The LepidopterologicalSocietyLepidopterological Society of Japan

uetma Trans. tepid. Soc. Jtipan 60 (2): 152-160, March 2009

Eilic)ets of Cleltis sinensis and euercus acutissima afforested area on a population of the near-threatened butterfly, Sasakia charonda (Lepidoptera, Nymphalidae) in central Japan

rlakato KoBAyAsmi'*, Masahiko KiTAHARA') and [Ibhm NAKAsHizuKA2)

`)Laborutory of Animal Ecolegy, Yamanashi Institute of Environmenta1 Sciences, 5597-1 Kcnmarubi, Kamiyoshida, Fujiyoshida, Yamanashi, 403-OO05 Japan " Graduate School of Life Sciences, Tohoku University, Aoba 6-3, Ar2tmaki, Aoba-ku, Sendai, 980- 8578 Jap an

Abstract To clarify the distribution patterns of resource plants suitablc for conserving Sasakia charondl:, we investigatcd the densities and sizes ofboth 1arval host trees, Cettis sinensis, and trees which serve as an adult food resource, 2uerc/us acutissima, as well as the number of ovcrwinteritig S. charostda larvae per host trce at an area planted with a mix of C. s'inensih' and C, acutissima for preserving S. charonda and in thc surrounding area ofnutural forests. In the atlbrested area, scvcral of the C. sinensis trees planted in the center withered and died, whilc none of the 2. ac"tissima trees died. Dbh (diameter of breast height) of C. sinen.s'is at the edge of thc aff'orested area was signjficanlly 1arger than that at the intcrior, and simi]ar to tliat in the surrounding area of natural forests. In {he surruunding natural forests, dbh of C. sinensis at the edge was also significantly larg- er than that at the intcrior. The number of overwintering 1arvac was significantly smaller in thc af forcsted area than in the natural forests. In both the at:fbrested area and thc natural forests, the num- ber or overwintering larvae was significantly greater at the edge than in the interior, However, no significant dil]k]rcnces were found in lhe "umber of ovcrwintering ]arvae between thc cdge of the afforested area and in thc natural forests. For conservation of S. charonda, it is suggested thur 2. ac"tissima trees should be planted in the interLer of a planned afforestatien area and C. sinensis sheuld bc planted at the edge of the affOrestation area.

Key words Sa,s'akia charonda, host trees, adult fOod resourcc, ufforestation, edges of forests, con- servatlon.

Introduction

[Ib conserve populations of rare organisms, especially those experiencing dramatic habitat loss, it is essential to restore the habitats with arrangements of their resources suitable for maintaining their populations. [[b do this, it is necessary to first claiify the effective arrangements of resources for conserving the populations. HQwever, few attempts have yet been made to undertake conservation activities for endangered species based on such scien-

ti fic knowledge,

In Japan, the giant purple emperor, Sasakia charvndti (Lepidoptera, Nymphalidae), is a symbolic insect known as the country's natienal butterfiy. At one time, the species was very common in secondary broadleaf deciduous forests and riparian forests almost all over the country. However, since Japan's period ef rapid economic growth, populations of the species have declined mostly due to deforcstation associated with changes in land use such as construction of roads and buildings, and the resultant decrease in the numbers of their host trees, Cegtis sinensis, and Cettis .iessoensis (Higuchi & Sato 1987). Consequently, S,

*Cerrcspondingauthor:[email protected]

Contact address: K-1O1, 2-2-18 Umezene, Tsukuba, Ibaragi, 305-O045 Japan

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153 EtTects of afforested Area on Sasakia charonda

charonda is now designated as a near-threatened insect in Japan (Ministry of the Environment 2006), and conservation efforts for the butterfly have been initiated in various localities around the country.

