中生代的虻类(昆虫纲)

MESOZOIC GADFLIES (INSECTA:DIPTERA)

记述山东莱阳上侏罗统莱阳组昆虫化石2新属2新种.分别隶属于Solvidae科和Rhagionidae科.这些虻类化石在我国中生代晚期地层中尚属首次发现,其中Solvidae科种类也是首次在世界中生代晚期地层中发现.文中对有关的古生态、昆虫与植物的关系进行了讨论.同时,对我国已记录的中生代的虻类化石在分类学中存在的问题提出了某些新的见解.

This study involves two new species and two new genera separately belonging to the families Solvidae and Rhagionidae within the suborder Brachycera of Diptera, which are discovered from the Upper Jurassic Laiyang Formation of Laiyang, Shandong, with a review on the known fossil gadflies from Mesozoic of China. The species Beipiaoplecia malleformis Lin, Mesosolva parva Hong and Prosolva huabeiensis Hong from Middle Jurassic of Liaoning, China may be placed in the Asilomorpha within Brachycera, with the question still left open in taxonomic positions at the familial level. All the type specimens described are now deposited in the Shandong Provincial Museum, Jinan. I.DESCRIPTION OF NEW GENERA AND NEW SPECIES Family Solvidae Archisolva gen. nov. Type species Archisolva cupressa gen. et sp. nov. Diagnosis Body median-sized. Head wider than long. Eyes separated from each other. Antennae longer than head, with the first segment distinctly longer than the second, the latter oval, the third (flagellum) rather long, containing 12 annulate segments. Thorax obtuse-quadrate, nearly as wide as head. Legs thin and long, with spurs indistinguishable. Posterior tarsi longer than tibiae, with the first tarsal segment obviously longer than the second. Wings narrow and long, with veins stout. C running to apex. Sc running about two-thirds the length of wing, and ending at C.R_1 running three-fourths the length of wing, also ending at C. Rs originating from R about one-third the length of wing. Cross vein m-m rather long, connected with fork of M_(1+2). Cell 1st m_2 long and exceedingly wider than cell m_(3+4) which is narrow long, and triangular. Abdomen cylindrical, 8-segmented, much longer than head and thorax combined. Comparison The present new genus is close to Solva Walker (=Xylomyia Mijere), but differs in the flagellum of antenna consiting of 12 annulate segments; the spurs invisible; R_1 distinctly long; Rs originating from R quite close to wing base; and the cell 1st m_2 extraordinarily wider than cell m_(3+4). Distribution Shandong; Late Jurassic. Archisolva cupressa gen. et sp. nov. (Pl. I. fig. 1; Text-figs. 1, 2) Description A single specimen (Holotype: L88811) in dorsal view showing body blackish brown. Head subtriangular, 1.4 times as wide as long. Eyes suboval, occupying most parts of head. Antennae 1.3 times as long as head, with the first segment oblong, twice as long as wide; the second wider than long, the third 3 times as long as the first and second united, with each annulate segment subquadrate, longer than wide at basal aprt but wider than long at terminal part; styles small and short. Thorax nearly as long as wide, almost wholly occupied by scutum but scutellum likely appearing in posterior part. Legs clothed with short, dense hairs. Tarsi with the first four segments brown and remainder of leg light yellowish brown in color. Posterior femora stouter but evidently shorter than tibiae. Tarsi 1.2 times as long as tibiae, with the basitarsi nearly as long as remainders combined, about two-thirds the length of tibiae. Wings lipochromous and hyaline, 2.9 times as long as wide. C stout and straight. Sc stout but light-colored. Both R and R_1 stout. Wing venation as shown in text-fig 2. Abdomen 1.6 times as long as head and thorax united, with the widest part lying in the third segment; the last one clearly light-colored. Ovipostor short, subtriangular, and light-colored. Length Body 14.2mm (3.7mm in width); head 2.0mm; antenna 2.9mm; thorax 3.2mm; abdomen 8.6mm; posterior leg 12.0mm; wing 11.0mm. Horizon and Locality Nanligezhuang Village, Laiyang; Upper Jurassic Laiyang Formation. Family Rhagionidae Scelorhagio gen. nov. Type species Scelorhagio mecomastigus gen. et sp. nov. Diagnosis Body small-sized. Head median in size, circular. Antennae 3-segmented, with the first and second segments much more transverse; the third large, subcircular, and armed with elongate, likely segmented style. Proboscis stout and long but soft. Thorax massive; scutum elevated. Legs thin and long, with basitarsi much longer than the second ones; posterior legs distinctly longer than anterior and middle ones. Wings narrow and long. C running to apex. Both Sc and R coalescing basally, and Sc ending at midwing at C; R_1 stout, running about two-thirds the length of wing, and ending at C. Rs originating from R about one-third the length of wing. Stem of Rs short, with branches rather long. R_3 obviously curved upward terminally. Fork of R_(4+5) somewhat before terminal point of R_1. Both R_4 and R_5 elongate, running close to each other; and curved downward. M with 4 branches. Cell lst m_2 narrow and long. Cross-vein m-m long and running oblique, coalescing with M_2. Both CuA and A_1 coalescing near hind margin of wing. Abdomen massive and short, 7-segmented. Ovipostor small, short, and straight backward. Comparison Scelorhagio gen. nov. bears an affinity to the Ptiolinites Kovalev, but may be