Research Article |
Corresponding author: Hongbin Liang ( lianghb@ioz.ac.cn ) Academic editor: Michael Schmitt
© 2018 Kaiqin Li, Hongbin Liang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Li K, Liang H (2018) A comparative study of external female genitalia (including the 8 th and 9 th abdominal segments) in the family Megalopodidae and other related families of Chrysomeloidea. ZooKeys 762: 69-104. https://doi.org/10.3897/zookeys.762.22163
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The external female genitalia of 29 species belonging to three genera of Megalopodidae and 80 species belonging to 61 genera of another four families in Chrysomeloidea were studied. The external female genitalia within the superfamily Chrysomeloidea can be divided into a cerambycid type and a chrysomelid type. The comparative study of external female genitalia shows Megalopodidae is more closely related to the family Cerambycidae than to the family Chrysomelidaes.l. Among five subfamilies of Cerambycidae we studied, the subfamily Lamiinae is most closely allied to Megalopodidae. An evolutionary path is proposed for the spiculum gastrale in Chrysomeloidea: the characteristic state of the spiculum gastrale without a joint is primary, and that with a joint is secondary. The family Orsodacnidae has probably evolved in isolation from the early chrysomelids, due to their shared external female genitalia (cerambycid type). In the family Chrysomelidae, the structure of external female genitalia and ovipositing behavior show that the subfamily Synetinae is closer to the Camptosomata than the subfamily Eumolpinae. In general, the shape of the terminal ovipositor is palp-like in the Chrysomeloidea. Terminal ovipositors are generally palp-shaped in Chrysomeloidea except for those that are lamellate in the genus Callispa and the subfamily Cassidinae who produce egg-sheaths.
Chrysomeloidea , female genitalia, Megalopodidae , morphology, 8th abdominal segment
Adults of the family Megalopodidae commonly feed on the juices in stems and leaf tissues of plants in the families of Rosaceae, Oleaceae, Salicaceae, and Celastraceae, or consume the pollen of the Araucaria species (
Male and female genitalia are among the most important identification characteristics in the Megalopodidae and receive much attention from taxonomists.
Research on external female genitalia in the Megalopodidae is rare. There were only a few descriptions of male or female genitalia for this family when new species were described or revisions were made (
All measurements were made with the aid of an ocular micrometer in the Nikon SMZ1500 stereoscopic microscope. Dry specimens were soaked in boiled water for 1–2 hours. For larger specimens the lateral margin of the abdomen was opened at its apex and the genitalia were pulled out of the abdomen with fine forceps. For smaller specimens the whole abdomen was removed from the body. The genitalia and/or whole abdomen were soaked in a warm solution of 10% KOH for 10–20 minutes as a pretreatment. The treatment time depended upon the degree of sclerotization found in different species. After pretreatment these organs were washed in water several times. Genitalia were then detached and some were dyed with Chlorazol Black E to stain membranous tissue a blue color. They were then transferred to glycerin for observation, photography, and preservation.
Photographs of female genitalia were taken using a Nikon SMZ-1500 stereoscopic dissecting microscope fitted with a Cannon 450D digital camera. Photographs of habitus were captured by a Cannon Macro 100 mm lens fitted to the Cannon 450D camera. For each final image, several photographs were taken at different focal planes, combined with Helicon Focus software to obtain one synthesized photograph, and finally edited with Adobe Photoshop software.