Usual].y as part of these efforts, C. sinensis or C. jessoensis, which are host trees of the lar- 'food vue, and ettereus act{tissima, whose sap is a major resource for the adu]ts in central Japan (Fukuda et al. 1983), are planted in the habgtats. However, few attempts have yet been made to evaluate how S. charondtt uses these resource-related trees thaL are planted. Therefore, most conservation efforts are carried out with little basis in scientific knowledge and information.

An area located on Shichirigaiwa plateau, Hokuto City, Yamanashi Prefecture, central Japan, was afforested by planting with C. sinensis and e. acutissima side by side fbr the purpose of preserving S. charonda populations (hereafter, the afforested area), However, no attempts have yet been made to examine how the tilibrested area is utilized by the butterfly, and whethcr thc area is helpfu1 to maintenance of its populations. In the present study, wc investigate the current status of an atforested area created for the purpose of preserving S. charonda populations, and examined how the area is utilized by the butterfly as a case study.The

main purposcs of this study were to examine how S, charonda populations use the atforested area, and as a result, to clari'fy hew to afforest their resource-related trees in a suitable and effective way for conserving the populations of S. charonda.

Life history of S. charoncla

S. charondu is distributed over the mountainous regions of northern [faiwan, continental China, the Korean Peninsula, and Japan. In Japan, S. charonda is univoltine and the host trees are C. sinensis or C.,iessoensis. On the Kanto Plain ofcentral Japan, the flight season of adults extends from late June to late August. The minimum duration of the egg stage is five days (Kobayashi & Inaizumi, 2002). Larvae feed on leaves until the end of 0ctober, when they reach the 3rd or 4th instar. They descend the trees early in November and over- winter in the litter near tree tmnks. In early spring of the fo11owing year, they return to the budding trees, finish their developmcnt there and pupate in June.

Study area

At the gentle slope on Shichirigaiwa Tbrrace facing Kamanashi River, in Hokuto City, Yamanashi Prefecturc, central Japan, natural forests consisted of canopy trees of Pinus densij7ora, C. sinensis, C. jessoensis, .htglans mandshurica and Zelkova serrata which are widely distributed (Fig. 1). In particular, many larval host trees o'f S. charonda, C. sinensis or C, jessoensis, are found at landslide sites of the slope, and the density is 50.0 treeslha (Kobayashi et al. 2008), Also on the slope, there is an area planted with a mixture of C. sinensis and e. acutissima side by side (hereafter, the a'fforested area), which was afforested for the sole purpose of preserving S. charonda popu]ations under the government of Nagasaka-[[bwn (Hokuto City at present). That is, the sequence of C, sinensis and the se- quence of e. ac"tissima are arranged in a]ternating rows (Fig, 2). In the a'ffbrested emrea (about 4.0 ha), thc planting interval of C. sinensis and e. ac"tissima is 2 m (Fig. 2). The C 'i.n sinensis and e, acutissima were both about 1 m in height when planted the area in 1982, and therefore, their age is currently estimated to be at least more than 26 years (Hasegawa, unpublished data). The alfbrested area faces a paved (asphalt-surfaced) road and only C. sinensis trees are planted at the edge of the area frLcing the road (Fig, 2). The other edges of the afforested area are in contact with natural forests. Thus, in this paper, only the trees fac-

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． ・ 154 Takato KoBAYAsHI， M asahiko K1 rAHARA and Tohru NAKAs 田 zuKA

〕Oln 」 一 一 L 』

Fig ．1． The research site of this study was a gently sloped area on ShichiTigaiwa Terrace facing

Kamanashi River， in Hokuto City， Yamamashi Prefecture， central Japan．

广

Ed

一 呂 靄

40伽 ○ （）θ2tis sineηsis ■ QuerCUS acuti5S’ma 囲 Natural Foresヒs

Fig ．2． Mimetic diagram of the affforested urca planted with C ． sinen ，yis and 2．σ α 傭 3 吻 α side by side for the puq ）ose of protcction of S． charonda in the upPer part f a gen しly sloped area on Shichirigaiwa Terrace．

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Etfects of aifbrested Area on Sasakia charoncla 155

ing the pasJed road of the afforested area are treated as the forest edge of the area (Fig. 2),

Materials and methods

1) Density and dbh of C. sinensis and e. acutissima in the affbrested area

The densities of C. sinensis and e. acutissima were examined in the atforested area in May, 2003, Tb clarify the difference in the sizes between C. sinensis trees and e. acutissima in the afibrested area, we measured the dbh of 30 trees selected randomly in each area.

