Bull. Natl. Mus. Nat. Sci., Ser. A, 49(4), pp. 155–159, November 22, 2023
DOI: 10.50826/bnmnszool.49.4_155

Immature Stages and Life History of a Hazel Leaf-rolling Sawﬂy,Pamphilius benesi (Hymenoptera, Pamphiliidae)
Akihiko Shinohara1 and Yu Kato2
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
c/o Kanagawa Prefectural Museum of Natural History,Iriuda 499, Odawara, Kanagawa 250–0031, Japan
E-mail: yukato.crf@gmail.com(Received 22 August 2023; accepted 20 September 2023)

Abstract Based on the material obtained in Kôshû City, Yamanashi Prefecture, Honshu, observations on the oviposition and results of the rearing experiments of Pamphilius benesi Shinohara,
1985, are presented, the life history of this sawﬂy is outlined, and the immature stages and the larval leaf-rolls are brieﬂy described and illustrated.
Key words: Symphyta, Corylus sieboldiana var. sieboldiana, Betulaceae.

Introduction
Pamphilius benesi Shinohara, 1985, is a leafrolling sawﬂy occurring in Japan (Hokkaido,Honshu, Shikoku, Kyushu) and South Korea(Shinohara, 1985, 2001; Shinohara et al., 2022).
Shinohara and Hara (1997) reported on the hostplant and larvae of this species for the ﬁrst time
based on the observations in Hokkaido and Shinohara and Hara (2005) gave a concise accountof the larvae and life history with color photographs. These are the only references to the hostplant, larvae and life history of P. benesi. The larvae of this sawﬂy are gregarious leaf-rollers on
Corylus sieboldiana Blume var. sieboldiana(Betulaceae).
At the end of May 2022, Kato found a femaleof P. benesi ovipositing on a leaf of C. sieboldiana var. sieboldiana in Kôshû City, Yamanashi
Prefecture, Honshu, and made observations on its
oviposition behavior. He also reared the eggs andthe larvae until their last feeding instar. Here we
report on these observations, which will add© 2023 National Museum of Nature and Sciencemuch more details to the currently available,
rather fragmentary information based only on
Hokkaido material (Shinohara and Hara, 1997,2005).
Materials and Methods
Rearings were made by Kato in YokohamaCity, Kanagawa Prefecture. The temperature andday length of the rearing room were not rigidlycontrolled. For morphological terminology, wegenerally follow Viitasaari (2002). Photographs
were taken with Canon EOS 8000D or Olympus
Stylus TG–4 Tough by Kato. The digital images
were processed and arranged with Adobe Photoshop Elements 15 software.
Results and Discussion
Field observations and rearing records. OnMay 28, 2022, Kato discovered a female of Pamphilius benesi ovipositing on a leaf of Corylus
sieboldiana var. sieboldiana in Enzan-kamihagihara (35.710°N, 138.830°E, 1,370 m alt.), KôshûCity, Yamanashi Prefecture. The female was on

156A. Shinohara and Y. KatoFig. 1. Pamphilius benesi. —— A, Ovipositing female on leaf of Corylus sieboldiana, Group Ab, May 29; B,
three eggs, Group Aa, May 29; C, remains of six eggshells, Group Aa and Ab, and leaf-roll made by young
larvae, June 6; D, larvae inside the same leaf-roll, June 6; E, ovipositing female on leaf of C. sieboldiana,Group B, May 29; F, leaf with ﬁve eggs, Group B, May 29; G, eggs of Group B, possible marks of sticky substance arrowed, May 29. All photographed by Kato.

the underside of a leaf on a branch about 2
meters above the ground in a tree 4 to 5 meters
high. The female had already deposited threeeggs (Group Aa) which formed a line along themain vein in the basal part of the leaf (Fig. 1B).