Morphological terminology for the female genitalia of the Megalopodidae follows
Outside the ovipositor of Nupserha bicolor Thomson (Cerambycidae) there is a membranous bag-like capsule known as the capsular sheath (
Twenty-nine species belonging to three genera of Megalopodidae (including two subfamilies Megalopodinae and Zeugophorinae) were examined in this study (Table
Family | Subfamily | Species | Locality |
---|---|---|---|
Megalopodidae | Megalopodinae | Poecilomorpha cyanipennis (Kraatz) | Zhejiang (Hangzhou) |
Poecilomorpha discolineata (Pic) | Yunnan | ||
Poecilomorpha downesi (Baly) | Sichuan | ||
Poecilomorpha laosensis (Pic) | Indochina | ||
Poecilomorpha maculata (Pic) | Guangxi, Yunnan; Vietnam | ||
Poecilomorpha mouhoti (Baly) | Yunnan | ||
Poecilomorpha pretiosa Reineck | Guangxi, Zhejiang | ||
Temnaspis bonneuili Pic | Northeast of China | ||
Temnaspis femorata (Gressitt) | Fujian, Guangxi | ||
Temnaspis fraxini (Komiya) | Taiwan | ||
Temnaspis humeralis Jacoby | Hubei, Chongqing | ||
Temnaspis nigriceps Baly | Yunnan | ||
Temnaspis japonica Baly | Japan | ||
Temnaspis nankinea (Pic) | Henan | ||
Temnaspis omeiensis (Gressitt) | Sichuan | ||
Temnaspis pulchra Baly | Jiangxi | ||
Temnaspis septemmaculata (Hope) | Yunnan | ||
Temnaspis syringa Li and Liang | Beijing | ||
Temnaspis vitalisi (Pic) | Yunnan | ||
Zeugophorinae | Zeugophora (Pedrillia) annulata Baly | Heilongjiang | |
Zeugophora (Pedrillia) bicolor Kraatz | Liaoning | ||
Zeugophora (Pedrillia) longicornis Westwood | Yunnan | ||
Zeugophora (Pedrillia) dimorpha (Gressitt) | Hunan | ||
Zeugophora (Pedrillia) yunnanica Chen and Pu | Yunnan | ||
Zeugophora ancora Reitter | Ningxia | ||
Zeugophora cribrata Chen | Qinghai | ||
Megalopodidae | Zeugophorinae | Zeugophora cyanea Chen | Qinghai |
Zeugophora scutellaris Suffrian | Heilongjiang | ||
Zeugophora turneri Power | Beijing | ||
Cerambycidae | Prioninae | Aegolipton marginalis (Fabricius) | China |
Megopis (Aegosoma) sinica sinica (White) | China | ||
Spondylidinae | Asemum amurense Kraatz | China | |
Spondylis buprestoides (Linnaeus) | China | ||
Lepturinae | Leptura annularis annularis Fabricius | Heilongjiang | |
Leptura sp. | Guangxi | ||
Gaurotes virginea aemula (Mannerheim) | China | ||
Cerambycinae | Anoplistes halodendri (Pallas) | Inner Mongolia | |
Aromia bungii (Faldermann) | China | ||
Purpuricenus temminckii (Guérin-Méneville) | China | ||
Lamiinae | Bacchisa comata (Gahan) | Hainan | |
Eodorcadion brandti (Gebler) | China | ||
Glenea centroguttata Fairmaire | Xizang | ||
Glenea pulchra Aurivillius | China | ||
Monochamus alternatus alternatus Hope | Hubei | ||
Moechotypa diphysis (Pascoe) | China | ||
Oberea formosana Pic | China | ||
Paraglenea fortunei (Saundeas) | China | ||
Phytoecia rufiventris Gautier des Cottes | China | ||
Thyestilla gebleri (Faldermann) | China | ||
Orsodacnidae | Orsodacninae | Orsodacne cerasi (Linnaeus) | Yunnan |
Chrysomelidae | Sagrinae | Sagra (Sagra) femorata Drury | China |
Sagra (Sagrinola) mouhoti Baly | Yunnan | ||
Bruchinae | Callosobruchus chinensis (Linnaeus) | China | |
Donaciinae | Donacia clavipes clavipes Fabricius | Beijing | |
Donacia longicornis Jacoby | China | ||
Donacia provostii Fairmaire | Hebei | ||
Donacia vulgaris vulgaris Zschach | Hebei | ||
Macroplea mutica (Fabricius) | Mongolia | ||
Plateumaris weisei (Duvivier) | China | ||
Plateumaris sericea (Linnaeus) | China | ||
Plateumaris socia (Chen) | Northeast of China | ||
Sominella longicornis (Jacobson) | China | ||
Sominella macrocnemia (Fischer Von Waldheim) | Heilongjiang | ||
Criocerinae | Crioceris quatuordecimpunctata (Scopoli) | China | |
Lema coromandeliana (Fabricius) | Yunnan | ||
Lema nigricollis Jacoby | Yunnan | ||
