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Based on the original research of 2017–2018, also reference data, four aphid species and five species complexes of the family Adelgidae listed for Lithuanian fauna. Pineus (Pineus) strobi (Hartig, 1839) is a new species for the fauna of Lithuania. Summarized information on the distribution and host specificity of adelgid species in Lithuania is presented. The most common species recorded from all geographical regions of Lithuania were the ones belonging to the species complexes Adelges laricis – A. tardus, Pineus orientalis – P. pini, Sacchiphantes viridis – S. abietis and Gilletteella cooleyi – G. coweni. Six species of Adelgidae inhabit host plants of the genus Picea, three live on Larix, three – on Pinus, two – on Abies, one – on Pseudotsuga. Partial sequences of mitochondrial (COI) and nuclear (EF-1α) DNA of Lithuanian samples were analysed in comparison with available data from GeneBank representing samples from Central Europe. Pairwise distances of COI and EF-1α fragments between samples belonging to species complexes Adelges laricis – A. tardus, Dreyfusia nordmannianae – D. piceae, Sacchiphantes viridis – S. abietis, Gilletteella cooleyi – G. coweni and Pineus orientalis – P. pini suggest each species complex being a single species.

Partial sequences of mitochondrial COI and nuclear EF-1α genes have been analysed across the Lithuanian samples of Rhopalosiphum padi and R. nymphaeae (Hemiptera: Aphididae). In addition, samples from the adjacent countries of the Eastern Baltic region of Europe (Latvia, Estonia and Poland) and available sequences from GenBank and Bold Systems were used. The range of intraspecific pairwise R. padi COI sample (n = 44) divergences (K2P model) was 0.00–2.49% (average 0.61%). Out of 10 haplotypes, one was predominant (n = 25), with Worldwide distribution. The range of intraspecific pairwise R. nymphaeae COI sample (n = 20) divergences (K2P model) was 0.00–1.31% (average 0.22%). Out of 6 haplotypes, one was predominant (n = 13), sampled in Lithuania, Ukraine and Turkey (Asian part). The range of intraspecific pairwise sample divergences (K2P model) of EF-1α fragment was 0.00–0.40% (average 0.10%) for R. padi (n = 20) and 0.00–0.60% (average 0.13%) for R. nymphaeae (n = 17). Two COI haplotypes (including the Worldwide distributed one) and three EF-1α haplotypes (including the most common one) were detected in Lithuanian populations of R. padi. The present study suggests that R. padi populations from the Eastern Baltic region are predominantly holocyclic.

Brachycaudus divaricatae (Hemiptera: Aphididae), a recent invader to Europe, has already reached Czech Republic. Partial sequences of mitochondrial COI and nuclear EF-1α genes have been analysed across the sixteen Czech samples of B. divaricatae, together with morphometric analysis of the same samples based on eighteen morphological characters of the apterous viviparous females. For comparative studies, thirteen samples from the Eastern Baltic region of Europe (Latvia, Lithuania and Poland) were used. All sampled populations appeared similar in their genetic and morphological characters studied. One haplotype of mitochondrial COI gene was predominant; it was characteristic for all samples from Czech Republic and 8 out of 13 samples from Eastern Baltic region. Two other haplotypes were found in the Eastern Baltic region only. Four different haplotypes of EF-1α gene were detected. Most of the samples (except one sample from the Eastern Baltic region and two samples from Czech Republic) had the same haplotype. Out of remaining three haplotypes, one was unique for the Eastern Baltic region, whilst two were found in Czech Republic only. For the present, Moravia is the southernmost region in Europe, where B. divaricatae has been already reported. Presumably, this invasive aphid species has entered the Czech Republic from the north via the Moravian Gate, a natural pass formed by the depression between the Western Carpathians and Eastern Sudetes.

Aphids of the species Cryptomyzus alboapicalis (Theobald, 1916) and Cryptomyzus leonuri Bozhko, 1961 are very similar morphologically, although exploit different host plants (Lamium album and Leonurus cardiaca, respectively). Morphological characters proposed for the separation of this species couple in the identification key to European Cryptomyzus species appeared to be of little discriminatory power when applied to apterous viviparous females from clonal lineages, whilst alate viviparous females of C. leonuri were not included in the key at all. The aim of this study was to find reliable morphological characters and their combinations for the separation of apterous and alate viviparous females of C. alboapicalis and C. leonuri. Forward stepwise discriminant analysis based on characters without statistically significant (P < 0.05) correlation (|r| ≥ 0.50) with body length resulted in canonical functions enabling correct classification of 95–100% of specimens from clonal lineages involved in the analysis with a priori specified group membership. The post hoc classification gave 95–100% correct identification of individuals from clonal and 85–100% from field-collected samples. The discriminative values of single morphological characters and canonical functions are discussed and modified key for the morphological identification of C. alboapicalis and C. leonuri apterous and alate viviparous females is suggested.