The female was captured alive. There were noother eggs on the leaves around.
On May 29, in a container with the host plant,
the female deposited ﬁve eggs in a line along themain vein of a leaf (Group B, Fig. 1F, G). Then,Biology of Pamphilius benesi

157

Fig. 2. Pamphilius benesi. —— A, Eggs, remains of eggshell and newly hatched larva beginning to make leafroll, Group B, June 5; B, C, early instar larva, June 7; D, E, middle instar larva, June 14; F, late instar larva,June 23; G, H, J, late instar larva, June 21; I, late instar larva, June 28. All photographed by Kato.

the female moved to the leaf with Group Aa anddeposited three additional eggs (Group Ab) making a line along the main vein apical to Group Aa(Fig. 1A). Therefore, on this leaf, there are six
eggs apparently forming one linear egg group

along the main vein (Fig. 1C), which is actually acomposite of Group Aa (basal position, depositedon May 28) and Group Ab (apical position,deposited on May 29).
Three eggs of Group Aa hatched on June 5,

158

A. Shinohara and Y. Katoand the larvae made a leaf roll together. Threeeggs of Group Ab hatched on June 6. Two larvae
went to the leaf roll made by Group Aa andstayed in this roll together, while another one
went to the leaf margin and died soon without
making a leaf roll. One egg of Group B hatchedon June 5, four eggs hatched on June 6, and they
made a leaf roll together. The two groups of
totally ten larvae were reared in the same container and regrouped into three segregates of two
to four individuals soon. During June 7 to 11,
four young larvae died. During June 12 to 17,
three middle-instar larvae died (two of themﬁxed in ethanol) and the remaining three lateinstar larvae died thereafter, the last one ﬁxed inethanol on June 29.
Oviposition (Fig. 1A, E). The eggs weredeposited in a group of ﬁve to ten (Shinohara andHara, 1997; present work) along the main veinand lateral vein (Shinohara and Hara, 1997,2005) or forming a line closely beside the mainvein (present work, Fig. 1C, F) on the undersurface of the basal part of the leaf. The female
deposited eggs always directing her head towards
apex of the leaf (Fig. 1A, E). During the oviposition, no distinct behavior of painting or covering
the eggs by sticky substance was observed, butthe deposited eggs may have been covered withsuch substance, which apparently remained also
on the leaf surface nearby (Fig. 1G, arrowed).
Egg (Fig. 1B, G). Length about 2.5 mm, longoval, yellowish white. The incubation period was
six or seven days.
Larva. Early instar (Figs. 1D, 2A–C): Length
about 4 mm, head blackish brown, antenna
creamy white; trunk creamy white. Middle instar(Fig. 2D, E): Length 10–13 mm; head capsule
black; mouth parts whitish, partly blackish;
antenna creamy white; trunk semi-translucent,whitish; thoracic segment 1, lateral parts of trunkand subanal appendage creamy white, most of
dorsal prothoracic shield and cervical sclerite
black; suranal hook blackish. Last instar (Fig.
2F–J): Length about 15 mm (up to 18 mm, Shinohara and Hara, 2005); similar to middle instar;
blackish mark on dorsal prothoracic shield (Fig.

2G, J) often reduced or missing (Fig. 2F, I).
Larval leaf-roll (Fig. 1C). The larval leaf-roll
was made always on the underside of the leaf. It
was a simple leaf-roll and normal for the genus,
with both ends open and no frass kept inside. Allthe larvae from the same egg group lived
together in the same leaf-roll.
Host plant. Betulaceae: Corylus sieboldiana
Blume var. sieboldiana (Shinohara and Hara,1997; present work).
General life history. Pamphilius benesi isdoubtless univoltine as in other Pamphilius species. The adults occur mainly in late April toJune on mountains of Honshu, Shikoku andKyushu and in June in Hokkaido (Shinohara,1985, 1988, 2001; Shinohara and Hara, 1997).
The female lays eggs in a line along the main orlateral vein (ﬁg. 1A in Shinohara and Hara, 1997;
Fig. 1B, C, F, G) and the hatched larvae make asimple leaf-roll, in which they stay together. Theoviposition and the leaf-roll are always on theunderside of the leaf. The egg period is six orseven days. The larval period is not deﬁnitely
known, but one larva lived for 23 or 24 days in
our observation (the egg hatched on June 5 or 6
and the larva was ﬁxed in ethanol on June 29).
Shinohara and Hara (1997) noted that the individuals caught as young larvae spent up to 24
days until maturation. Because our larva mentioned above was apparently close to maturity
when ﬁxed on June 29, we estimate the wholelarval period to be 25 or 26 days.
Comparison with related species. Pamphilius
benesi is the only known species of Pamphiliidae
feeding on Corylus in Japan. It is one of the four
species of Pamphilius associated with Corylus inthe world. The European P. fumipennis (Curtis,1931) (also on Alnus) and P. marginatus (Serville, 1823) (also on Carpinus) and the NorthAmerican P. middlekauﬃ Shinohara and Smith,1983 (also on Cornus) are the other three species. Unlike P. benesi, these three species are solitary leaf-rollers (Stritt, 1935, 1937; Middlekauﬀ,1964).
Among the Japanese Pamphilius species, P.
alnicola Ermolenko, 1973, has much in common

