extranidal buitding(July5), intranidal er nest to a larger nest 75 cm distant. She carried building(July7) and milking aphids carried a after adults into one same entrance of the large nest at a (July18).No, 33 prey two hours milking aphids 11), though later she yisited pace of two adults per ten minutes. Sorne non- (July aphids seyeral times, no marked marked workers participated in adult transport to- In September,

gether .with W3, carrying 23 transportees in total workers doing any task other than aphid miiking were found. for ten minutes, and this suggests participation of about 11 or 12 workers (2312) in this task. Trans- 2. Drifting into other nests (Table 4) port by the matked worker between the same nests In July, 39 out of 446 workers were rediscovered

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on other nests around A when these nests were that1egll patted at each tour, some on the nests near A, e.g. :.E N 1 1tuzt is:.ks Nos. 50-53 sometimes on nest II 1,8 m distant from :･ A, No. S4 on two nests II and I 1.2 m from A, ptl R i l' s isb H while others on nests more than 4 m distant from A, e.g. No. 55 en X (July 6) and on A (July 5 ana ee 7).-No. 55 apparently had a wandering area west of li l1 1 llanNBInptNBIIx> m A as she was frequently found near the point 3 W. As nest X was at 7.0 WSW, she might have visited p i8S:i 1 lx-l it in the course of her wandering in her own area.

No. 56 was fbund on A (July 5) IX (July 6, 7, 9, 1O) R 1 F1 llnntr. 1 × l and X 12). IX and X were respectively 6.0 m b (July N.:gz)z:aZbz zazIB and m but only apart 7.0 distantfrom A 1.5m from : 1 limEimE. 1 l l each other. No. 57 was foun.d near A (July 6) on elbHtnB IX 7) and on VIII ll, 13). VIII was (July (July N 1 Hm)NCt)Pb1er.',)B- l 6.5 m distant frorn A but only 1.0 m from IX.･ -;8i Some seemed to have changed workers gradualIy se l H their hornes from A to other nests within their ..b. wandering area. For instance, No. 58 was found -B " st × on or near A, having a wandering area west to 1 1 l -BH

north-west of A until July 15, but she observed thth :.l･i was s･･E-b

on X on July 16-18 and at 4.5 W she was milking : 1o"'gob l l l 1 >IB

aphids on July 20, probably having changed her es-anZ:-l' . -3 H -co homg from A to X within or near her previous e 9 1 gz)z ijif1 1 p foraging area. No. 59 was observed near A on July fi M m 10 and 4 WSW on July 11 and 12. But she pear u 8 1 l1 1 1 H 1 1 o came out from V and VI when patted on July 18 s o ri=g -.l･ and respoctively. worker might also -8 21 This have .- 1 A Ah-shvmptutGeuk･osdin b 1 ttl l" 1 v- changed her home to nests within her wandering ch area. .- Hg-ij H m co 1 i l 1 i･] 1 b- t ut .L.NE

most essential causes in these il:: : polyethismof species. x t l ieglslo)lRl l 1 By rneans of mass marking under field condition, , OKLAND (1931) confirmed in E rnj?i the execution s"ptn l1g11xf1ort1cellg t's1Ieel1g by particular worker groups of some tasks, e,g. aphid milking, carriage of nest materials and trans- Ii 'rriates. port of colony DoBRzANsKA (l959) also E･et found a conservatism of aphid milkers in E rtijb by

observjng 27 individually marked workers for four

weeks under field conditions. She also stated that ing while other groups were capable of doing other aphid rnilking was rnore specialized than other tasks. In E yessensis, workers were apt to change tasks because in laboratory the milkers could not by aging their tasks from intranidal tasks to hunt- aocomplish any other tasks except for brood nurs- ing for larger workers and to milking aphids for

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VoL 28,No. 4 H pt k me \ ft su Dec. 1978

smaller one. About 80% of workers have a life visiting these nests, a change.of home nests does span of one year or 1ess, therefore, only 20% pass oocur because some marked workers were never through a second hibernation period to do extra- found on or near the previous nest after having nidal tasks in the next spring (HiGAsHi, l974, 1976). ence been found on other nests. Gradual change of In the present study each worker tended to remain home to nests within or near their foraging area is in a fixed task for some days. But conseryatism to suggested by examples such as Nos. 58 and 59, particular task varied among workers: Some though closer studies are neoessary to ascertain changed their task somewhat irregularly. Summa- how they change home nests.

