Bull. Natl. Mus. Nat. Sci., Ser. A, 42(1), pp. 49–54, February 22, 2016

Host Plant, Larva and Life History of Asiemphytus fasciatus(Hymenoptera: Tenthredinidae) in Japan
Akihiko Shinohara1 and Shin-ichi Ibuki2
1

Department of Zoology, National Museum of Nature and Science,
4–1–1 Amakubo, Tsukuba, Ibaraki, 305–0005 Japan
E-mail: shinohar@kahaku.go.jp
2
Wami 1355–13, Nakagawa, Tochigi, 324–0612 Japan
E-mail: banbi-fa@ktd.biglobe.ne.jp(Received 29 October 2015; accepted 22 December 2015)

Abstract Based on observations and rearing experiments in Nakagawa Town, Tochigi Prefecture, Honshu, in 2015, the host plant and life history of a tenthredinid sawﬂy, Asiemphytus fasciatus (Takeuchi, 1929), are recorded and the larvae are described. The sawﬂy probably has three
generations a year in Nakagawa and the larvae are solitary external feeders on the leaves of Cornus controversa (Cornaceae). The mature larva enters rotten wood, not soil, for the prepupal andpupal stages.
Key words : Hymenoptera, Tenthredinidae, Asiemphytus fasciatus, host plant, larva, life history,
Cornus controversa, Japan.

Introduction
Asiemphytus fasciatus (Takeuchi, 1929)(Hymenoptera, Tenthredinidae) is a sawﬂywidely distributed in Hokkaido, Honshu, Shikoku and Kyushu, Japan (Abe and Togashi,1989). It is an uncommon species and the hostplant and life history were unknown. In 2015,
Ibuki was able to rear this sawﬂy from larvae
feeding on Cornus controversa Hemsl. ex Prain.
(Cornaceae) in Nakagawa Town in Tochigi Prefecture, central Honshu, Japan.
Here we give the rearing records, the ﬁrst hostplant record, and a brief description of the larva.
The new host record, Cornus for an Asiemphytus
species, was quite unexpected, because the threeother known Japanese species of Asiemphytus are
all associated with Deutzia crenata Siebold etZucc. (Hydrangeaceae) (Okutani, 1967).
Materials and methods
The material used in this work is kept in the
National Museum of Nature and Science, Tsu-kuba. Four groups of larvae, with the group
codes SI150604 (eight larvae), SI150609 (fourlarvae and the offspring of one of them),
SI150707 (one larva) and S15I0920 (one larva)
were collected in the ﬁeld and reared (Fig. 12) ina room at Bambi Farm in Wami (N36°47′
E140°10′, about 240 m alt.), Nakagawa Town,
Tochigi Prefecture. The temperature and day
length were not controlled in the room, but thelight was usually on for about 16 hours a day. All
the photographs were taken by Ibuki with a
Ricoh GR Digital II camera. The digital images
were processed and arranged with Adobe Photoshop Elements 12 software. For the larval morphological terminology, we followed Viitasaari(2002).
Results
Reared specimens examined. 2♀1♂, Koisago, 125 m, N36°47′ E140°08′, Nakagawa Town,
larva collected 4. VI. 2015, matured 9. IV.,emerged 6. VII., host: Cornus controversa, S.
Ibuki; 1♀, Oyamada, 210 m, N36°48′ E140°13′,

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Akihiko Shinohara and Shin-ichi Ibuki