Lilioceris cheni Gressitt & Kimoto | Guangxi | ||
Chrysomelidae | Criocerinae | Lilioceris consentanea Lacordaire | China |
Lilioceris gibba (Baly) | Jiangxi, Fujian | ||
Oulema oryzae (Kuwayama) | Heilongjiang | ||
Eumolpinae | Abiromorphus anceyi Pic | Hebei | |
Basilepta sp. | China | ||
Chrysochus chinensis Baly | Jilin, Heilongjiang | ||
Colasposoma dauricum Mannerheim | Yunnan | ||
Platycorynus parryi Baly | Guangxi | ||
Platycorynus sp. | Yunnan | ||
Lamprosomatinae | Oomorphoides yaosanicus (Chen) | Fujian | |
Cryptocephalinae | Cryptocephalus altaicus Harold | Inner Mongolia | |
Cryptocephalus limbellus semenovi Weise | Inner Mongolia | ||
Aspidolopha bisignata Pic | Jilin, Yunnan | ||
Clytra laeviuscula Ratzeburg | Jilin | ||
Physosmaragdina nigrifrons (Hope) | Guangxi | ||
Chlamisus stercoralis (Jacoby) | Guangxi | ||
Synetinae | Syneta adamsi Baly | Shanxi | |
Chrysomelinae | Ambrostoma quadriimpressum (Motschulsky) | Heilongjiang | |
Agasta formosa Hope | Yunnan | ||
Chrysolina aurichalcea (Mannerheim) | Guangxi | ||
Chrysomela populi Linnaeus | Harbin, Jilin | ||
Gastrophysa atrocyanea (Motschulsky) | Sichuan | ||
Phratora bicolor Gressitt & Kimoto | Sichuan | ||
Galerucinae | Gallerucida sp. | Yunnan | |
Medythia nigrobilineata (Motschulsky) | Heilongjiang | ||
Mimastra limbata Baly | Yunnan | ||
Morphosphaera cavaleriei Laboissière | China | ||
Oides tarsatus (Baly) | Guangxi | ||
Paleosephraria sp. | Yunnan | ||
Alticinae | Altica viridicyanea (Baly) | Beijing | |
Podontia affinis (Gröndal) | Yunnan | ||
Podontia dalmani Baly | Yunnan | ||
Podontia lutea (Olivier) | Guangxi | ||
Hemipyxis sp. | China | ||
Cassidinae | Octodonta nipae (Maulik) | Hainan | |
Lasiochila cylindrica (Hope) | Yunnan | ||
Dactylispa sp. | Yunnan | ||
Callispa brettinghami Baly | Yunnan | ||
Callispa fortunei Baly | Yunnan | ||
Callispa nigricollis Chen & Yu | Yunnan | ||
Leptispa longipennis (Gestro) | China | ||
Basiprionota bisignata (Boheman) | Guangxi |
The 8th and 9th abdominal segments (Figs
1 Female internal reproductive system of Temnaspis nankinea (Pic), ventral view 2 8th and 9th abdominal segment of T. nankinea, ventral view 3 Muscles of abdominal segment of T. nankinea, ventral view; Abbreviations: genital chamber (Gc); genital pocket (GetP); muscle (Mus); ovary (Ova); spermathecal gland (SptGl); spiculum gastrale (SplG); sternite 8 (8 Ste); scale line = 2.0 mm (Figs
The lateral side of the tergite and sternite is connected tightly by a membrane that extends from the apex of the abdominal segment to form a flattened tube that is slightly curved on its ventral side (Figs
7–8. 8th abdominal segment of Temnaspis nankinea (Pic). 7 ventral view 8 lateral view 9–10 Part of 8th abdominal segment of Poecilomorpha discolineata (Pic) 9 ventral view 10 lateral view 10–12 8th abdominal segment of Zeugophora (Pedrillia) bicolor Kraatz 11 ventral view 12 lateral view; Abbreviations: sclerotized plate (SP); scale line = 1.0 mm.
The 9th abdominal segment is long and all of its components are wrapped in a genital pocket. The ovipositor is a long scissor-like, strongly sclerotized, basal half portion that is broad and flattened. Its two oblique palpi are separated on the posterior portion. Their apices are generally close to each other. The outer margin of the ovipositor is slightly flattened (Figs
13–16. Ovipositor 13 Temnaspis fraxini (Komiya), ventral view 14 Poecilomorpha cyanipennis (Kraatz), ventral view 15Zeugophora (Pedrillia) dimorpha (Gressitt), ventral view 16 Zeugophora cyanea Chen, ventral view 17 the connecting of ovipositor and 8th abdominal segment, Zeugophora (Pedrillia) bicolor Kraatz, ventral view; Abbreviations: membrane (Mem); ovipositor (Ovi); 8th abdominal segment (8 AS); scale line = 0.5 mm.
