The Diptera are the second most important order among flower-visiting (anthophilous) and flower-pollinating insects worldwide. Their taxonomic diversity ranges from Nematocera to Brachycera, including most families within the suborders. Especially important are Syrphidae, Bombyliidae, and Muscoidea. Other families, especially of small flies, are less appreciated and often overlooked for their associations with flowers. We have compiled records of their flower visitations to show that they may be more prevalent than usually thought. Our knowledge of anthophilous Diptera needs to be enhanced by future research concerning (i) the significance of nocturnal Nematocera and acalypterate muscoids as pollinators, (ii) the extent to which the relatively ineffective pollen-carrying ability of some taxa can be compensated by the abundance of individuals, and (iii) the role of Diptera as pollinators of the first flowering plants (Angiospermae) by using phylogenetic and palaeontological evidence. Specializations in floral relationships involve the morphology of Diptera, especially of their mouthparts, nutritional requirements, and behaviour, as well as concomitant floral attributes. The South African flora has the most highly specialized relations with dipterous pollinators, but in arctic and alpine generalist fly–flower relations are important in pollination and fly nutrition.

The Holarctic Scopula cajanderi (Herz) species group is revised on the basis of external and genitalic characters. The taxa included in the species group are Scopula cajanderi (Herz, 1903 [not 1904]) (= the Palaearctic Scopula elwesi sajanensis Prout, 1935 syn.nov., = the Palaearctic Scopula elwesi achlyoides Prout, 1935 syn.nov., = the Nearctic Scopula septentrionicola McDunnough, 1939 syn.nov.), thus making S. cajanderi Holarctic; Scopula mustangensis Yazaki, 1995; and Scopula aegrefasciatasp.nov. Lectotypes are designated for the following species which were described from more than one specimen without holotype designation: S. cajanderi, Scopula anaitaria (Herz, 1903), and S. e. achlyoides. The systematic position of Scopula elwesi elwesi Prout, 1922 within the genus Scopula is uncertain. A key to the species is presented with illustrations of the adults and genitalia, and a distribution map is presented for all taxa. An examination of the biogeography of S. cajanderi suggests that the Wisconsinan and Sartan glaciations may have played a part in the origin of the disjunct populations.

The Neotropical genus Acanthoscelio Ashmead is revised. We recognize eight species, found from Costa Rica south to Paraguay and southeastern Brazil. Acanthoscelio americanus Ashmead (Brazil) and A. flavipes Ashmead (Costa Rica, Panama, Venezuela, and Trinidad) are redescribed, and six new species are described: A. acutussp.nov. (Costa Rica, Colombia, Venezuela, Trinidad, Ecuador, Peru, and Brazil), A. latenssp.nov. (Ecuador), A. nimbosussp.nov. (Colombia, Ecuador, Peru, Brazil, and Bolivia), A. prolatussp.nov. (Colombia and Ecuador), A. punctatussp.nov. (Costa Rica, Panama, Colombia, and Ecuador), and A. radiatussp.nov. (Colombia, Ecuador, Peru, Brazil, and French Guiana). A key to species is provided.

The growth (increase in body mass) and development (progression to specific instar) of the bertha armyworm, Mamestra configurata Walker, were examined using up to 14 plant lines from five species of brassicaceous plants. Varietal and breeding lines of Brassica napus L., B. juncea L., B. rapa L., B. carinata L., and Sinapis alba L. were selected on the basis of differing seed and foliar glucosinolate levels. No-choice feeding experiments were conducted with larvae isolated on leaf discs, individual leaves, or entire plants of each line. The no-choice tests showed that M. configurata weight gain and development varied significantly among host plants tested. Two B. juncea lines (AC Vulcan and H-Allyl) and the S. alba lines (AC Pennant and L-GS) were the poorest hosts in terms of larval weight gain, and the two B. juncea lines also significantly slowed development relative to the other lines tested. Mamestra configurata feeding preference, which was examined using a series of paired leaf disc choice tests, was also significantly different among the lines examined. Two B. juncea lines (AC Vulcan and H-Allyl) were significantly less preferred than all the other lines examined. The data extends previous work indicating that specific foliar glucosinolates, such as sinigrin, which is predominant in B. juncea, and sinalbin, which is abundant in S. alba, may provide brassicaceous crops with some protection from M. configurata. Thus, it may be possible to use foliar glucosinolate levels as predictors of M. configurata feeding damage in the development of breeding lines for the genus Brassica.

The emergence patterns of Diptera breeding in small-sized and buried carrion were studied in rearing experiments with field-exposed baits. Development times are reported for 52 species in the families Phoridae, Sphaeroceridae, Sepsidae, Heleomyzidae, Anthomyiidae, Fanniidae, Muscidae, Sarcophagidae, Psychodidae, and Sciaridae. Most species showed a synchronous emergence of males and females. Protandry was detected in Hydrotaea ignava (Harris) (Muscidae), H. palaestrica (Meigen), and Psychoda minuta (Banks) (Psychodidae). Protogyny was found in several species of Phoridae, namely Conicera similis (Haliday), C. schnittmanni Schmitz, Anevrina unispinosa (Zetterstedt), and Triphleba dudai (Schmitz). Conicera schnittmanni and T. dudai showed two discrete emergence periods for each sex, which is due to a delayed emergence of some specimens. Protogyny is a rare phenomenon in Diptera and insects in general, and has never been reported before in Phoridae. The significance of protogyny could not be ascertained in the examined species, because of insufficient information on their mating systems and female receptivity patterns.

