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ŠUMARSKI LIST 11-12/2016 str. 21     <-- 21 -->        PDF

of mites phoretically found on I. typographus were additionally statistically compared with mites which were discovered attached to I. cembrae.
Evaluation of samples and mite cultivation – Evaluacija uzoraka i kultiviranje grinja
Numbers of different phoretic mites on bark beetles were counted using a Zeiss-Stereo microscope. For this purpose, living beetles were carefully held with fingers or a spring tweezer, and mites, visible from outside, were counted. This procedure was practiced to secure that mites stay in their original positions. In contrast to that, dead beetles in alcohol usually lose most of their mites. But for this research, it was important to determine the different beetle areas of mite attachment. For this reason we divided the beetle body in Table 4 into head, thorax, Abdomen, coxae 1-3 and elytral declivity in order to define the mite’s positions.
On a random basis, beetles in alcohol were observed (about 15 beetle specimens per species) for mites under their elytrae, where we didn’t discover any mites. Additionally, living mites attached to beetles, which died under natural circumstances, were counted for comparisons. Beetles with and beetles without mites were kept in different dishes (15 dishes per beetle species with at least 3 beetle individuals inside). Dishes with beetles, which carried mites, were used as mite cultivation wells to imitate natural conditions as far as possible and to stimulate the development of histiostomatid mites. These cultivation wells were prepared as follows: beetles were put into Petri dishes (60 mm in diameter) and equipped with bark pieces with galleries and original bore dust. Raw potato pieces were added and sprinkled with some water in a two-day rhythm to stimulate the growth of bacteria, which usually represent the food source for mites of the Histiostomatidae. The closed Petri dishes (60 mm Ø) and small plastic dishes (250 ml and 125 ml) were kept at room temperature (ca. 20 °C). Sufficient moisture (that potatoes were partly covered by a thin layer of „slime”) was guaranteed not only by a moist layer of pulp paper, but also due to the fact that both types of dishes were covered by plastic containers. Adults and free living instars besides the phoretic deutonymph need to be available for a useful determination of the species. Iponemus gaebleri Schaarschmidt, 1959 (Tarsenomidae) could develop inside the same dishes, in which histiostomatid mites were reared.
Key to larvae and protonymphs within the genus Histiostoma – Ključ za larve i protonimfe unutar roda Histiostoma
Histiostomatid mites develop often synchronously, thus in young colonies, adults and deutonymphs might be missing. This herewith introduced original key shall enable the identification of histiostomatid mites by their larvae and protonymphs. Tritonymphs are not included as their morphology appears to be variable throughout genera and species.
Many species and genera of the Histiostomatidae are based on the deutonymph morphology, only occasionally also adults were described. The whole set of developmental stages appears only rarely in species descriptions. Such descriptions and species studied by this author contributed to this key. It is based on phylogenetic comparative morphological comparisons concerning nymphal characters, which are named in the key. These characters were mapped on the phylogenetic tree of Wirth (2004). The following key of larvae and protonymphs is based on species of the following genera and species: Aphodanoetus, Bonomoia, Glyphanoetus, Myianoetus, Sarraceniopus, Histiostoma brevimanus Oudemans 1914, H. julorum Koch 1843, H. feroniarum Dufour 1839, H. sp. (ex sap flux Berlin, Germany), H. ovalis Müller 1860, H. piceae Scheucher 1957, H. sp. (ex rotting tree stump Saarland, Germany), H. sp. (ex rotting wood Vladivostok/ Russia).
Non-Histiostoma outgroup Astigmata were mites of the genera Acarus, Sancassania and Rhizoglyphus.
Statistical evaluation – Statistička obrada
The statistical evaluation of mite numbers attached to beetles and their preferred areas on these beetles was made using the software SPSS 15.0 for Windows (SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago, SPSS Inc.).
Mite numbers on different beetles were compared with each other using the Kolmogorov-Smirnov test and the Shapiro Wilk test to determine whether or not a random sample of values follows a normal distribution. Using these tests we evaluated numbers of mites per beetles in terms of the data sets „Ips typographus (total) and „Ips cembrae (total).
Using the Mann-Whitney Rank-Sum test for independant samples we compared the groups of beetles in regard of their numbers of phoretic mites.
1) Collected mite species and their preferred body regions of the beetles
Table 1: Ips typographus – samples from Jastrebarsko
Tablica 1: Ips typographus – uzorci iz Jastrebarskog
Mites phoretically attached to Ips typographus or found inside its galleries: Beetle specimens (parental beetles) for this evaluation were collected in nova Gradiska and Gospic. The most abundant mite was Iponemus gaebleri (Tarsenomidae, Fig. 5 C). The uropodid Urobovella sp. (Fig. 6 C) appeared once as a deutonymph on a beetle specimen. Dendrolaelaps quadrisetus (Fig. 6 B) and Histiostoma piceae (Fig. 5 D, E, F) could not be found atttached to any beetles, but appeared regularly as free living stages inside the gallery-samples.