The main muscles of the 8th abdominal segment in Temnaspis nankinea (Pic) were examined. It was found that, on the genital plate, there is a large paired bundle of fan-shaped muscles between the median and the lateral apodeme of the anterior margin of sternite 8 (Figs
The structure and morphology of female genitalia of the subfamilies Zeugophorinae and Megalopodinae are very similar. However, their body sizes and external morphologies differ significantly. The genital pocket is approximately cylindrical, its anterior end is narrow, and its posterior portion is flat and generally broadly extended beyond the genital plate. Apical margins of tergite 8 and sternite 8 are nearly equal in length, and rarely contained a row of setae. The ventral apical margin is slightly sclerotized, and the opening of the genital pocket does not close tightly. The curved portion of the flattened tube is located far from the posterior opening. The coxite generally does not exceed the curved portion. The shape of the genital plate is different from that of the Megalopodinae. The genital plate in the Zeugophorinae is cordate in some species (Figs
In the majority of members of the family Cerambycidae the tergite and sternite of the 8th abdominal segment are combined to form a flattened segment (Fig.
18 Part of internal reproductive system and ovipositor of Aromia bungii (Faldermann), ventral view 19–20 ovipositor of Leptura annularis annularis Fabricius 19 dorsal view 20 ventral view 21 ovipositor of Glenea pulchra Aurivillius. Abbreviations: genital pocket (GetP); ovipositor (Ovi); spiculum gastrale (SplG); 8th abdominal segment (8 AS); scale line = 1.0 mm (Figs
In general, the genital pocket is cylindrical in shape, but variable among different species. The variation of genital pocket is correlated with the change of the 8th abdominal segment. The spiculum gastrale is thin and long, almost four times the length of sternite 8 and it also has a rod-like or slightly thick apex (Fig.
The 9th abdominal segment is generally elongated and membranous (Fig.
1. Prioninae
The 8th abdominal segment in the subfamily Prioninae (genus Aegosoma) is exposed to the outside with the posterior extending into a cone-like shape. The genital pocket folds inward from the apex of the 8th abdominal segment. The apical portion of the genital pocket is narrow and its membrane is rather thick and tightly wrapped in the center forming a thin pipe. The apex of the spiculum gastrale is slightly thickened and is connected to the sternite by a joint. The components of the ovipositor are sectioned clearly with an outward apex. The coxite is slightly swollen. The stylus is small and located on the lateral side of the coxite.
2. Spondylidinae
The tergite of the 8th abdominal segment in the subfamily Spondylidinae (genus Spondylis) is sclerotized and the ventrolateral side of the tergite is folded. Most portions of the sternite are membranous and a sclerite is found on either side. The apical margin of the 8th abdominal segment is folded inward to form a genital pocket. The spiculum gastrale is located between the sclerites of the sternite centroapical margin, which connects to the sternite without a joint. The components of the ovipositor are complete and easily viewed. The coxite is slightly swollen. The stylus is located on the lateral side of the coxite.
3. Cerambycinae
In the genus Aromia, the length of the 8th abdominal segment is longer than its width (Fig.
4. Lepturinae
In the genus Leptura, the length of the 8th abdominal segment is longer than its width and its tergite is connected to the sternite via a membrane that forms a flattened segment. The tergite and the sternite are slightly sclerotized and the apical margin of the 8th abdominal segment folds inward to form a genital pocket. There is a joint between the spiculum gastrale and the sternite. The ovipositor is rather long, its posterior portion extends outward, making the components of the ovipositor clearly visible. The stylus is located on the apex of the swollen coxite (Figs
5. Lamiinae
Lamiinae is a subfamily that includes a variety of taxa. We observed the genitalia of the following genera: Monochamus, Oberea, Glenea (Fig.
