Thirteen intact cynipine galls (Cynipidae) are identified from the significant late Pleistocene locality of Rancho La Brea, mostly within the range of approximately 30,000 to 48,000 14 C yr BP. Late Cenozoic cynipids have a poor fossil record; it is thus of great interest that the provisional dates for this fossil gall collection establish that these insects and their hosts were an important part of the late Pleistocene ecosystem in and around Rancho La Brea. Cynipine host specificity both verifies, as well as augments, the proportionally low record of plants recovered at Rancho La Brea in comparison to records of mammals, birds, and other fauna. Because galler and hosts represent extant species, their climate and habitat restrictions offer a good basis for making paleoecological inferences. In particular, they imply that many of the diverse habitats found in California today, or, at least plant associations with similar environmental restrictions, some presently a distance from the Rancho La Brea Tar Pits, existed in the vicinity of this locality during the late Pleistocene. This material also includes previously undescribed species, several of which are morphologically similar to extant comparative material that exhibits a “jumping” behavior, previously believed to be unique to Neuroterus saltatorius Edwards.

Three traditional tribes of Fordini, Pemphigini and Eriosomatini comprise Pemphiginae, and there are two subtribes in Fordini and Pemphigini, respectively. Most of the species in this subfamily live heteroecious holocyclic lives with distinct primary host specificity. The three tribes of Pemphigini (except Prociphilina), Eriosomatini and Fordini use three families of plants, Salicaceae (Populus), Ulmaceae (Ulums) and Anacardiaceae (Pistacia and Rhus), as primary hosts, respectively, and form galls on them. Therefore, the Pemphigids are well known as gall makers, and their galls can be divided into true galls and pseudo-galls in type. We performed the first molecular phylogenetic study of Pemphiginae based on molecular data (EF-1α sequences). Results show that Pemphiginae is probably not a monophylum, but the monophyly of Fordini is supported robustly. The monophyly of Pemphigini is not supported, and two subtribes in it, Pemphigina and Prociphilina, are suggested to be raised to tribal level, equal with Fordini and Eriosomatini. The molecular phylogenetic analysis does not show definite relationships among the four tribes of Pemphiginae, as in the previous phylogenetic study based on morphology. It seems that the four tribes radiated at nearly the same time and then evolved independently. Based on this, we can speculate that galls originated independently four times in the four tribes, and there is no evidence to support that true galls are preceded by pseudo-galls, as in the case of thrips and willow sawflies.

Within the Aphidoidea, most species of Aphididae, as long as they are in small numbers and not carrying plant viruses, do little perceptible damage to their food plants. In species that cause toxicoses, it is usually assumed that some component of the saliva must be responsible. Paradoxically, however, the salivary enzymes of Aphididae are similar to those that already occur in plants – oxidases and enzymes that depolymerize polysaccharides – and the salivary enzymes are injected in very small amounts relative to their counterparts in the plant. Damage to plants triggers defensive, biochemical responses, and it is suggested that the injected enzymes serve mainly to divert or counter responses at the immediate interface of stylets and plant tissues. The saliva of Aphididae contains non-enzymic, reducing compounds which, in the presence of oxidases, can combine with and inactivate defensive phytochemicals – including those released in response to damage and transported in the phloem sieve tube sap on which Aphididae feed. Salivary and gut oxidases deactivate ingested phytochemicals by oxidative polymerization. Aphididae inject saliva into sieve tubes before sustained ingestion of sap, and this saliva has been presumed to condition the sieve tubes, but in what way remains unclear. It is suggested that there is a dynamic biochemical interaction between aphids and plants; that the interaction is usually well balanced for most of the Aphididae; hence, no outcome is readily observable. Where a significant imbalance occurs, however, either the aphid is unable to feed, i.e. the plant is resistant, and/or the aphid does not effectively counter a hypersensitive response. Not all plant responses are disadvantageous to aphids. Gall-forming Aphidoidea trigger and control abnormal growth in the plant to the insects' advantage, possibly by eliciting vigorous oxidation in selective meristematic tissues, thereby limiting supply of molecular oxygen and inhibiting oxygen-dependent growth-controls. Current problems and possible approaches for further research are reviewed.