2) Number of overwintering larvae of S. charenda and dbh of C. sinensis both in the

alforested area and in the surrounding area of natural forests

[[b compare the size of C. sinensis trees in the affbrested area and in the surrounding urea of natural fbrests, we measured dbh of 30 trees of C. sinensis randomly selected from each of the afforested area and the surrounding area ofnatural forests. During 15-28 December in 2003, we co]lected litter at the forest floor within a range of O.5 m from the base of the 30 trees selected from each of the afforegted area and the surrounding area of natural forest, and immediately counted the number of S. charondo larvae in each sampie of coliected lit- ter at our laboratory. The stage of the larvae was third or fourt1i instai: ln addition, we se- lected 1 1 C. sinensis trees from the 30 trees selected from the afforested area, which grew at the edge of the allbrested area, and 30 host trees in the surrounding area of natural forest; we compared dbh of C, sinensis and the number of S. charonda overwintering larvae be- tween them.

3) Comparisons of the size of C sineitsis and the number of S. charontla oyerwintering Earyae between at the edge and in the interior of the afforested area

Tb clarify the distribution patterns of the 1arvae in the afforested area, we selected 1 1 host trees, which grew at the edge of the afforested area, and 19 host trees in the interior of the atibrested area, and compared the number o'f larvae and dbh of host trees between them.

4) Size of C. sinensis trees and the number of overwintering laryae both at the edge and in the interior of the surrounding natural forest

rfo compare the number of overwintering S, chaivndce larvae and the size of C. sinensis trees between the edge and the interior ofthe natural forests facing an asphalt road, we randQm]y selected 30 C. sinensis trees both at the edge and in the interior of natural fbrests during 15- 28 December in 2003, and compared the number of larvae and dbh of host trees between them,

Results

1) Density and dbh of C. sinensis and e. acutissima in the affbrested area

In the aiforested area, a portion of the C. sinensis trees planted in the center withered and died, while none of the e. acutissima trees died. In the afforested area, the densities of C. sinensis and e. acutissima were 5,OOO trees per 1 ha, including a sma]1 number of withered C. sinensis trees. In the fbrest interior of the area, the dbh of e. ac"tissima was significantly 1arger than that of C. sinensis (Tlable 1 ).

2) Number of everwintering larvae of S. charontla and dbh of C. sinensis both in the affbrested area and in the surrounding area of natural forests

The dbh of C, sinensis in the alk)rested area was significantly smaller than that in the sur-

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156 Takato KoBAyAsHt, M ttsahiko Kt'rAH.xR,x and Tohru NAKAsHTzuKA

Table 1. Dbh`) of C. sinen,sib' and e. acutissima in thc affbrested area.

C. sinens'is . acutisslnwlP]) Number of trees investigated 3042 30122

Avera e of dbh (min) ± 35 ± 33P

i'Diameter of breast height. !)Mann-Whitney U-test.

rounding area of natural forest ([Ihblc 2). However, the dbh of only C. sinensis trees at thc forest edge of the alforested area was not significantly dilferent from that in the surrounding area (rfable 3), The proportion of C. sinensis trees at which the overwintering ]arvae were fbund was significantly lower in the afforested area than in the surrounding area of natural forests (Table 2). The number of overwinteting larvae per host tree was also significantly lower in the afforested area than in the surrounding area of natural forests (Tbble 2). However, the proportion of C. sinensis trees at which the overwintcring larvae were found was not significantly different between the edge of the affbrested area and the surrounding area of natural forests (Tab]e 3). No significant ditferences werc fbund in the number of overwinterjng larvae per host tree between the edge of the afforested area and the surround- ing area of natural forests (Table 3).

