Three shrubby, succulent, spiny Euphorbia (Euphorbiaceae) species from western Saudi Arabia are described and illustrated as new: Euphorbia madinahensis Fayed & D.Al-Zahrani, Euphorbia saudiarabica Fayed & D.Al-Zahrani and Euphorbia taifensis Fayed & D.Al-Zahrani. Diagnostic characters, descriptions and taxonomic comments on each are given, and they are compared with closely related species. The geographical distribution of the three new species is shown.

The shrubby, spiny, succulent species Euphorbia collenetteae D.Al-Zahrani & El-Karemy (Euphorbiaceae) from the southern Red Sea coast and islands is described and illustrated as new. Diagnostic characters, a description and taxonomic comments on the species are given. It is compared with the closely related Euphorbia fractiflexa S.Carter & J.R.I.Wood. The geographical distribution of the new species is shown.

The habitat use and the phenology of the large grasshopper Acrostira euphorbiae García & Oromí endemic to La Palma (Canary Islands) are studied. This grasshopper is entirely dependent on the Canarian endemic shrub Euphorbia lamarckii both for food and to avoid predation. Adults stay on subapical branches during the day, probably to reduce the risk of predation, and climb up to the apex at night to feed. While females seem to ensure the genetic diversity of offspring by waiting for visits by different males, the latter have to move to guarantee their reproductive success. Monophagy in this species may be related to the year-round presence of tender shoots, and to the predator-repellent toxic latex found in the host plant. Unlike related species from continental areas, adults and nymphs of A. euphorbiae are present almost all year round, probably in adaptation to the particular climate of the islands. Nymphs are more abundant in winter, when Euphorbia leaves are most available. However, adults are more abundant than nymphs in spring, summer and autumn. Males develop more quickly than females, an apparent reproductive strategy based on achieving sexual maturity to coincide with females undergoing imaginal moulting. Matings start immediately after adult females emerge. Densities oscillated between 73 and 193 individuals ha−1, which can be considered a low value compared with other continental pamphagid species.

Euphorbia sect. Tithymalopsis (Euphorbiaceae) comprises seven species of herbaceous perennials restricted to the south-eastern USA. The species of sect. Tithymalopsis are united and distinguished from other sections in Euphorbia by having a thick and cylindrical root system, a glabrous cyathium, five glands with petaloid appendages, one to three stems arising from the root, absence of vestigial sepals in pistillate flowers, rounded leaf apices, and pitted or smooth seeds without a caruncle. Cladistic analyses indicate that sect. Tithymalopsis consists of two subgroups: (1) E. corollata, E. discoidalis, E. pubentissima and E. polyphylla; and (2) E. curtisii, E. gracilior and E. mercurialina. Comparative data from vegetative morphology, pollen morphology, seed morphology, cytology, crossability, reproductive biology, habitat and distribution are presented. Keys and descriptions to the species are provided.