Factors that might contribute to variability in the densities of wheat midge eggs, Sitodiplosis mosellana (Géhin), on common and durum wheats, Triticum aestivum L. and Triticum durum Desf., were investigated to improve the quantification of oviposition preferences in relation to crop resistance. Egg densities on wheat spikes were highly variable, with a similar contagious distribution in the laboratory and field, although variance was highest in the laboratory. Females laid eggs in small groups, usually of one to six eggs; most infested spikes had more than one egg group. Females showed no preference for ovipositing on different parts of a spike, although spikelets on one side and at the base often received fewer eggs because these spikelets were covered by the flag leaf and inaccessible for longer than others. Oviposition rates varied from night to night, probably related to the weather. Females showed no preference for spikes at different growth stages, from the time spikes began to emerge until at least flowering. Spike size did not affect egg density, and spike height was a factor only for spikes deep within or protruding above the canopy. Sources of environmental variation such as effects of weather on oviposition rates in the field or spatial phenomena in cages were measurable but of secondary importance. In the field, comparisons among spikes which emerged on the same day could reduce variation in egg density. In the laboratory, variation in egg density could be reduced by using arrays of excised spikes arranged at the same height, leaving the central portion of the array empty. The primary cause of high variability in egg density among spikes was variation in egg-group size and the presence of multiple egg groups on a single spike, factors which cannot be experimentally controlled because they are the result of oviposition behaviour rather than environmental heterogeneity.

Females of Monoctonus paulensis (Ashmead), a solitary parasitoid of aphids, generally select the relatively smaller over equally available larger instars of the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphidoidea: Aphididae). Large hosts contain more resources for parasitoid development and hence have presumably higher quality; however, they require more time to subdue and are more likely to escape. We tested the hypothesis that a female’s choice among first (L1), second (L2), third (L3), and fourth (L4) instars of the pea aphid is based on the optimal balance between fitness costs in terms of time and fitness gains in terms of offspring number and size. Prepupal mortality did not vary with host instar, but pupal mortality was greater among parasitoids developing in L4 than in any younger instars. Offspring mortality was not influenced by clutch size in that mortality risk did not differ between parasitoids developing alone and counterparts developing in a clutch. The sex ratio, measured as proportion of daughters among offspring, was female-biased on all four host instars; the degree of bias increased from 0.70 (in L1) to 0.92 (in L4). Parasitoid body size was a function of aphid size at parasitism. Females were larger than males; the magnitude of the difference in body size was constant and independent of host and hence parasitoid size. A female’s potential fecundity as measured by the number of ovarial eggs at eclosion varied with her size and larval ontogeny. The four instars of the pea aphid were ranked in the order L1 > L2 > L3 > L4 both in terms of the number of offspring produced per encountered host and in terms of a female’s time costs; first instars are easier to handle and are more abundant in the field than older instars. The four host types were ranked in the order L2 > L3 > L1 > L4 in terms of the proportion and potential fecundity of daughters among offspring. The observed preference pattern (L1 > L2 > L3 > L4) suggests that, in choosing hosts, females of M. paulensis maximize the number of offspring per unit of search time rather than simply offspring quality.

Field collections of over-wintering and summer adults and nymphs of Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), Lygus borealis (Kelton), and Lygus elisus Van Duzee were made weekly in five fields in Saskatchewan in 1998 and 1999. The crops sampled were alfalfa, Medicago sativa L. (Leguminosae), canola, Brassica napus L. (Cruciferae), and mustard, Sinapis alba L. (Cruciferae), at Vonda, and alfalfa and canola at Saskatoon. In alfalfa, the most abundant Lygus spp. found in May and June were over-wintering adult L. lineolaris and (or) L. borealis; the predominant species in mid-June to early July was L. borealis; and the population from mid-July to late August was dominated by L. lineolaris. In canola, adult populations of Lygus spp. were not found until mid-June. The predominant species, L. lineolaris, probably over-wintering adults, was first detected in canola at the early bud stage in late June to early July; high numbers of L. lineolaris adults occurred in canola in mid-August. Populations of Lygus spp. in organic mustard were negligible. Dissections of field-collected Lygus spp. nymphs revealed parasitism in up to 70% of the midsummer population in alfalfa. In contrast, less than 1% of the late-season Lygus spp. population, primarily L. lineolaris in canola and L. lineolaris and L. borealis in alfalfa, was parasitized.

Over 250 durum wheats, Triticum durum Desf., and close relatives were screened for resistance to the wheat midge, Sitodiplosis mosellana (Géhin). Less than 2% showed consistently reduced egg and larval densities in field and laboratory trials. Two related accessions named ’Kahla’ had stable, low larval infestation levels, which were about 30% of those in commercial durum wheat cultivars. No antibiosis was detected in durum wheats. The reduction in infestation by larvae was associated with a similar reduction in oviposition. The resistance reduced egg densities by 80% or more in choice and no-choice laboratory tests and by about 70% in the field. Egg group size was not affected, and therefore reduced oviposition must have resulted from the number of egg groups deposited by females. The resistance was not associated with any of 12 morphological traits that were quantified for spikes. ’Kahla’ is the first durum wheat identified to have resistance against the wheat midge.