Morphological variation of female genitalia in the Cerambycidae is rather minimal compared to the Chrysomelidae. Females in the Cerambycidae usually lay their eggs in tree bark cracks, under tree bark or in soil (
Abdominal segment 8 is sub-quadrate. The tergite and sternite are weakly sclerotized and are connected via a membrane on lateral sides forming a flattened cylindrical segment. The central portion of the tergite is membranous while the central portion of the sternite has one weakly sclerotized sclerite without an apodeme (Fig.
Ovipositor and 8th abdominal segment of Orsodacne cerasi (Linnaeus) 28–29 ventral view 30 dorsal view; Abbreviations: coxite (Cox); genital pocket (GetP); median plate (MedP); paraproct (Par); baculus of proctiger (PrgB); spiculum gastrale (SplG); stylus (Sty); valvifer (Val); 8th abdominal segment (8 AS); scale line =0.5mm.
In this family, the inside of the 8th abdominal segment has no genital pocket. Sternite 8 is usually reduced and the spiculum gastrale has no joint. The length of the 9th abdominal segment is usually shorter than the width of its base, and there is less membrane compared to the Megalopodidae, Cerambycidae, and Orsodacnidae. Morphological of the ovipositor is variable and has all components although some portions are reduced or fused. The baculi of the ovipositor are poorly developed. This includes the early branched groups (the Sagrinae and the Eumolpinae) and the late appeared group Alticinae and Cassidinae.
1. Sagrinae
The genus Sagra has a well-developed sternite 8 and a moderate to long spiculum gastrale. The apex of the spiculum gastrale is slightly expanded and its ovipositor is short and thick. The proctiger is membranous with a sclerite on each side of the proctiger. The apex of the proctiger inserts into tergite 8. The paraproct is strongly sclerotized and thick, while its apex is connected to the valvifer, coxite, and stylus. There is a median plate between the valvifer on its ventral side. This is representative of primitive types in the Chrysomelidae (Figs
Ovipositor and 8th abdominal segment 31–32Sagra (Sagrinola) mouhoti Baly 31 dorsal view 32 ventral view 33–34 Lilioceris cheni Gressitt & Kimoto 33 dorsal view 34 ventral view; Abbreviations: coxite (Cox); paraproct (Par); proctiger (Prg); spiculum gastrale (SplG); stylus (Sty); sternite 8 (8 Ste); tergite 8 (8 Teg); valvifer (Val); Scale line = 1.0 mm.
2. Bruchinae
The 8th abdominal segment, associated with members of the genus Callosobruchus, is quadrate. The ventral side of the tergite is close to the proctiger. The central part of the tergite is membranous and its lateral side is sclerotized. The sternite is membranous. The tergite and sternite are connected to each other on the lateral side. The spiculum gastrale is short, about 1.5 times the length of the sternite, and lacks a broad apex. In Callosobruchus chinensis (Linnaeus) the spiculum gastrale extends forward turning backward at its base. The length of the 9th abdominal segment is almost equal to the length of the 8th abdominal segment. The proctiger is approximately triangular and membranous with sclerotized lateral parts. The base of the proctiger is connected to the paraproct. The ovipositor is small. The valvifer, coxite, and stylus lack clear boundaries.
3. Criocerinae
This subfamily is similar to the Sagrinae but the spiculum gastrale is relatively short (Figs
4. Donaciinae
Donaciinae is an aquatic subfamily. The 8th and 9th abdominal segments are slightly sclerotized. The spiculum gastrale of the 8th abdominal segment is rather long. The 9th abdominal segment is significantly long and membranous. The proctiger is usually long, triangular and its basolateral side is connected to the paraproct. The valvifer usually fuses with the coxite. The stylus is generally indistinct. The area of sensory setae is located on the surface of the tip of the coxite and may be interpreted as a stylus (Figs
35 Ovipositor and 8th abdominal segment of Donacia longicornis Jacoby 36–37 Plateumaris weisei (Duvivier) 36 tergite 8 37 sternite 8 38–39 ovipositor of Macroplea mutica (Fabricius) 38 dorsal view 39 ventral view; Abbreviations: coxite (Cox); ovipositor (Ovi); paraproct (Par); proctiger (Prg); valvifer (Val); 8th abdominal segment (8 AS); scale line = 1.0 mm.