3) Size of C. sinensis trees and the number of overwintering larvae at the edge and in the interior of the affbrested area

The average dbh of C. sinensis trees at the edge of the afforested area was significantly 1arg- er than that at the interior of the arca ([Rible 4), The proportion of C sinensis trees at which the overwintering 1arvae were found was significantly higher at the edge than in the interior of the alibrested area ([[hblc 4). The number of overwintering larvae per host tree was also significantly greatcr at the edge than in the interior of the afforested area ([fablc 4). 0n May 20, 2003, we observed 1 5 fifth instar larvtte on a host tree with 1O mm dbh and a height of 2 m in the interior of the afforested area. This number o'f 1arvae observed (15) was rather high compared with the average number of overwintering 1arvae in the interior of the aiforested area (1.3). At the same time, we observed that almost all leaves were lost from the host tree probably, due to the foraging of the larvae, and most of the larvae had moved fi'om the upperpart to the lower part of the tree. However, they never fell down to the ground and re- peatedly moved up and down along the trunk. After two days, we observed no larvae on the 'four tree. During the two days, we observed the predation of 1urvae on the tree by folistes snelleni,

4) Size of C. sinensis and the number of overwintering larvae both at the edge and in the interior of the surrounding area of natural forests

The average dbh of C. sinensis trees was significantly 1arger at the edge than in the interior of the area of natural fQrests (rlhble 5). Thc proportion of C. sinensis trees at which the overwintcring larvae were found was 1OO% both at the edge and in the interior oi' the area of natural forests (Table 5). However, the number of overwintering larvae per hest tree was significantly bigher at the edge than in the interior of the area of natural forests (Table 5),

Discussion

Growth patterns of C. sinensis and 2. acutissima trees in the afforested area

At least in the plantation method w]'th a mixture of C. sinensis and e, ac"tissimci at a density of 5,OOO treeslha of this study, C. sinensis seemed to lose out in competition with e. acutis- sima,

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157 Effects of afforested Area Qn Sasakia charonda

Table 2. Number of Sasakia charonda laryae per hest trcc and sizc of Cettis sinensis in natural ferest and the affbrested area.

Natural fbrest Afforestcd arcaP

Num ber of trees investigated 30 3014 Number of host trees on which ]arvae were discovered (%)3)25 C83%) (47%) P

')Fisher'sexacttest.

Z)Mann-Whitney U-test. "'Percentage ef numbers of trees where larvae were found to total number of trees investigated. 4J Diarneter of brcast height.

Tublc 3. Number of Sasakia eharonde larvae per host tree and size of Celtis sinensis in narural forest and edge of rhe afforested area. Naturaiforest Egg?.gf.tdh?,,eaP Number of trees investigated 3025 M10 Number of hest trees on which larvae were diseovered (%)') (83%) (91%) P=O.44i) Number of 1arvae per host tree 13,7± 1.6.6 5.7±2.2I12 P=O.17!) Avera e dbh`' ofhosttreeinvesti ated mm) 172± 100 ± 22 P=:O.102) i)Fishcr'scxacttest.

2) Mann-Whitncy U-tcst. 3)Percentage of numbers of trees where 1arvae were found to tota1 number ef trees investigated. `) Diameter of breast height.

Table 4, Number of Sasakia charonda larvae pcr host tree and size of Celtis sinensis on cdge and jnside of the alI/orested area.

Edgc of the Interier of the afforestedarea alIoresLcdareaF

Number of trees investigatcd 1110 193(16%)1,3 Number of host trees on which 1arvae wcrc discovered (%)3' C91%) P

2]Mann-Whitney U-test. i)Percentage of numbers of trees where [arvae were found to total number of trees investigated. `)Diarneter of breast height.