Fizing, each worker is basically capable to do any

tasks but the degree of conservatism is different Symary

among workers. Thus, is by polyethism governed Conservatism to particular tasks or working differential conservatism to each task, younger areas and internest drifting of a polydornous red workers more confined to intranidal tasks while wood ant formica (I7brmica) yessensis FoREL wete older ones to extranidal ones, larger workers to studied in 1973 by marking 549 workers individual-

carrying nest materials, colony mates or foods Iy, with some additional observations in 1975. Tlie yrhile smalleT ones to digging or aphid milking. main results are : Some preyious authors reported foraging pat- l) Mest workers were conservatiye for some terns in various ants (6KLAND, 1931, EHRHARDT, days to oertain tasks such as milking aphids, intra-

19,31, HoLT, 1955, ScHwENKE, 19S7, DoBRzANsKA, or extranidal building. hunting, transport ofcolony 1958, 1959, WALus, 1964, RosENGREN, 1971, mates: 1972, 1973). HoRsTMANN, OKLAND(1931)mention- 2) Some workers carried out more than two limited ed the maintenanoe ef a area forhunting, tasks during the observation. Most workers might visiting nest materials aphid or gathering by par- be able to carry out rnost, if not all, tasks during ticular workers of F: rwfb, in an extreme case for their 1ife, though the dcgree of conservatism to each HoRsrmNN reported rediscovery 210 days. (1973) task is diflerent among workers. of 80--90% workers of Ii: on the same polyctena 3) The working area fbr each worker tended to tree even four weeks later. Observing some ant be limited during a certain period. [[1irough obser- species Dobrzanska (1958)distinguishedtwo for- yations for 17 days in July, most working･ areas aging patterns : 1) Each worker has her own hunt- were less than 4 m in di'ameter. In autumn the ing area even in the without any ant ground paths working area was smaller than in summer probably rtofZT, (jq: E pratensisRETz, E truncerum). 2) Such because of the inactivity due to the coldness. a hunting area is absent. A scout leads particular 4) Some workers seemed to have changed their souroe ant the nest mates to the food through paths home nests to those situated in or near their (M'yrmica scabrinodts, Tleiramorizam caespitum, foraging area. Leptothorax acervorum). E yessensis belongs to the fust type, each forager or hunter possessing a RefereDees limited area of 2 to 4 m in diameter witheut par- CzEcHowsKI, W. 1975. Bionomics Qf Fbrmica (Cbpto- ticUlar paths fbr a long time, though a few workers seernod to change their area within a short period. formica)pressilabrisN\L.(H),menoptera,Fbtmicidoe), Ann. Zool., Warszawa, 33: 103-126. internest drMing I]k)BRzANsKA, J. 1958, Partition of foraging ground and Some species of the formica are outstand- genus modes of conveying information among ants. Acta ing by the polydomous system in which a worker Biol. Exp., 18: 55-67. visits two or more nests (ScHERBA, 1961, 1964, 1959. Studies on the division of labour in ants TALBoT, 1961, G6sswALD, 1962, CzEcHowsKl, genus Fbrmica. thid,, 19: 57-81. EHRHARDT, S. 1931. Vber Arbeitsteilung bei M),rmica- 1975). In F: opaciventris EMERy ScHERBA (1964) und Mlessor-Arten. Z. Morph. Okol, Tiere, 20: 755- reported that O.5 to 5.4% of workers were redis- 812.GOsswALD, covered at other nests several days after marking at K. 1951. Die rote Waldameise im Dienste der one nest. In E yessensis, too, such drifting was Waldhygiene. Metta Kinau Verlag, Lilneburg, 1 oo pp. reported by ITo & IMAMuRA (1974). In the present 1962. AuBergewOhnliches Beuteverhalten unter study some workers were found on other nests not Nestern einer Ko]onie der Kleinen Rotcn Walda-

marked not easy there.Although itis to determine meise Fbrmica polyctena FORsTER (ll),menoptera: whether they changed their homes or were only316 FbrmicidZle). Beiter, Ent., 12: 615-631.

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VD1．28， No ，4 JAPANESE JOURNAL OF ECOLOGY Dec．，ユ978

G 伽 scH W ．1933．Untersuchungen − 1971 ， UberdieZusammen RosENGREN， R ．Route fidelity，visual memory and arbcit im Ameisenstaat． Z ． Morph ．6ko 呈． Tiere 28 ： recruitment ， behaviour in fbraging wood ants of thc − 319 401． Formica Fe 血 ca 133 二 1−106 genus ．Acta Zoologica ，． HIGAsHI， S．1974． Worker polyethism related with body ScHERBA， G 1961． Nest stnlc 重u 鵜 and reproduction in

size a red wood ant Fo 厂miea Formie the m α 皿 d−building ant Fo 厂 in polydomous ，（の mica opaciventris E ）一｛ERY アessensis FoR 肌． Jour． Fac． Sci． Hokkaido Univ． Ser， in WyomingJ ． N ． Y ． Ent ． S ．，69：71−87． − VI， Zoo1 ．， ig： 695 705 ． 1964．Analysis ofinter −ncst rnovement by workers 70rm 1976．Nest proliferation by budding and nest of the ant ∬ ’ca ｛脚 c ゴvent 厂is EMERY （Hy 〃tenoptera ： − growth pattem in Formica （Formica）アe ∬ ensis in Formicidaの． Animal Behavior XH ： 508 512． Ishikari Shore． lbid．20：359−389． ScHwENKE W ．1957． Ober die rauberische ，， Tatigkeitvon

