| Insects and ferns have a long history of more than 400 million years on the planet earth.However,the studies of the relationship between the two are still scarce compared with those studies between insects and angiosperms.Sclomina erinacea(Hemiptera,Reduviidae)is the natural enemy of many herbivorous insects,Hypolepis punctata(Dennstaedtiacea)is a common species of ferns in China.In the field study of multiple locations in China,we observed that S.erinacea often appeared themselves on the leaves of H.punctata,and hunted for Lepidopteral larvae.Thus,we assume that there is some kind of relationship between H.punctata and S.erinacea.To test this hypothesis,we conducted a series of study,which include recording the life history of S.erinacea,observing the antenna of S.erinacea under scanning electron microscopy,collecting and analysing the VOCs of H.punctata,testing the EAG responses of the antenna of S.erinacea to VOCs of H.punctata,testing the odour preference of the natural enemy to some VOCs of this fern species.We hope that this study will provide evidence for further study of the tritrophic relationship between H.punctata,S.erinacea and herbivory insects.The main results are as follows:1.S.erinacea have one generation per year in Hunan province,living through the winter in the adult stage.there are four instars for nymphs.Morphological observation showed that the color of the first instar nymphs was light yellow,and the second to the forth instar nymphs were light green.adult emergence happened in August,and adults were with the color grayish brown.The color change of S.erinacea went with H.punctata,making the leaves of H.punctata become good cover for the assassin bug.2.Observation of the antenna of S.erinacea under scanning electron microscopy showed that the antenna consists of five segments.Three types of antennal sensilla were observed,they are:sensilla trichodea,sensilla basiconca and sensilla chaetica.The sensilla distributed mainly on the flagellum,very few distributed on the pedicel,and no sensilla was found on the scape.No significant difference was observed between the male and female in the type and distribution of the antennal sensilla.Only one type of protarsal sensilla chaetica was observed on the surface of the protarsus,which may be related to the preference of S.erinacea to stay on the leaves of H.punctate.3.We collected the VOCs from herbivore-damaged and undamaged H.punctata using open dynamic headspace system.The result of the GC-MS analyse showed that the amount of 4 VOCs released from herbivore-damaged individuals was significantly greater than that from undamaged individuals.which include?-Myrcene,Linalool,a-pinene and Nonanal,we assumed they are herbivore-induced VOCs.we also found that herbivore-damaged H.punctata reduced the release of some other VOCs,which were released greater from undamaged individuals.4.The result of the EAG responses of the antenna of S.erinacea to five kinds of induced VOCs and two kinds of GLVs from H.punctata showed that the EAG responses of the antenna to three induced VOCs and two GLVs were significantly higher than responses to Hexane,which means that S.erinacea can sense these VOCs.5.The behavioral experiments using Y-tube olfactometer to test the attractiveness of the seven compounds above to the assassin bug showed that the attractiveness of four VOCs,which include Nonanal,13-Myrcene,2-Hexenal,(E)-and Linalool,from H.punctata to S.erinacea were stronger than Hexane,which indicate that some VOCs from H.punctata can attract S.erinacea. |
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