distinguished from the latter by the rather elongate style of antenna, the long and thin legs, the upward curved R_3 at terminal, the narrow and long cell lst m_2, as well as the cross-vein m-m coalescing with M_2. On the other hand, although this new genus is similar to Jurabrachyceron Kovalev in wing venation, it is easy to separate them because in the feature of the third antennal segment, both genera have nothing in common. Distribution Shandong; Late Jurassic. Scelorhagio mecomastigus gen. et sp. nov. (Pl. I. fig. 2; Text-fig. 3) Description A single specimen (Holotype: L88812) in right lateral view, showing body brown in color. Head with a subtriangular region in middle, rather light-colored. Eyes ill-preserved, probably occupying the whole head, but with only a few facets visible. Antennae with the first and second segments identical in shape and width, each about 2.5 times as wide as long; the third almost as long as the first and second combined; style twice as long as that of the first, second and third united, and left one likely segmented. Proboscis barely shorter than head, stouter basally than apically, rather light-colored, only a little darker and light yellowish brown in color terminally. Thorax distinctly thicker than head and abdomen. Scutum curved arcuately; scutellum indistinguishable, not clothed with any bristles and hairs. Legs clothed with short, dense hairs showing light brown in color. Femora shorter than tibiae, the latter being shorter than tarsi; basitarsi nearly as long as remainders united, with the second as long as the third or fifth; the fourth evidently shorter than others. Claws long, with onyehia invisible. Wings achromatic and pellucid. Veins thin and faint except for C, Sc, R and R_1. Wing venation as shown in text-fig. 3. Abdomen almost as long as head and thorax combined, widest at base, and gradually narrowing terminally, with segment venter rather light-colored. Ovipostor small, thin, and cylindrical. Length Body 4.0mm (1.7mm in thickness); antenna (including style) 0.7mm; head 0.7mm; thorax 1.6mm; abdomen 2.4mm; posterior leg 4.1mm; wing 3.4mm. Horizon and Locality Nanligezhuang Village, Laiyang; Upper Jurassic Laiyang Formation. Ⅱ.DISCUSSION So far, few fossils assigned to the family Solvidae have already been recorded throughout the world. Archisolva cupressa sp. nov. is the first undoubted finding within this group in the Mesozoic era. As compared with the oldest and modern solvids, this new species shows certain primitive characters, such as the third antennal segment consisting of 12 annulate segments; R_1 running about three-fourths the length of wing; the lay of the fork of R close to the wing base, about one-third the length of wing; and the cell lst m_2 appearing much more widened. Archisolva cupressa might be of a forest insect, for the extant members of Solvidae live usually in woods. As the dominant Brachyphyllum obesum Heer coexists with this insect from the same location and the same horizon, a deduction may be derived that it is probably the host plant of Archisolva cupressa. Most snipe flies are common in woodland, especially near moist places, and usually found on foliage. Only a single kind of the Late Jurassic Equisetales recovered from the Laiyang Formation is regarded as a plant living in marshland near the shore of ancient Laiyang lake. Scelorhagio mecomastigus sp. nov. might have a close relation to this herb in bioecology. There are three species and three genera of gadflies from the Middle Jurassic of Liaoning, China, among which Beipiaoplecia malleformis Lin was originally placed in the family Eopleciidae within the suborder Nematocera (Lin, 1976). Hong (1983) agreed with Lin's opinion. However, Kovalev (1982) regarded this species as a gadfly and classified it in the Asilomorpha of Brachycera. The authors consider Kovalev's opinion as well-founded, because the antenna of B. malleformis shows a typical character of gadflies (Lin, 1976, pl. I, fig. 9). Hong (1983) described two species and two genera and assigned them to the family Solvidae, namely, Mesosolva parva Hong and Prosolva huabeiensis Hong. Based on the features of antenna (Hong, 1983, pl. 24, fig. 2; pl. 23, fig. 9), they should not be regarded as members of Solvidae; just like B. malleformis, they are quite similar to the Rhagionidae in antennal characters. Perhaps they belong to an unknown group at the familial level, if their wing venations were drawn correctly. Acoording to Hong (1982), Protabanus chaoyangensis Hong from the Middle Jurassic of Liaoning was placed in Asilomorpha. Most striking is the condition of wing venation which resembles that of the family Tettigarctidae within the order Homoptera. In addition, this species possesses a wide and fully developed pronotum, a large circular genitalia, the short basitarsal and second tarsal segments, the rather elongate third one, and the absence of onychia. Bearing these characters, it must be a representative of tettigarctids rather than a gadfly, and it is closely similar to Turutanovia karatavia Becker-Migdisova and Shuraboprosbole plachutai B.-M. wich were discovered from the Jurassic of Russia.