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Lasioglossum is a large genus of halictid bees with high species diversity in morphologically rather cryptic species groups. With more than 1900 described species, the taxonomy of the genus is complex and largely unresolved in many regions. For practical reasons, systematic reviews are restricted in scope either geographically or to particular species groups. In this study we focus on the subgenus Dialictus of the genus Lasioglossum from the Yucatán Peninsula in Mexico. In previous studies we identified members of the genus as important pollinators of cash crops in the region, and genetic analyses suggested the existence of seven molecular taxonomic units (mOTU). Based on additional morphological differences, we here describe these mOTUs as novel species, Lasioglossum (Dialictus) yucatanense Landaverde-González sp. nov., L. (D.) paxtoni Landaverde-González sp. nov., L. (D.) ameshoferi Landaverde-González sp. nov., L. (D.) aureoviride Landaverde-González & Husemann sp. nov., L. (D.) paralepidii Gardner sp. nov., L. (D.) milpa Landaverde-González sp. nov. and L. (D.) nanotegula Landaverde-González & Husemann sp. nov., and provide keys and images to assist in their identification.

The justification of the 4 genera that currently compose the class Pavlovophyceae is based on a low number of species and a relative paucity of available, traceable and referenced cultures. Previous integrative phylogeny work revealed strains that can refine and strengthen our knowledge of the genera in the class. The application of multiple light and electron microscopy techniques allowed us to prioritize the cytomorphological characters (pyrenoid, thylakoid, stigma, knob-scales, life stage / life cycle) used for the taxonomy of these algae and to describe two new species: Exanthemachrysis fresneliae Véron sp. nov. and Rebecca billardiae Véron sp. nov. Consequently, revisions of the two genera Exanthemachrysis Lepailleur emend. Véron and Rebecca Green emend. Véron were made. In addition, the genus Pavlova Butcher emend Véron is revised in the light of these characters. Particular emphasis is placed on the life stages and habitat of the species.

Among the 40 genera of Barychelidae, only nine genera are described from the African continent. Thorell (1899) described Ammonius Thorell, 1899 based on a male from Cameroon. In 1965 Benoit added more information from the holotype, with detailed illustrations of the male palp bulb and the eye group. Since then, few taxonomic revisions or new species of Barychelidae have been proposed from the African continent. Ammonius can be distinguished by the strongly pronounced retrolateral lobe of the male cymbium and the aspect of the bilobed spermathecae of the female. We redescribe the holotype male of A. pupulus Thorell, 1899 and describe the female for the first time. Additionally, a new species is described: Ammonius benoiti sp. nov., from Ivory Coast. The morphology of the tarsal setae is presented through SEM photographs. New distribution records of the genus are provided.

Seven new species of Schismatothele Karsch, 1879 (Araneae, Theraphosidae) are described, almost doubling the diversity of the genus: S. caeri sp. nov.; S. caiquetia sp. nov.; S. merida sp. nov.; S. moonenorum sp. nov.; S. quimbaya sp. nov.; S. timotocuica sp. nov. and S. wayana sp. nov. An identification key for all species of Schismatothele (except S. kastoni) is presented, as well as a complementary diagnosis for the genus. Also, a standardized nomenclature is proposed to describe the prolateral keels of male palpal bulbs of species of Schismatothele.

Six species of bopyrids were detected from the examination of hermit crabs collected along the Atlantic coasts of Mexico and deposited in the Colección Nacional de Crustáceos housed at the Universidad Nacional Autónoma de México. Asymmetrione tuxtlaensis sp. nov., the third species of the genus from the west Atlantic, is described. The occurrence of Asymmetrione desultor, Pseudostegias atlantica and Stegias clibanarii are recorded for the first time from the Mexican Atlantic coasts and the distribution range of the last two species is extended. Both a new host and three new localities for Mexico are reported for Anathelges hyptius and Bopyrissa wolffi, respectively. Distribution and reproductive data are provided for all six species examined. A key to genera and species of bopyrid isopods that parasitize hermit crabs in the Mexican Atlantic is provided.