Biology of Pamphilius benesi

with P. benesi in adult morphology, COI andNaK sequences, oviposition method and larval
gregariousness (Shinohara and Hara, 1993; Shinohara et al., 2022). The larvae of P. alnicola aregregarious leaf-rollers on Alnus hirsuta Turcz.
(Betulaceae) (Shinohara and Hara, 1993).
Besides the diﬀerence in host plants, the larvaeof the two species may be separated by the colorof the terminal abdominal segment; P. alnicola
has black spots on the segment both dorsally andventrally (Shinohara and Hara, 1993, 2005),
whereas P. benesi has no black spots on the segment (Fig. 2A–E, H–J).
Acknowledgements
We thank Hideho Hara (Bibai) for his careful
review of the manuscript.
References
Middlekauﬀ, W. W. 1964. The North American sawﬂiesof the genus Pamphilius (Hymenoptera: Pamphiliidae).
University of California Publications in Entomology,
Berkeley 38: 1–84.
Shinohara, A. 1985. Web-spinning sawﬂies of the sylvaticus group of Pamphilius (Hymenoptera, Pamphiliidae).
Systematic Entomology 10: 323–351.
Shinohara, A. 1988. The group of Pamphilius sylvaticus(Hymenoptera, Pamphiliidae)—Five new species and159

additional records from the Far East—. Kontyû 56:
307–320.
Shinohara, A. 2001. The group of Pamphilius sylvaticus(Hymenoptera, Pamphiliidae): Two new species, newcollection records, and a key to Palearctic species. Japanese Journal of Systematic Entomology 7: 99–116.
Shinohara, A. and H. Hara 1993. Larvae of Pamphilius
alnicola (Hymenoptera, Pamphiliidae), gregarious leafrollers on Alnus hirsuta. Japanese Journal of Entomology 61: 546.
Shinohara, A. and H. Hara 1997. Occurrence of Pamphilius benesi (Hymenoptera, Pamphiliidae) in Hokkaido, Japan, and notes on its gregarious leaf-rolling
larvae on Corylus sieboldiana. Japanese Journal ofEntomology 65: 851–852.
Shinohara, A. and H. Hara 2005. Pamphiliidae. In Ishiwata, S. et al.: Insect Larvae of Japan, pp. 272–276.
Gakken, Tokyo (in Japanese).
Shinohara, A., K. Kramp and A. Taeger 2022. The Pamphiliinae of the Russian Far East and Korea (Hymenoptera, Pamphiliidae). Zootaxa 5167: 1–251.
Stritt, W. 1935. Beiträge zur Biologie der BlattwespenGattung Pamphilius Latr. (Hym., Tenthr.). Verhandlungen des Naturwissenschaftlichen Vereins in Karlsruhe
31: 137–153.
Stritt, W. 1937. Die Larve des Pamphilius marginatus
Lep. (Hym., Tenthr.). Mitteilungen der Deutschen
Entomologischen Gesellschaft e.V., Berlin 8(2): 20–22.
Viitasaari, M. 2002. The suborder Symphyta of theHymenoptera. In Viitasaari, M. (ed.): Sawﬂies 1(Hymenoptera, Symphyta), pp. 11–174. Tremex Press,Helsinki.