The relationship between Segestidea novaeguineae and the strepsipteran parasite Stichotrema dallatorreanum is complex since the parasite (especially the totally en- doparasitic female) is totally dependent on the living host for its survival. Strepsiptera are a group of en- doparasitic, holometabolous insects. Females are wing- less while males have reduced forewings, fan-shaped hind wings and branched antennae. Their phylogenetic placement is still not clear. Based on morphological fea- tures and molecular data Strepsiptera have been sug- gested to be: a) sister group to Endopterygota (Kris- tensen 1995), b) belonging to Polyphaga Coleoptera (Crowson 1981), c) sister group to Coleoptera (Kinzel- bach 1971, Kathirithamby 1989), d) sister group to Diptera (Whiting et al. 1997). Strepsiptera are parasitic in as many as seven orders and 34 families of Insecta. In some species the female and male are parasitic in hosts belonging to different orders. The two free-living stages are the 1st instar larva and the adult male. A large number of eggs de- velop viviparously inside the endoparasitic, sac-like female. The 1st instar larvae crawl out to the open through the brood canal opening in the cephalotho- rax (the cephalothorax is extruded through the host cuticle). The free-living 1st instar larvae are either car- ried to the nests (in Endopterygote hosts), or wait for the hosts in the same habitat as where they emerged from the mother (in Exopterygote hosts). At the last larval instar the head and prothorax (cephalotheca) of the endoparasitic male extrude through the cuticle of the nymph or adult host and the male undergoes pu- pation. The female larva extrudes the cephalothorax and becomes a neotenic female. The free-living male emerges, leaving the empty puparium in the host, and mates with the neotenic female. The larvae develop viviparously within the female. The host is dramati- 197 T. DOUROUPI 1 , O. KONSTANDI 1 , J. KATHIRITHAMBY 2 & L. H. MARGARITIS 1 1 Dept. of Cell Biol. & Biophysics, Faculty of Biology, Univ. of Athens, Athens, Greece 2 Dept. of Zoology, Oxford Univ. Oxford, U.K. HISTOCHEMICAL AND MOLECULAR EVIDENCE OF PEROXIDASE ACTIVITY IN SEGESTIDEA NOVAEGUINEAE (BRANCSIK) (ORTHOPTERA) AND STICHOTREMA DALLATORREANUM HOFENEDER (STREPSIPTERA) Douroupi, T., O. Konstandi, J. Kathirithamby & L. H. Margaritis, 2001. Histochemical and molecular evidence of peroxidase activity in Segestidea novaeguineae (Brancsik) (Orthoptera) and Stichotrema dallatorreanum Hofeneder (Strepsitera). – Tijdschrift voor Entomologie 144: 197-202, figs. 1-7. [ISSN 0040-7496]. Published 1 December 2001. The system of host Segestidea novaeguineae (Brancsik) and the strepsipteran parasite Stichotrema dallatorreanum Hofeneder is a complicated one, since the parasite (especially the totally en- doparasitic female) depends on the living host for its survival. Chorion peroxidase has been studied in Diptera and is considered to play a crucial role in chorion hardening via the forma- tion of di- and trityrosine bonds. Peroxidase activity was detected in light and TEM sections of S. novaeguineae follicles and S. dallatorreanum embryos, stained with diaminobenzidine and H 2 O 2 . The endogenous fluorescence observed in the chorion may also be attributed to the pres- ence of such bonds. Mammalian and insect peroxidase specific primers were used in PCR reac- tions on host and parasite genomic DNA. Sequencing of PCR products revealed high similarities to insect peroxidases. Correspondence: Prof. Lukas H. Margaritis, Dept. of Cell Biology and Biophysics, Faculty of Biology, Univ. of Athens, Panepistimiopolis, Athens, Greece. E-mail: lmargar@biol.uoa.gr Keywords. – Strepsiptera; peroxidase; chorion