Symposium papers on

Strepsiptera presented at the XXI

International Congress of Entomology

Foz do Iguaçu, 20-26 August 2001

Tijdschrift voor Entomologie Netherlands Journal of EntomologyDownloaded from Brill.com10/02/2021 11:16:12AM Volume 144 (2) 1 December 2001 via free access Scanning electron micrograph of a free-living 1st instar larva of Stichotrema dallatorreanum Hofeneder emerging from within the body cavity of its mother, through an invagination, into the apron/brood canal. Scale 10µm. Reproduced from Kathirithamby, J. 2000, Journal of the Linnean Society 128: 274, with permission of the Linnean Society.

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INTRODUCTION of and the dual host nature of the Myrmecolacidae. Such a revision can only be achieved by molecular means. In this issue we see the first attempts to provide additional molecular infor- mation on several species of Myrmecolacidae (Halbert et al. pg. 179). By mitochondrial and nu- It gives me great pleasure to write the introduction clear phylogenetic analysis two new female to this special issue on Strepsiptera. The papers here Myrmecolacidae parasitic in Orthoptera (Tettigo- published were presented at the XXI International niidae) from Papua New Guinea have been identi- Congress of Entomology, at Foz do Iguaçu, in Brazil fied, and their relationship with Stichotrema dallator- between 20–26August 2000. reanum Hofeneder (a strepsipteran of economic importance) established. By the same analysis, the re- There are nine families of Strepsiptera and 580 lationship between male fenyesi Pierce (a species have been described so far. Most of the families strepsipteran parasitic in the red imported fire-ant in are cosmopolitan in distribution and some of the host Southern USA), and a female parasitic in a cricket in species are pests of crops. Strepsiptera exhibit extreme Texas (originally thought to be female C. fenyesi) is es- sexual dimorphism: adult males are free-living, while tablished. Two other species, Elenchus japonicus Esaki the females are neotenic and totally endoparasitic in & Hashimoto () and Xenos vesparum Rossi their hosts (except in the family ). They () are treated as paraphyletic outgroups to are a little-studied group, since they are difficult to the myrmecolacid ingroup in these analyses. This is find and collect. Most of the described species are free- the first time molecular data from three families of living males that have flown into traps. However, at Strepsiptera, and species within the Myrmecolacidae present we know of sites where fresh material can be have been analysed. collected. Molecular and developmental studies of this group are therefore being carried out. The difficulty of We see here as well, the first integration of molecu- obtaining material and the unique morphology have lar information into systematic and taxonomic de- meant that the phylogenetic position of Strepsiptera scriptions. This is especially necessary when studying has been difficult to resolve. They have been placed as economically important species such as S. dallatorre- a sister group of the Coleoptera, within the Polyphaga, anum in Papua New Guinea. Two new species of fe- a sister group to the Rhipiphoridae and a sister group male Myrmecolacidae from Papua New Guinea para- to the Diptera. This ‘Strepsiptera problem’ has in- sitic in two species of Tettigoniidae are described trigued evolutionary biologists. Huelsenbeck (pg. (Kathirithamby et al. pg. 187). The two new species 165) says that the quality and quantity of morpholog- were collected when accessing the issue whether host ical data available are limited and it is molecular data reservoirs for S. dallatorreanum exist in the bush. that hold the promise to solving the problem. The only two ribosomal genes (18S and 28S) available pro- We are also beginning to unravel aspects of the duced different placements of Strepsiptera. In his pa- host/parasite interactions. Changes that the host in- per Huelsenbeck discusses the strengths and limita- sects undergo when parasitised (stylopised) are ad- tions of parsimony and maximum likelihood analyses, dressed by Douroupi et al. (pg. 197), who report pres- and concludes that more molecular data are needed to ence of chorion peroxidase activity (which is solve the phylogenetic placement of Strepsiptera. In responsible for the formation of an elastic eggshell in collaborations with Spencer Johnston (Texas A& M, ), on histochemical and molecular evidence, in USA) and John Huelsenbeck, we are extracting more i) the strepsipteran Stichotrema dallatorreanum Hofe- molecular data for future analysis. neder and, ii) the host Segestidae novaeguineae (Branc- sik) from Papua New Guinea. They suggest that it will One family that particularly astonishes many biol- be interesting to investigate the possibility of integrat- ogists is that of the Myrmecolacidae, in which the ing peroxidase inhibitors, such as phluoroglucinol in a males and females parasitise hosts belonging to differ- sustainable integrated pest management programme. ent orders. Female Myrmecolacidae are rarely found (six among the 98 Myrmecolacidae described), and Details of the development of the endoparasitic have been placed under the genus Stichotrema. The stages are also emerging. It is known that the en- females of the other three genera (Caenocholax, doparasitic developing male strepsipteran extrudes Myrmecolax and Lychnocolax) are still unknown. A the anterior region (cephalotheca) through the host thorough revision of the family Myrmecolacidae is re- cuticle prior to pupation, while the female extrudes quired because the validity of the four genera is un- the anterior region (cephalothorax) through the host certain: this is due to the extreme sexual dimorphism cuticle prior to becoming a neotenic female. The

163 Downloaded from Brill.com10/02/2021 11:16:12AM via free access T  E,  144, 2001

male strepsipteran pupates and emerges as a free-liv- that five species of hornets were attracted to bait traps ing male, while the neotenic female remains endopar- in Ibaraki Prefecture, Japan, but only one species, asitic (except in the Mengenillidae) and produces vi- Vespa analis insularis Fabricius, was the dominant viparous 1st instar larvae while the host remains alive. host of Xenos moutoni De Buysson. He discusses the The male and female strepsipteran only extrude changes between 1998 and 2000 in levels of para- through certain abdominal segments of the host. sitism and the sex ratio of X. moutoni in the Japanese Obviously the strepsipteran moves within the host to hornet V. analis insularis. enable itself to extrude at these specific host abdomi- nal segments. Maeta et al. (pg. 203) discuss the posi- Finally, I dedicate this issue to the late Nadia tion prior to, and after, extrusion of the cephalotheca Waloff, my best friend and cherished mentor. As her and cephalothorax through the host cuticle of the research student I received from Nadia ‘abnormal’ strepsipteran Pseudoxenos iwatai Esaki when parasitis- Homoptera to identify. When dissected they were ing three species of eumenid wasps in Japan. found to be parasitised by Strepsiptera. The question how a parasite/parasitoid could cause drastic changes in Aspects of the ecology and sociobiology are also be- the physiology, morphology and behaviour in a host ing investigated. When parasitising Hymenoptera, and still not kill it (at least until the parasite’s life cycle only neotenic female Strepsiptera overwinter in their is complete) intrigued me then, and continues to in- female hosts. The timing of the emergence of these trigue me now. I learned a lot from Nadia, not only in stylopised females from hibernation is crucial because matters entomological but also from her honest, the viviparous free-living 1st instar larvae have to find straightforward nature. She was an example to us all. enough host larvae in the nests for them to parasitise. Sex ratios and percent parasitism can therefore be var- ied throughout the season. Makino (pg. 217) found Jeyaraney Kathirithamby

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