Distribution and Biogeography of the Order Raphidioptera: Updated Facts and a New Hypothesis
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Acta Zool. Fennica 209: 33-44 ISBN 95 1-9481-54-0 ISSN 0001-7299 Helsinki 6 May 1998 O Finnish Zoological and Botanical Publishing Board 1998 Distribution and biogeography of the order Raphidioptera: updated facts and a new hypothesis Worst Aspock Aspock, H., Department of Medical Parasitology, Clinical Institute of Hygiene, University of Vienna, Kinderspitalgasse 15, A-1095 Wien, Austria Received 8 October 1997 The known distribution of extant Raphidioptera is restricted to the Holarctic, with the exception of the north and east of America. So far 204 valid extant species are known, 3 1 of which have been described within the past ten years, but the real number may exceed 250. Phylogenetic results indicate that the Raphidioptera of America derive from a Mesozoic fauna established before the separation of South America from Africa and the break-up of Laurasia. This fauna was much richer than the extant one, and snakeflies also occurred in tropical climates and in the Southern hemisphere. It is hy- pothesized that, due to the extraterrestrial impact at the end of the Cretaceous, 65 mil- lion years ago, all lines adapted to tropical climates became extinct and only those adapted to cold climates (Raphidiidae, Inocelliidae) survived. 1. Introduction Ghang 1989, Nel et al. 1990, Oswald 1990, Chang 1992ab, Martins Neto & Vulcano 1992, Martins The distribution of the Raphidioptera has been Neto & Nel 1993, Nel 1993, Ren 1994, 1995, discussed extensively. These insects are confined Willmann 1994), which also lead to new consid- to the Northern hemisphere, and in America they erations on the genesis of the distribution of ex- occur only in the southwestern parts of North tant snakeflies. America. Explanations of this pattern, and hy- The aim of the present paper is to update, sum- potheses on its genesis, have been discussed and marize, and review data on the distribution of reviewed in our monograph (Aspock et al. 199 1) Raphidioptera and to present some new hypotheti- and also in a later paper (Aspock & Aspock 1994). cal considerations on mechanisms which might During the past 8 years, further progress has been have been significant for the extant distribution achieved in the documentation and study of the of these insects. Raphidioptera of many parts of the world (Aspock & Aspock 1990,1991,1993,1995,1996, Rausch & Aspock 1991, 1993, Aspock 1992, Aspock et 2. Basic systematic and biological facts al. 1992,1994ab, 1995,1997ab, Aspock & Holzel 1996). Moreover, a considerable number of fos- The Raphidioptera are a small order comprising sils have been found in various regions (Hong & two well-characterized families, the Raphidiidae 34 Aspock ACTA ZOOL. FENNICA Vol. 209 (with 183 described and valid species) and the be very suitable). In captivity, larvae have also Inocelliidae (with 21 described and valid species). been found to nibble on dried or decaying plant Snakeflies are confined to arboreal habitats (at material. Adults have often been observed feed- least those with bushes) and to latitudes andlor ing on pollen. They will also readily take various altitudes with acold winter period. Larvae of many artificial diets, e.g. mashed banana and other fruits. species of Raphidiidae and (probably) of all Thus, both larvae and adults may be classified as Inocelliidae live under the bark of trees and shrubs carnivorous, with a tendency to omnivory in cer- and in crevices of (living) wood. The larvae of tain situations. some Raphidiidae live in the top layer of soil (e.g. Adults of Raphidioptera are poor flyers and in the leaf litter) around the stem and the roots of show an extremely low vagility and thus capacity shrubs. A few species are apparently also capable for dispersal. According to our experience in the of living in rock crevices. field (we have certainly observed several ten thou- The developmental period from egg to adult sands of snakeflies of most extant species during stage lasts at least one year (genus Raphidia L. the past 35 years), Raphidioptera rarely intention- and, rarely and exceptionally, species of other ally cross an open meadow, usually not even leav- genera), in most species of Raphidiidae two or ing "their" tree or shrub. three years, and in most Inocelliidae three years or longer. The number of moults in the larval stage is not fixed (it may vary even within a species 3. Known distribution from 10 to 15) and the duration of the larval pe- riod is also variable. Under experimental condi- Figs. l and 2 show the presently known distribu- tions, prolonged developmental periods of up to tion of the extant representatives of the order six (or even seven) years have been observed in Raphidioptera. It comprises probably almost all some Inocelliidae. Adults usually, however, live arboreal parts of the Palaearctic region, including