Table 5. Number of Sasakia charonda larvae per host trcc and size of Celiis sinensis on edgc and inside of the natural forest.

Edge of the lnterior of the P afforested area afforested area

Number ef trees invcstigated 30re' 3030 Number of host trees on which larvae were discovered (wr,)?i30 (1 OO%) (100%) Nuinber of 1arvae per host tree 69.8± 34.2 46.7± 28.9 P

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158 Takato KoBAyAsm, Masahiko K"/AHARA and Tohru NAithsmzuKA

Why was tho growth of C. si.nensis lower in the intcrior of the atforested area than at the fOrest edge?･ This was probably because C. sinensis growing not only in the interior of the forest but also at the forest edge lost out to e. acutissima on the pltmtation method with a mixture of C. sinensis and e. acttttssima at a density of 5,OOe treeslha. C. sinensis trees planted at the forest edge received more sun]ight than those in the interior of the forest, and could thus grow 1arger. The growth of C. sinensis planted in the interior o'f the forest was poor, prebably because of the covering by e. acLttissima. The reason why C, sinensis lest out to e, acutissima under the condition of co-planting at the high dcnsity in this study area 'former may be because the requires more sunlight tban the latter.

Larval distribution patterns in the atforested area 'in It was found this study that the size of C. sinensis was 1arger at the forest edge than in its interior, and the number of overwintering larvae of S. charondu per tree was greater in the fbrmer than in the latter, both being observed in the ailiorestated area (Table 4) and natural 'for forests (TleLble 5). From these obscrvations, the optimal environment 1arvae of S. chaFvn- dn was considered to be the fbrest edge.

Why was the number of overwintering larvae larger on C, sinensis trees ttt forest edgc than in the interior of the fbrest? Firstly, both in secondary and natural forests, C. sinensis were larger at the forest edge than in its interior, and the number of overwintering 1arvae per tree was greater in larger trees, It was indicated that in secondary forests of e. acutissima and e. seratta as well as in natural fbrests near the study site, the number of overwintering lar- vae incrcased with the size of C. sinensis (Kobayashi et al., 20e8), In the present study, we encountered a smaH C. sinensis tree with many larvae, but, ]ater, nolle were found on the tree, probably because of overgrazing and predation (observation on 20 May, 2003).

The second major reason may be the activity range of adult S. charonda and the mortality of larvae from hatching to immediately before wintering. In a previous study (Kobayashi et al,, 2008), we reported that the fOrest edge rather than the interior is the main activity range of adult butterflies of S. charonda, and the numbers of adult males defendin.o their territo- ries and that of adult butterilies courting, mating, and laying eggs were significantly larger 'forests at the fOrest edge than in the interior of the natural and secondary ]ocated near the present study area. The number of eggs Iaid at the forest edge may alse be larger than that in the interior of the forests. In previous studies (Kobayashi and Kitahara, 2005; Kobayashi and Inaizuini, 2002), we reported that the number of eggs laid by adult S. charonda per C. sinensis tree planted at the small patches of secondary forests or at the center of grasslands, which are outside of the activity range of this species, was small, and that of overwintering 1arvae per tree was also small due to a high mortality rate of larvae from hatching to imme- diately befbre wintering Cmid-fourth instar) as a result of marked predatien pressure. On the other hand, within the activity range of this species, the number of eggs 1aid was 1arge, , and the mortality rate of larvac per tree fi"om hatching to immediately befbre wintering was low, resulting in a ]arge number of overwintering larvae. Similarly, the number ef laid eggs may bc small and the mortality rate of larvae may be high in the interior of the fbrests, which is outside of the activity range of adult butte[flies.

Will thc number of adult butterflies be large if there are many 1arvae? Previously, we re- ported that the number of male and female adult buttcrfiics was large around trees on which the number of ovcrwintering larvae per tree had been ]arge, and vice versa (Kobayashi et at., 2oo4, 2oos).

