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ŠUMARSKI LIST 11-12/2016 str. 24     <-- 24 -->        PDF

Iponemus gaebleri, Dendrolaelaps quadrisetus and Histiostoma piceae:
Using the Mannn-Whitney U-Test it could be shown that Iponemus gaebleri specimens per beetles of I. cembrae (both sample types summarized) are statistically significantly higher than numbers of the same mite per beetles of I. typographus. Summarizing the two sample types of I. cembrae (beetle mothers in their galleries and flown out young beetles) for a comparison with I. typographus was appropriate, because numbers of I. gaebleri mites on these two types of I. cembrae samples were found being statistically equal.
Dendrolaelaps quadrisetus was only found on the two types of I. cembrae beetle samples. There was no significant difference between numbers of D. quadrisetus on parental beetles collected out of their galleries and young emerged beetles from the wood blocks stored in the climate chamber.
Histiostoma piceae deutonymphs could only be discovered on one of the two Ips cembrae samples (emerged young beetles). Thus comparisons with other beetle samples were not workable.
4) Qualitative observations on mites attached to Ips typographus from Jastrebarsko
The Ips typographus-samples from Nova Gradiska, Gospic und Jastrebarsko were concluded for our statistical analysis. But the samples, collected in Jastrebarsko, enabled additionally some qualitative findings. There numerous felled tree trunks of Picea abies layed besides each other and contained different developmental stages of the beetle close each other (Table 1).
None of the larvae of I. typographus carried any phoretic mites. Also freshly hatched young beetles were free of mites. These beetles were unequivocally recognized as freshly hatched due to their still not yet sclerotized cuticles. Iponemus gaebleri as representant of the Tarsenomidae appeared, contrary to findings in our other collecting areas, unusually rarely. Only 2 out of 37 (23 older adult beetles, presumably parental beetles, 14 freshly hatched individuals and 20 larvae) beetles carried I. gaebleri individuals (table 1). Representatives of other mite groups were not found attached to the older parental beetles. Instead, specimens of Histiostoma piceae appeared inside the galleries in different developmental stages. Also I. gaebleri specimens had colonized that substrate. There were not enough data available for a statistical evaluation.
5) Mite developmental stages inside the bark samples with galleries of I. typographus and I. cembrae
5.1.) preferred areas of mite instars inside the bark beetle galleries
Iponemus gaebleri specimens were often discovered in greater numbers in bark pieces with I. typographus galleries (Fig. 5 A, B, G), up to 100 specimens in about 20 out of about 80 cases. Adults and quiescent young adults still in their larvae’s cuticles appeared in greater aggregations on decomposed dead bodies of I. typographus. These cadavers represented either freshly hatched young beetles or still pupae. Both had retained inside their pupa chambers. There, groups of 18-20 quiescent mite adults in larva-exuviae could sometimes be found (Fig. 5 B). Adults were crawling around in smaller numbers. Mold growth partly covered the areas around those chambers.
Histiostoma sp. was typically discovered in the same areas (Fig. 6 E). Only adult females could be found there. The species is characterized by a dorsal setation reminding to mites of the Genus Glyphanoetus. It is unknown, whether H. sp. reproduces thelytokously or whether males are only rare and were overlooked. Their preferred habitats were slightly moist, rich of bacteria and fungal hyphes (mostly mold fungae). It was not directly observed, which food this histiostomatid preferred. Almost one hundred percent of these mite specimens were remarkable covered by fungus spores (see next chapter).
Histiostoma piceae could be reared in greater numbers in the original bark substrate of both beetles, I. typographus and I. cembrae. It was observed that most specimens preferred the areas close to their beetle carriers, which were additionally kept