only a few days; males probably die soon after transition areas to the Oriental region, with the copulation, but females may live possibly up to southernmost records (in higher altitudes) in Mo- two or three weeks if the oviposition is delayed rocco, Northern Algeria, Northern Tunisia, Israel, due to unfavourable weather conditions. Syria, Northern Iraq, Northern Iran, Northern Paki- As far as it is known, all species of both families stan, Northern India, Bhutan, Burma, Northern need a period of low temperature (around or below Thailand, and Taiwan. In large parts of the north- 0°C) which seems to be important for inducing ernmost regions of the European part of Russia, pupation or hatching of adults. Under experimen- as well as in the large northern parts of Siberia, tal conditions, the withholding of low tempera- no snakeflies have been recorded. Nevertheless, tures leads to prothetely of larvae or death of pupae. there is no doubt that the whole forest belt of north In most Raphidiidae and Inocelliidae, pupa- Asia is inhabitedby snakeflies (although by a few, tion takes place shortly after overwintering of the probably only three, species). Ovalarge areas no- last larval stage; adults appear in late spring or body has ever looked for Raphidioptera, but the early summer. In some Raphidiidae (e.g. species few records may, however, be regarded as repre- of the genus Alena), delayed pupation after hlber- sentative; moreover, in Northern Europe those nation of the last larval stage occurs; adults ap- three species which are also known from Siberia pear in summer (or later). In some Raphidiidaepu- occur as far north as forests can grow. pation takes place in autumn; adults hatch in spring. In the Nearctic, the distribution is restricted to Larvae (and adults) of all snakeflies are car- the southwestern and southern parts of North nivorous, feeding on a great variety of mainly soft- America. The southernmost records are from the skinned arthropods, particularly eggs and larvae Mexican/Guatemalan border and these are the of various insects or softbodied adults (e.g. most southerly records of extant snakeflies. The aphids), but, at least under experimental condi- northernmost records are from the southern parts tions, they also consume any dried organic matter of British Columbia at about 53"N, and, in the with a high amount of protein if one adds some northwest, snakeflies reach the limit of their dis- water (concentrated "energy-food has proved to tribution in Alberta, Montana and Wyoming. Only ACTA ZOOL. FENNICA Vol. 209 Raphidioptera: updatedfacts and a new hypothesis 35 Fig. 1. Documented distribution of the family Raphidiidae (updated map from Aspock et al. 1991). in the south, in Texas and in Mexico, the distribu- first species by Linnaeus 240 years ago up to 1997. tion reaches almost to the Atlantic coast. The east- There is a distinct rise in the slope of the curve ern states of the USA (east of Montana, Wyoming, from the middle of the sixties about 35 years ago Colorado, New Mexico and Texas) lack snakeflies when we started our work on the group. Now a entirely. It is also of particular interest that Alaska number of 204 valid species has been reached, does not harbour any snakefly - despite appar- but descriptions of further species are in progress. ently optimal ecological conditions. Throughout the past 30 years and even a few years In the northern parts of their distribution area, ago we (Aspock et al. 1991 and many of our pre- Raphidioptera also occur in the lowlands. In the vious publications) have always estimated the real southern parts they are restricted to higher alti- number of extant species as not exceeding 200. tudes and are to be found even above 3 000 m This figure has to be corrected now. After further (Aspock et al. 1991,1992, Aspock & Aspock 1994, intensive field studies in various parts of Europe, H. & U. Aspock unpubl.). Asia and Mexico in recent years (after the publi- The distributions of the two families are very cation of our monograph) one may conclude that similar (Figs. 1 and 2). From this it may be con- the snakefly faunas of America and of the west- cluded that the mechanisms which have led to ern Palaearctic have been almost completely docu- these distributional patterns may be identical or mented, but Asia still harbours a considerable at least similar in the two families. number of species to be detected (Aspock et al. 1997b).The latest realistic figures and estimations are 183 described, but at least 220 really existing 4. Number of known species species of Raphidiidae, and 21 or 30 Inocelliidae. Thus, our planet is presently inhabited by prob- Fig. 3 shows the progress in the documentation of ably at least 250 species, possibly almost 300 spe- known Raphidioptera from the description of the cies of Raphidioptera. Aspuck ACTA ZOOL. EENNICA Vol. 209 Fig. 2. Documented distr~butionof the family Inocelliidae (updated map from Aspuck et al.