For thc above reasons, the number of overwintering larvae and, consequen tly, the number ef emerging butterfiies of S. charondu, were larger at the forest edge than in its interior, and

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E'ffects of atfbrested Area on Sasakia charonda 159

these numbers of host trees at the forest edge will help in the maintenance of the population of this species.

AffOrestation technique suitable for conservation of S. charontla populations suggested by the present study

In this study, the diameter at the breast height (dbh) was larger in e. acutissima than in C. sinensis. What significance does this observation haye on the presence of S. charonda? In the interior ef affbrestation areas, C. sinensis is shaded by e. ac"tissima, and cannot grow to the height required to form canopies. Under this condition, C. sinensis is often small, grows poorly, or even dies. On small host trees in the intetior of forests, the number of 1ar- vae per tree and the number of emerging butterflies will be smull. TherefOre, a plantation method with a mixture of C. sinensis and e. acutissima will result in the poor growth of the former and, consequently, the number of S. charonda per tree will decrease.

What is afforestation technique is indicated by the present study as being suitable fbr con- servation of S, charonda populations? First, as in the present afforested area, it is necessary that the trees of C. sinensis and 2. acbttissima are both planted in a planned afl]orestation area, because the fbrmer is a main 1arval host tree species, and was in fact utilized by the larvae of S. chaTvndd in the present area, and the sap of the latter is a major food resource (Fukuda et al. 1983, Kobayashi & Jnaizumi 2003, Kobayashi & Kitahara 2005), and was in- deed utilized by the adults in present area (Kobayashi et al., 2008).

Second, it is necessary that the host trees of C, sinensis are mainly planted at the edge of a planes afibrestation area and e. acutissima trees planted in the interior of the alibrestaLion area, because the present study showed that C. sinensis trees planted in the interior of the afforested area ceuld not mature into large trees and could not form a canopy, and a por- tion of them withered and died, probably due to the competition with e. acutissima trees ([Ihbles 1 and 4). In addition, it was also found that C. sinensis trees planted in the interior of the atfbrested area were rarely utilized or not utilized at all by the larvae of S. charonda. Moreover, another study pointed out that adults of S. charonda are more active at the forest edges than in thc interior (Kobayashi et al., 2008), and thus, there is a possibility that C. sinensis trees planted in forest interior are not used as much by the adults as by the larval host,

According to the discussion presented above, in the case of making good use of a plantation of C. acutissima and euerc"s serrata which already exists, it would be better for the host 'for trees of C, sinensis to be planted at the edge of the plantation conservation of S. charonda populations.

Acknowledgments

We express sincere thanks to Professor Dr Hikaru Kitahara, Shinshu University, and Dr Takenari Inoue of Forestry and Forest Products Research Institute fbr their usefu1 comments on this study.

References

Higuchi H. and K, Sato, 1987. Distribution of Sasakia charonda Hewitson in Tochigi PrcfCcture. Bull. Tbchig. ipref Mus. 4: 7-14 Fukuda H., Hama E., Kuzuya K., Takahashi A., Takahashi M., Tanaka B., Tanaka H., Wakabayashi M. and Y, Watanabe, 1983. T:lie L4fe HistoslF qfButteijlies in JZu)an 2. Heikusha, Osaka. (In Japancsc with English abstract). Kobayashj T. and M. Inaizumi, 2002. Ditference in mortality rates and factors of irnmatures before overwin-

