When male drone flies (Eristalis tenax (L.)) of the spring and summer generations stop dispersing, they settle within individual home ranges that provide them with sheltering, resting, basking, grooming, feeding, and mating sites. Away from its mating place, a resident male rarely responds to other insects. On its mating site, however, it is territorial, attacking alien species, such as bees, wasps, and butterflies, as well as conspecific intruders. Territorial duty is demanding, and resident males take rest periods outside their territories whenever they can. When prevented from doing so, either by sky conditions which confine them to the territory, or by crowding which eliminates many neutral sites, they become increasingly aggressive. Males on open, horizontal territories (e.g., in flowerbeds) are more likely to notice intruders, and therefore are more liable to attack them, than males on vertical territories (e.g., on broad-leaved shrubs). The aggressiveness of E. tenax has social and ecological ramifications beyond its own species, since bees may stop foraging and aphidophagous syrphids may not oviposit in places where drone flies are exceptionally active.

The North American members of the genus Operophtera Hübner (Lepidoptera: Geometridae) are revised to include three species: O. brumata (L.), O. bruceata (Hulst), and O. danbyi (Hulst). Operophtera occidentalis (Hulst) is now treated as a subspecies of O. bruceata. All species are illustrated and characters to distinguish the species are given. The most useful characters for separating O. brumata from O. bruceata include the following: (1) hindwing dorsal surface with discal dot, which is almost always visible on O. bruceata but absent from O. brumata; (2) forewing colour, which is grey-brown or light brown in O. bruceata but reddish-brown in O. brumata; (3) abdomen colour, which is golden-brown to brown in western O. bruceata but brown in O. brumata; and (4) the costa of the forewing ventral surface, which is usually golden-brown in O. bruceata but brown in O. brumata. The structure of the genitalia of these two species allows hybridization between O. bruceata males and O. brumata females, but not vice versa.Hypothesized species interrelationships between palaearctic and nearctic Operophtera are illustrated in a cladogram. Maps for the distribution of each species are also included.

In British Columbia, Canada, Dasineura oxycoccana Johnson (Diptera: Cecidomyiidae) was initially found on highbush blueberry, Vaccinium corymbosum L. (Ericaceae) and has recently become a pest of cranberry, Vaccinium macrocarpon Aiton, a crop that is often found in close proximity with blueberry. Previous work has shown no temporal isolation and a potential for gene flow between these two D. oxycoccana populations. However, important behavioural differences were observed suggesting the potential for host races or cryptic species. Host races and cryptic species differ in their degree of assortative mating and reproductive isolation from partial to complete. We assessed whether populations of adult D. oxycoccana on these two crops would discriminate against mates from different natal hosts. Mating experiments were conducted within the greenhouse in 2010 using small glass vials without host plants present. Our results show D. oxycoccana from cranberry and blueberry hosts displayed complete assortative mating in the absence of their host plants. Behavioural data collected from the different crosses suggest these two D. oxycoccana populations differ in sex pheromones and close-range 'courtship pheromones'. We conclude that D. oxycoccana populations on cranberry and blueberry in British Columbia are reproductively isolated and probably represent cryptic species.

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