Nakagawa Town, larva collected 9. VI. 2015,
matured 25. IV., emerged 19. VII., host: Cornus
controversa, S. Ibuki; 2♀1♂, same data but
matured 27. IV.–2. VII., emerged 20. VII.; 7♂,
same locality, eggs laid 20, 21. VII. 2015,
matured 8, 9. VIII., emerged 26. VIII., host: Cornus controversa, S. Ibuki; 1♂, same data but
emerged 28. VIII.
Host plant. Cornaceae: Cornus controversa
Hemsl. ex Prain.
Field observations and rearing records. Fig.
12 shows rearing records in Nakagawa Town,
Tochigi Prefecture in 2015. On June 4, Ibuki
found eight larvae (SI150604) feeding on theleaves of Cornus controversa in Koisago. Of
these, ﬁve reached maturity on June 9 and three
on June 11. All larvae went into a piece of rotten
wood. Two female and one male adults emergedon July 6 from the larvae that matured on June 9.
The others died.
On June 9, Ibuki found four larvae (SI150609)
feeding on the host plant in Oyamada. Of these,
one each matured on June 25, 27, and July 1 and2. They all entered a piece of rotten wood. One
female adult emerged on July 19 from the larva
that matured on June 25, and two female and one
male adults emerged on July 20 from the larvaethat matured on June 27 and July 1 and 2. One of
the female adults that emerged on July 20 laid 15
eggs into three leaves (one egg, three eggs, and11 eggs, respectively) on July 20 to 21 and they
all hatched on July 25 to 26 (the offspring of
SI150609). All the larvae matured and enteredrotten wood on August 8 to 9. The rearing container was not examined until August 26, whenseven male adults were found in the container; afew were alive but others were dead, suggestingthat the emergence occurred about a week before
August 26. An additional two males emerged on
August 28, and one male on September 19. The
remaining ﬁve individuals did not emerge before
October 25 and probably died.
On July 7, Ibuki found a larva (SI150707)
feeding on Cornus controversa in Wami. It
matured on July 13 and was preserved in ethanol.
On September 20, Ibuki found a larva(SI150920) feeding on Cornus controversa in
Wami. It reached maturity on October 2, but thelarva was kept in a container only with soil,
where the larva stayed on the surface of the soil
and never entered the soil. On October 5, a pieceof rotten wood was put in the container and thelarva immediately entered the rotten wood.
Both in Koisago and Oyamada, the larvae
were found on lower branches of young trees
growing along small streams in rather dark forests. Eggs were laid into the leaf tissue of thehost plant, usually in a small group (Figs. 1, 2).
The larva fed on the leaf solitarily and often
assumed a coiled resting position (Figs. 3–7).
The young larva stayed on the underside of theleaf and fed on the surface cuticle of the leaf
(Fig. 3). On maturity (Fig. 11), the larva enteredrotten wood and stayed in a cavity inside the rotten wood without making a cocoon.
Description of the larvae. First and 2nd instars(Figs. 3, 4): translucent creamy white; head withpale bluish-gray tint posteriorly. Third instar(Figs. 5, 6): similar to 1st/2nd instars, but head
more extensively darkened and median abdominal segments each with very small black spot insupraspiracular region. Fourth instar (Fig. 7):
similar to 3rd instar, but dorsum of head mostly
pale bluish gray and black spot on each abdominal segment larger. Last feeding instar (probablyﬁfth) (Figs. 8–10): about 15 mm long; head dark
bluish gray with ventral part dark olive gray;trunk creamy white, with dark bluish tint inside
dorsally and often slightly orange tint ventrally;
paired spots (large anterior one and small posterior one) on supraspiracular region of mesothorax, metathorax and 1st to 8th abdominal segments and small spot near anterior margin of 9th
abdominal segment black. For each feeding
instar, entirely covered with wax and consequently appearing whitish, except just after molting (Figs. 5, 8). Prepupa (Fig. 11) similar to lastfeeding instar, but ground color dark bluish graydorsally, dark creamy white along spiracularregion, and dirty pale orange ventrally and on
prothorax, without wax covering.

Biology of Asiemphytus fasciatus

51

Figs. 1–11. Asiemphytus fasciatus, immature stages, all photographs taken by S. Ibuki in Nakagawa in 2015.—1,
2, Small group of eggs (arrowed) deposited in the leaf tissue of Cornus controversa, July 23; 3, ﬁrst instar larvae (arrowed) on an infested leaf, July 26 (probably hatched on July 25); 4, second instar larva, July 29; 5,probably third instar larva with a cast skin, July 31; 6, probably third instar larva, July 31; 7, probably fourth
instar larva, August 5; 8, last instar larva, Koisago, June 4; 9, last instar larva, Oyamada, June 26; 10, last
instar larva, Koisago, June 4; 11, mature larvae, August 8.

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Discussion
Life History
The ﬁeld observations and rearing records
given above indicate that Asiemphytus fasciatus
probably has three generations a year in Nakagawa Town. The occurrence of the larvae in June
(SI150604 and SI150609 in Fig. 12) implies that
their parent adults were active and oviposited in
May to early June, and these adults probably
belonged to the ﬁrst emergence for the year. The
second emergence of the adults occurred in July(dark blue in Fig. 12) and the third emergence inlate August to September (offspring of SI150609
in Fig. 12). The larvae of the last generation
matured in October (SI150920) and most probably went into prolonged diapause until the next
spring.
In the case where one full generation wasobserved in July to August (offspring of
SI150609, Fig. 12, all unfertilized male eggs),
the incubation period was only ﬁve days, the larval feeding period was about 14 days and the
prepupal plus pupal period was 18 to 20 days
(one exceptional case 42 days). This is probably
the shortest developing period because the season was during the warmest part of summer. In
other cases observed in June to July (SI150604,