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160 Takato KoBAYAsHi ， Masahiko KITAHARへ and Tohru NAKAsHIzuKA

te曲 of tho NynlphalidButterflySasakia charon ‘’ − g ， ‘1 （HewiIson）， in relation to vege しa 巳on shift surround ing the hQs毛 ．ノα − plants 1λ ノ！Ent．〔N ． S．）5 ： 35 49 （inJapanese with English刃ummaly ）． 2003 ・ ・The sex ratios of the wild adult populations in Sasakia charonda （Nymphalidae）．Trans． ・ − lel）id． Soc．ノapan 54 ： 156 162 ． Kobayashi T ．and M ． Kitahara，2005 ． E 仔ect of s し叮 ounding vegetation oll the oviposition pre1ヒrcnce of − Sasakia char θ nda （Lepidoptera： Nymphalidae）．」． Forest ’ぜes ，10 ： 167 172， Kobayashi T ．Nakashizuka T ．Kitahara M ．Kubo ， ， ， M ． and S． Ito，2008． Roles of 卯 arian and secondary − forests in maintainjng the near threatened buしtcrfiy，∫α∫ α左fα ‘加 ro η 4α （1．epidoptcra ， Nymphalidae − ’ ）popu Iations in Japan． Eco ’．1〜e ，s ．23： 493−502 ． ’ Kobayashi T ．， Tanimoto T ． and M ．Kitah趾 a ，2004 ， Relationship between rate of forest urea and the densitics of the nympha ［id butLじrfly ， Sasakia charo ’ヱda Hewitson ， and the host trces， Celds sinells 重s Persoon ln ’ （ Japanese with EIlglish sunlmary ．ノap ．ノ， Co，lselv ， Ecol．9： 1−12． ） ’ MinistryQf thc Envifonment20 ‘ ’ ア − 〔〕6． Insecta． Threatened Wi1ill1L of Jalα n Red Data Bo ‘丿k （2nd Edn ）5 、 246pp ．亅apan Wi ］dlife Rescach Center， Tokyo ．

摘 要

エ ノ キ と ク ヌ ギ の 植林が オ オ ム ラ サ キ の 個 体 群 に 及 ぼ す 影響 （小 林 隆 人 ・北 原 正 彦 ・中 静 透 ）

オ オ ム ラ サ キ の 個体 群 を保 全 す る 冖的 で 餌植物 の 植林 を行 う1祭の 効 果 的 な植 林 方 法 を 明 らか に す る た め ．本種 の 保 護 を 目的 と し て ク ヌ ギ と エ ノ キ が 交互 に列 状 に植 林 され た場所 とそ の 周 囲の 天 然林 ・ で ，エ ノ キ と ク ヌ ギ の 密度 大 き さ ，オ オ ム ラ サ キ 幼 虫 の 木 当た り密度 を 調べ た ．植林 区林 内 で は 枯 エ ノ 死 した キ が あ る 程 度見 ら れ た が ，ク ヌ ギ の 枯 死 は 見 られ なか っ た ．植 林区 の エ ノ キ の dbh （胸 高直

の の エ ノ エ 径）は 周 囲 天然 林 キ よ りも有 意 に 小 さ か っ た ．し か し，植 林 区 の 林 縁 の ノ キ に 限 っ て は、dbh は の エ ノ キ よ エ ノ 林 内 りも大 き く，周 囲 の 天 然林 の キ と差 が な か っ た ．周 囲 の 天 然林 に お い て も，林 縁 の エ ノ キ の dbh は 林 内 の エ ノ キ よ りも大 き か っ た，植 林 区 の エ ノ キ に お け る 木当 た り幼 虫数 は 天 然 林 よ りも有 意 に 少 な か っ た ．植 林 区 で も周 囲 の 天 然林 で も木 当 た り幼 虫数 は 林 内 よ り も林 縁 で 有 意

っ ． エ に多か た た だ し， 植林区 の 林縁 の ノ キ に お け る 木 当 た り幼 虫 数 は 大 然林 の 木 当た り幼虫数 と有意 に 異 な らな か っ た ． を す る に は の に ヌ エ ノ べ 本種 保護 植 林 予 定 地 内 部 ク ギ を ， 林縁 に キ を植 える きで あ る ，

（Acceptecl December 16，20 〔｝8）

Published by the Lepidopterological Society ef Japan ， − − 5 20， Motoyokoyama 2， Hachioji， Tokyo ，192 eO63 Japan

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