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Blue spruce (Picea pungens) has been planted in urban greenery as an ornamental tree in central Europe for more than 150 years. We investigated whether this nonnative spruce is a convenient habitat for ladybirds (Coleoptera, Coccinellidae). In 2021 and 2022, adults and larvae were sampled in four towns in Slovakia at monthly intervals throughout the growing season, from April to October. We recorded adults of 27 species and larvae of 11 ladybird species. Conifer specialist ladybird species predominated both in adult and larval communities (adults – 9 species, 85.2% of all individuals; larvae – 7 species, 92.1% of all individuals). Exochomus quadripustulatus and Aphidecta obliterata were the most common in adult (31.8% and 33.5% of all individuals, respectively) and larval (57.5% and 25.1% of all individuals, respectively) communities. The most abundant generalist species was nonnative invasive Harmonia axyridis (adults – 5.6%, larvae – 6.8% of all individuals). Adults and larvae of ladybirds were more abundant on solitary trees than on trees growing in groups. Our results confirmed that blue spruce hosts rich ladybird communities and provides them shelter and food resources.

Understanding of habitat favourability has wide relevance to the invasion biology of alien species. We studied the seasonal dynamics of the alien ladybird Harmonia axyridis (Coleoptera: Coccinellidae) in monoculture Scots pine forest stands in south-west Slovakia, Central Europe, from April 2013 to March 2015. Adult H. axyridis were collected monthly across seven randomly selected pine stands of different ages and canopy closure, from the lower branches of pine trees, and larvae were recorded qualitatively. Adults were recorded all year round, most abundantly in November and least abundantly in February. The relationship between the abundance of H. axyridis and selected forest stand characteristics was modelled using the negative binomial Generalized Additive Model with penalized spline component in month (seasonality) effect, year, canopy closure and age effects and the random effect of forest stand (sample area effect). The abundance of H. axyridis was significantly influenced by the age of stand and seasonality (with month granularity) for both closed and open canopy stands, whereas the effects of canopy closure and sample area were not significant. The bimodal pattern of seasonal dynamics of H. axyridis on Scots pine was common for closed and open canopy stands, with two peaks reflecting the cyclic movement of the species from and to overwintering sites. Harmonia axyridis utilized certain pine stands preferably for foraging during the growing season and certain stands for refuge during winter. The ladybirds were found in highest numbers in the 15 year old closed canopy stand (overwintering site). The occurrence of both adults and larvae in most stands indicated a suitability of Scots pine forest for ladybird breeding. The model of year-round dynamics of H. axyridis has been presented for the first time within the invaded range of the ladybird in Europe.

Many species of ground beetles (Coleoptera: Carabidae) are important predators of seeds. While the consumption of herb seeds has been intensively studied, little attention has been paid to the consumption of seeds of gymnosperm plants. Here, we determined the consumption of seeds of six coniferous species by four common carabid species and compared carabid preference for conifer and selected common angiosperm weed seed species. In no-choice experiments, the large carabid species Pseudoophonus rufipes preferentially consumed the seeds of Picea abies, Larix decidua and Pinus sylvestris. Pinus sylvestris was also preferred by another large carabid, Pterostichus melanarius. The smaller carabids Harpalus affinis and H. rubripes consumed conifer seeds reluctantly. The intensity of seed consumption by carabids decreased with increasing seed size. In choice experiments, both of the large carabid species preferred the small conifer seeds of P. sylvestris and L. decidua over herb seeds of similar size (Dipsacus fullonum, Galeopsis speciosa, Polygonum lapathifolium). Carabids may prefer conifer seeds because of their soft seed coats, regardless of their chemical protections. Postdispersal predation of seeds by carabids may be an important mortality factor in some conifer species.