SI150609, Fig. 12), the larval feeding period was
longer than 23 days at least in one individual andthe prepupal plus pupal period ranged from 18 to
27 days.
Tomizawa (1934) studied the life history ofAsiemphytus deutziae (Takeuchi, 1929), whichfeeds on Deutzia crenata. This species has twogenerations a year in Tokyo, with the adult emergences in mid-April and mid-September. The
female deposits an average of three or four eggs
per leaf. The incubation period is about 10 days.
On maturing, the larva enters a dead stem andthere pupates after a long prepupal stage. Asiemphytus deutziae differs from A. fasciatus in having only two generations a year (no summer generation) but they both utilize dead stems orwood, not soil, for diapausing and pupating sites.
The use of dead stems or wood for spending thedormant stage is known only for species of
Selandriinae and some Allantinae and Blennocampinae (Okutani, 1957).
Host Plant
Host plants of the species of Asiemphytus Malaise, 1947, were known for only three Japanese
species, A. albilabris (Takeuchi, 1929), A. deutziae and A. vexator (Smith, 1874), and all areassociated with Deutzia crenata (Hydrangeaceae)

Fig. 12. Rearing records of Asiemphytus fasciatus in Nakagawa from June to October, 2015. Each individual in
the four groups is shown separately, except for the offspring of SI150609 (15 individuals, which grew almost
simultaneously until maturation). a: Matured and entered rotten wood but died or did not emerge before October 25. b: Combined data of 15 individuals. See text for more details and explanation.

Biology of Asiemphytus fasciatus(Takeuchi, 1929; Okutani, 1967). Our discoveryof the association of A. fasciatus with Cornus
controversa is the ﬁrst host plant record of Cornus and Cornaceae for an Asiemphytus species.
The families Hydrangeaceae and Cornaceae bothbelong to the order Cornales and are phylogenetically fairly closely related (Xiang et al., 2011).
Asiemphytus is represented by 10 species distributed in Primorsky Kray, Japan, China, andVietnam (Taeger et al., 2010). Malaise (1947)
proposed the genus for the East Asian species
originally described in Macremphytus MacGillivray, 1908, which currently contains ﬁve North
American and one Chinese species (Taeger et al.,2010). These two genera have much in common,and it is interesting that four species of Macremphytus from North America, M. lovetti MacGillivray, 1923, M. semicornis (Say, 1836), M. tarsatus (Say, 1836) and M. testaceus (Norton, 1861),
feed on Cornus, which is the only plant genus
recorded as hosts of Macremphytus (Smith,1979). A close one-to-one host plant relationshipbetween tenthredinid sawﬂy species groups/genera and plant genera/families certainly exists.
Examples include a tenthredinine genus Conaspidia Konow, 1898 and Araliaceae (the sikkimensis group and Aralia and the scutellaris group
and Kalopanax) (Shinohara and Ibuki, 2011) andan allantine genus Emphytopsis Wei and Nie,
1998 and Stewartia (Theaceae) (Shinohara et al.,2014). The relationship of Macremphytus with
Cornus is another example. The association of
Asiemphytus both with Deutzia and Cornus
appears irregular and it may suggest a heterogeneous nature of the genus itself. Accumulation offurther data on the host plants and clariﬁcation ofphylogenetic relationships of the species ofAsiemphytus and Macremphytus are needed forunderstanding the evolution of these sawﬂies
which may possibly be connected with host preference shift.
In Japan, another allantine sawﬂy, Togashia
horii (Togashi, 1962), is known to feed on Cornus controversa. It is a much larger species,
whose eggs are deposited in large groups (lines)
along the lateral veins on a leaf (Togashi, 1976).

53

Togashiʼs ﬁgure 2 shows long lines of eggs
deposited along (on both lateral sides of) ninelateral veins on one leaf (thus 18 lines of eggs),
suggesting that a great number of larvae will feed
gregariously. In A. fasciatus, the eggs are laid ina small group, not lined up along the veins, andthe larvae are solitary (Figs. 1–3).
Acknowledgements
We thank David R. Smith, United States
Department of Agriculture, Washington, D. C.,for his careful review of the manuscript. This
study was partly supported by JSPS KAKENHI
Grant No. 25440223.
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