5. Eumolpinae
The reproductive segment of this subfamily is distinctive in the Chrysomelidae. In the genera Platycornus, Colasposoma and Chrysochus the tergite and sternite of the 8th abdominal segments fuse laterally, forming a flattened cylinder. The lateral side of tergite 8 has a sclerotized area and sternite 8 is sclerotized (Figs
6. Lamprosomatinae
In the genus Oomorphoides, the lateral side of tergite 8 is sclerotized and sternite 8 is slightly sclerotized without a spiculum gastrale (Fig.
7. Cryptocephalinae
7.1. Cryptocephalini
In the genus Cryptocephalus the proctiger is membranous and the central portion of its apex is emarginated with the lateral side sclerotized with sharp protrusions. The paraproct is developed with most of this structure connected to the proctiger. The ventral portion of the paraproct is located on the lateral side of the 9th segment. The coxite is a wedge-shaped sclerite, extending from central region to the outside, which connects it with the valvifer. This valvifer connects to the paraproct. The inner side of the coxite protrudes backward while the outer part is an inclined plate with some setae. This inclined plate should be the stylus (Figs
7.2. Clytrini
In genus Aspidolopha, the ovipositor has all components but the stylus is tiny. The coxite and valvifer have clear boundaries while the paraproct is strongly sclerotized.
7.3. Fulcidacini
In the genus Chlamisus, sternite 8 is membranous and the vaginal palpi are robust with no stylus. Most portions of the boundaries between the valvifer and coxite are invisible, with just a small piece located inside being visible. The valvifer is very long.
8. Synetinae
The last visible tergite (pygidium) extends backward (Fig.
48–50 Syneta adamsi Baly 48 8th abdominal segment, ventral view 49 ovipositor, dorsal view 50 egg dimple of last abdominal sternite, ventral view 51–53 Ovipositor, ventral view 51 Physosmaragdina nigrifrons (Hope) 52 species of Cryptocephalinae53 Oomorphoides yaosanicus (Chen); Abbreviations: ovipositor (Ovi); sternite 8 (8 Ste); tergite 8 (8 Teg); scale line = 0.5 mm (Figs
9. Chrysomelinae
The central portion of tergite 8 is membranous, and it is sclerotized laterally. The sternite is normal or reduced. The whole subfamily, except in the genus Timarcha, has no spiculum gastrale. The central section of proctiger is membranous, sometimes reduced. The basolateral margin of the proctiger is connected to the paraproct. The ovipositor is short, robust, and palp-like, its components are fused and it may have a median plate. Sternite 8 in the genus Chrysomela is membranous. Its apical margin is sclerotized and centrally emarginated while the ovipositor is rod-like, weakly sclerotized with a rather thin base. The components of the ovipositor are fully fused together, with the stylus circle-shaped at the apex (Fig.
10. Galerucinae
While the morphology of the spiculum gastrale is variable (Figs
11. Alticinae
There is no obvious difference between the 8th and 9th abdominal segments in the subfamilies Alticinae and Galerucinae. Both subfamilies lack distinct paraproct. The coxite in the genus Podontia is cylindrical and has a small stylus (Figs
12. Cassidinae
In this subfamily the pygidium is tergite 8, and in most species, sternite 8 is reduced to an arc-shaped piece. The spiculum gastrale is usually short and broad, but it is missing in a few species. The ovipositor palpi are rather short, with robust and plate-like apices. The coxite, valvifer, and paraproct are generally fused together. The stylus is usually indistinct. The proctiger is membranous, both sides have rectangular sclerites, base connected with the paraproct.
12.1. Hispini
The genus Octodonta has no spiculum gastrale and its ovipositor palpi are robust and broad, with apices bearing setae. The paraproct is transverse at the base. Sternite 8 in genus Lasiochila is arc-shaped with a short broad spiculum gastrale. Its ovipositor palpi are rather long, but are separated from each other at their bases becoming close to each other at their apices. (Figs
60 8th abdominal sternite of Callispa brettinghami Baly 61 8th abdominal sternite of Callispa nigricollis Chen & Yu 62 ovipositor of Callispa nigricollis Chen & Yu 63 8th abdominal sternite of Lasiochila cylindrica (Hope) 64 ovipositor of Lasiochila cylindrica (Hope) 65 ovipositor of Basiprionota bisignata (Boheman); scale line = 0.5 mm (Figs
The central portion of sternite 8 in the genus Dactylispa is sclerotized and the spiculum gastrale is rather narrow. Ovipositor palpi are long with distinctly big, thick apices. The stylus is not distinct and the coxite and valvifer fuse. The paraproct is located at the base of the ovipositor.
