Although Lygus hesperus Knight and L. lineolaris (Palisot de Beauvois) (Hemiptera: Miridae) are extremely destructive pests of a large variety of crops, the exact nature of their feeding adaptations remains unresolved. We studied the digestive enzymes in the salivary gland complex and guts of L. hesperus and L. lineolaris to elucidate the feeding mechanism and to determine the relative zoophagous and phytophagous potential of each species. Most of the digestive enzyme activity in both species originated in the salivary gland complex rather than the gut. We found general protease activity in the salivary gland complexes and guts of both species, with the predominant activity in the salivary gland complexes. Trypsin-like enzyme activity was the predominant alkaline protease in both species, but L. hesperus had significantly more activity than did L. lineolaris. In both species trypsin-like activity was greater in the salivary gland complex than in the gut. Some elastase-like activity occurred in both body regions of both species, and there was no chymotrypsin-like activity in either body region of either species. Both α-amylase (EC 3.2.1.2) and pectinase (EC 3.2.1.15) were present in both regions but were predominant in the salivary gland complexes of both species, but activities of both enzymes were significantly greater in L. lineolaris than in L. hesperus. Both species lacked α-glucosidase (EC 3.2.1.20) in the salivary gland complex, but both had considerable activity of this maltose-and sucrose-digesting enzyme in the gut. Also, both species had phospholipase C (EC 3.1.4.3) activity in the gut but none in the salivary gland complex. Both species had very low to negligible lipase (triacylglycerol lipase, EC 3.1.1.3) contents in the gut and no measurable lipase in the salivary gland complex. Hyaluronidase (3.2.1.35) activity was lacking in both species' salivary glands and guts. These enzyme profiles suggest that both species are well suited for phytophagy, but that L. lineolaris may be slightly better suited to strict herbivory.

Cacopsylla pyricola (Förster) is one of the most important pests of pear in North America, where several native predators have been considered for integrated pest management (IPM) programmes. Two molecular markers of 271 and 188 bp were developed from C. pyricola cytochrome oxidase I (COI) fragments, in order to study the detection of this species in the gut of arthropod predators. Primer sensitivity and the detection period for pear psylla remains in the guts of Anthocoris tomentosus Pericart were determined. The sensitivity threshold was defined at 10^-5 dilution of a C. pyricola fifth-instar nymph in all samples. Predator adults were evaluated immediately after ingestion of one to five C. pyricola nymphs (t = 0) and after 2, 4, 6, 8, 16, 24 and 32 h. Detection of the presence of C. pyricola DNA always lasted longer using the shorter fragment and was observed after 32 h of digestion using both markers. The primers amplifying the 188 bp fragment amplified all four psyllid species tested, whereas the primers designed to amplify the 271 bp fragment did so exclusively for C. pyricola and its close relative, Cacopsylla pyri (Linnaeus). Both primers failed to amplify DNA from representative species of the Coccinellidae, Chrysopidae, Hemerobiidae, Anthocoridae, Miridae, Salticidae, Aphididae, Tetranychidae and the Tortricidae, suggesting their suitability for general trophic studies.