HoLT ， SJ ．1955． On thc 『braging activity of the wood Formica rufa L ． und Formica nigricans EMERY auBer −

ant ，」。 Animal Eco1．24 ： 1− ． − − ， 34 halb einer InsektenMassenvermehnlng（Hymenop HoRsrMANN K 1972． Untersuchungel Nahrung − tera ：Formicidae Be 孟ter Ent 7 ：226−246 ， Uber ）．．．，． serwerb der Waldameis （Formica pelycte砌 S 皿 Tz ， H ．1939．＊ Die Tiefwelt Deutschlands ．37 Tei且． FoERs皿 R ） im Eichenwald． II， Abhiingigkeit vom Hymeneptera Fomicidae． Verlag von Gustav Fisher． Jahresverlauf und vom Nahnmgsangebot． Oecologia Berlin．

− （Berl．），8； 371 390． TALIx）T ， M ．196L Mounds of theant Fo 厂mica utkei at

．【suchungen zu 【見mter ， Geofge Reserve Livi 1973 Unte Arbeitsteilung theEdwin S ， ston County， den AuBendienstarbei加 dnnen der Waldameise Michiga皿． Ecol．42： 202−205． For〃ゴcapotyctena FoERsTER ．Z ． Ti（）sychoL 32：532− WALLrs D ． L 1964． The foraging behaVior of the ant 珂，，， − 543， For〃lica fus【ra． Behavior，23： 149 176．

IMAMuRA S ．1974． Observations on the hibemation of a 拿 in ．， Cited ITO，M （1973）．

ant Formica Formicd e ∬ ensis 肌 polydomous ，（）ア FoR ，

Jour Fac Sci Hokkaido Univ VI Zoo1 19 ：．．．．Ser．，．，摘要 438−444 ，石狩海岸には，10km 以上に渡ってエゾアカヤマァリ ITo， M ．1971． Nest distdbution of Formica ye ∬ elzsis Formica （Formic の yessensis FOREL の巨大な融合コ FoREL in Ishikari ShOre， in reference to plant 2かロニーが見られる．今回はこのコロニー内での各ハタラ nation ． Ibid．，18： 144−154．キアリの巣外行動を調べるために個体マーク法を用いて 1973． Seasonal population trends and nest 次の結果を得た． in a ant Fo 厂〃 lica Formica structure polydomous ，（） 1）ほとんどのハタラキアリは，アブラムシの世話， FOREL Ibid 19： 270 −293 アessensis ．，．ハンン巣内外での巣造り，ティグ，他の個体の運搬など＆ IMAMuRA， S．1974． Observation on the nuptia1 のうち，ある一定の仕事を数日間続ける傾向を示した， ight and 量nternlda 】relationship in a 】 ant 且 po ydomous ， − 2）しかし，いくらかの個体は複数の仕事に従事し Formica （Fo 厂〃〜’c のyessens’s FOR 肌． Ibid．，19：681 694．一た．恐らく，ある定の仕事に対して特殊化してしまっ KIIL， V ．1934． Untersuchungen Uber Arbeitsteilung bei たような個体を除いて多くのハタラキアリはほとんどの Ameisen 」Formica 厂 L （ramponotus （ ψ ， herculeanus − 仕事を行ないうるものと思われるが，各仕事に対する嗜 L ．und C ．’ignipe厂da LATR ．）Bio1． ZbL ，54 ： 114 146．好性及び固執性に個体間で程度の差があるために分業が OKIAND， Fr．1931．Studien Uber die Arbeitsb巳ilung d 生じているようである． die Ten1皿 g der Arbeitsgebiotes der roten Waldameise 3）ほとんどのハタラキアリは，数日間，各自に定ま（F．rufa L ．）． Z ． Molph ．6kol。 Tiere，20： 63−131．った仕事域を訪ずれる傾向をしたの日にも示．7 月 17 間 Om ， D ．1958． OberdieArbeitsteilungim Staatevon − 渡る観察ではほとんどの個体が直径 4m 以内の仕事域を Form ’ca r ψ rufo pratθnsi3 雇〃 or G6ssw ， und ihre 維持した．9 月には 7 月に比べて仕事域が縮小した． verhalte 且 sphysio 量ogischen G 田 ndlagen ： E 血 Beitrag 4 いつのの）くか個体はもともと自分仕事域内か，そ zur Biologie der Roten Waldameise． Wiss． Abh ．，30：の近辺にあったへりむよになった． 1−166．巣移住う

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