In the genus Callispa, the proctiger is membranous and the anterior margin on the lateral side has a sclerite while the paraproct is reduced to a transverse sclerite at the base of the ovipositor. The ovipositor is plate-like and the stylus, coxite, and valvifer are fused without a clear boundary (Figs
12. 2. Cassidini
In the genus Basiprionota, both proctiger and paraproct structure is similar to that of the genus Callispa but the paraproct is located at the base of the ovipositor and is reduced to form an erect sclerite. All parts of the ovipositor fuse into a plate-like structure (Fig.
After examining the external genitalia of females in the Megalopodidae and comparing them to families in Chrysomeloidea, we interpret the following.
I. We suggest dividing the female external genitalia of superfamily Chrysomeloidea into cerambycid type and chrysomelid type. In general, adult females with long ovipositors and a spiculum gastrale insert their egg into deeper substrate (plant tissue or soil). In contrast, females with shorter ovipositors and a spiculum gastrale lay eggs on substrate surfaces or shallow sites (
The main characteristics and representative group in these two types are discussed below.
1. The cerambycid type
The Megalopodidae, most species of Cerambycidae and the Orsodacnidae belong to this type. The 8th abdominal segment usually develops a genital pocket and the spiculum gastrale is thin and long. Indeed, it is four times longer than the sternite and is connected to the sternite via a joint. The length of its 9th abdominal segment exceeds the width of the base. The ovipositor is generally long with well-developed baculi.
2. The chrysomelid type
All chrysomelids, excluding members of the Orsodacnidae and a few species in the Cerambycidae, belong to this type. The 8th abdominal segment has no genital pocket and the spiculum gastrale connects to the sternite without forming a joint. The sternite is up to four times the length of the spiculum gastrale. The length of the distinctive 9th abdominal segment is generally shorter than the width of its base. The components of the ovipositor are relatively short and its baculus is poorly developed or absent.
II.Megalopodidae is closely related to subfamily Lamiinae. The morphology of female genitalia in the family Megalopodidae (includes subfamilies Megalopodinae and Zeugophorinae) is significantly different from the chrysomelids. The female genitalia in this family belong to the cerambycid type. The distinctive characteristics are listed as follows: (1) sternite 8 has a strongly sclerotized apodeme, (2) the inner side of the 8th abdominal segment has a stiff genitalia pocket, (3) the spiculum gastrale is connected to the sternite by a joint, (4) the 9th abdominal segment has no proctiger, (5) the paraproct is rather short or absent, (6) the coxite is thin and long, (7) the stylus is much reduced. The family Cerambycidae includes many subfamilies but morphological variation among its subfamilies is rather low. The ovipositor of most species in the Cerambycidae belongs to the cerambycid type. After comparing the morphology of external female genitalia between the Megalopodidae and Cerambycidae we found that the Megalopodidae are most like the subfamily Lamiinae of Cerambycidae. Our research results are congruent with the research of
III. The evolution of the spiculum gastrale in the Chrysomeloidea. The spiculum gastrale is an apodeme projection extending from the anterior-central region of sternite 8. The muscles attached to the spiculum gastrale correlate the mode of oviposition (see I. Megalopodidae) (
The development of spiculum gastrale A sternite 8 B sternite 8 central with convex longitudinal ridge C, D, E sternite 8 central with convex longitudinal ridge and lateral sides seperated from sternite to form spiculum gastrale without joint F spiculum gastrale connected with sternite 8 with joint.
IV. The female genitalia in subfamily Eumolpinae is a typical representative of the primary type. In general, the female genitalia in Orsodacninae, Sagrinae, Timarcha (Chrysomelidae) and Eumolpinae are interpreted as primary, because in these taxa female genitalia retain all the basic sclerites: proctiger, paraproct, valvifer, coxite, stylus, median plate (without in Timarcha) (
V. Orsodacnidae
This is a controversial group. It was regarded previously as a subfamily in the Chrysomelidae.
Crowson (1955) thought that some morphological characteristics of the larvae of Orsodacne were similar to the Criocerinae, Donaciinae, Sagra, Clytra, and Eumolpinae. Cox (1981) also suggested that the Orsodacninae was closer to the Zeugophorinae and Donaciinae based on larva characteristics. There is no doubt that the Orsodacninae are closer to the Galerucinae. In our study, we found that the 9th abdominal segment of Orsodacne is very similar to the same structure in some genera (Colasposoma, Platycorynus and Chrysochus) placed in the Eumolpinae. They share the same following features: a long 9th abdominal segment, the ovipositor visibly retains all structures and has developed baculi. However, the 8th abdominal segment in these three genera differs from that in the genus Orsodacne. Based on our comparison of the external female genitalia in the Chrysomeloidea and observations by other researchers on the genus Orsodacne, we suggest that Orsodacne separated from the cerambycid lineage at an earlier period. It moved from bored stems of plants to leaf-eating in the early evolution of the ancestor of Chrysomeloidea, but it keeps some plesiomorphy. It was in the clade that became the earliest independent chrysomelid lineage. Chrysomelidae (include other chrysomelids) was in the clade that evolved later than Orsodacne. We agree that the Orsodacnidae was an independent family but a sister family of the Chrysomelidae and it was equal in status to the Megalopodidae and Cerambycidae (
VI. Synetinae
With a reduced sternite 8, the oviposition behavior in the Synetinae is very similar to the Camptosomata including the subfamily Cryptocephalinae (Cryptocephalini, Clytrini and Chlamisus). All of them place a protective layer outside their eggs. They hold each egg by their hind tarsi and keep turning in the egg dimple of the 7th abdominal segment when the egg is expelled from their bodies (Jiang 1983, Yu 1996). Their digestive tracts discharge evenly to cover each egg forming a protective layer and then the egg is kicked out of their bodies (Yu 1996, Jiang 1983). The protective layer is formed by the Kotpresse (German language, meaning fecal press), which is a special structure on the rectum (
The female genitalia of the Synetinae are different from the more common Chrysomelidae. The tergite 8 (pygidium) was exposed and backward, so one could see the exposed apices of the ovipositor from its ventral side. The coxite is triangular lacking a distinct stylus. But on the inclined plane outside the coxite there is a small protrusion that should be the stylus because the valvifer connects with the coxite and paraproct at the base. This structure is similar to the membrane of the ovipositor in the Camptosomata (especially in some species in the genera Cryptocephalus and Clytra). Both the Synetinae and Camptosomata have a well-developed proctiger and a broad, sclerotized paraproct. Based on similar oviposition structure and behaviors, we speculate that the Synetinae has the closest relationship to the Camptosomata in the Chrysomelidae. However, we cannot exclude the possibility of parallel or convergent evolution of oviposition behavior in both taxa.
VII. Based on comprehensive observations of the female genitalia of the Chrysomeloidea, it was found that the apices of the ovipositor are usually palp-like and backward except in the subfamily Cassidinae and in the genus Callispa of Hispini, which has a wide, plate-like ovipositor.
Female genitalia are diverse, complex, and very important for classification of the Chrysomeloidea. With a comparative analysis of the female genitalia we can reach a well-resolved classification system of this family. Egg-laying behavior and oviposition media cannot to be ignored when we explore the evolution of this huge taxon, but we still know very little about the reproductive biology of individual species. This research is particularly limited in Chinese lineages and future research is desperately needed to compare all the members of this lineage to resolve the systematics of the Chrysomeloidea.
The authors thank Professor Peiyu Yu (Institute of Zoology, Chinese Academy of Sciences, China) for her valuable help in our Megalopodidae study; Dr. Meiying Lin (Institute of Zoology, Chinese Academy of Sciences, China) for providing some specimens of Cerambycidae and identifying them; Professor Peter Bernhardt (Department of Biology, Saint Louis University, USA) and Mr. Michael Fizdale (Hampshire College, Massachusetts, USA) and Dr. Zongxin Ren (Kunming Institute of Botany, Chinese Academy of Sciences, China) for correcting English for an earlier draft. This work is supported by grants from the National Natural Science Foundation of China (Grant No. 31572235) and the National Special Fund on Basic Research of Science and Technology (2014FY110100).