Cyrtogaster vulgaris Walker, a pupal parasite of the alfalfa blotch leafminer, Agromyza frontella (Rondani), acts as a secondary agent as well. The adults, which deposit their eggs within host puparia, apparently do not discriminate between healthy leafminers and those parasitized by Dacnusa dryas (Nixon). The egg and larval cephalic structures of C. vulgaris are described and illustrated and the final-instar larval skins of the two parasite species are compared.

Two field experiments were conducted to determine if Orthotomicus caelatus (Eichhoff) was attracted to pine bolts infested with conspecifics and to assess the roles of the sexes in attraction. Traps baited with pine bolts artificially infested with males attracted both males and females, but traps baited with uninfested bolts or bolts with females caught very low numbers of beetles. The addition of females to bolts with males reduced the attraction produced by males in a second experiment. Bolts with males and females did not reduce the attraction produced by other males in adjacent bolts, suggesting that females do not produce a masking pheromone. The pheromone system of O. caelatus is similar to those known for other species in the Ipini in which males initiate gallery construction, produce an attractant, and attract females and opportunistic males. Preliminary gas chromatographic analyses of extracts of hindguts and frass from males boring on pine bolts suggested the presence of ipsdienol and ipsenol, two commonly occurring pheromones in other species of the Ipini. The pheromone system of O. caelatus is discussed with regard to the complexity of the pine bark beetle guild in the southeastern United States.

Spatial and temporal variability are essential considerations in the study of aquatic insects. Traditionally, these two sources of variability are treated separately; however, they should be considered together because they occur concurrently in natural systems. To illustrate this interaction, we constructed two-way variability tables in which spatial (habitat, reach or zone, system, intersystem) and temporal (within a day, within a season, within a year, year to year) scales were ordered on separate axes, and examples of concurrent spatial and temporal variability were entered at the intersects of the scales. We examined three aspects of aquatic insect life histories in lotic and lentic waters using such tables: emergence, feeding and growth, and movements and migrations. It proved easier to find examples for the stream tables than for the lake tables, perhaps because of greater spatial and temporal variability in lotic than lentic waters. Also, more papers have been published on stream than on lake insects over the last decade or so. Spatial and temporal scales at which lotic and lentic research is done were determined by examining the recent contents of five key aquatic journals (≈ 500 articles). Research on aquatic insects appears generally to be done at relatively long temporal scales, but at smaller spatial and shorter temporal scales in lotic than lentic systems. Perusal of the literature to find examples of concurrent spatial and temporal variability revealed the prevalence of a “mean-values” appproach to data analysis, in which investigators “homogenize” data to reduce spatial and temporal variability. However, it is this spatial and temporal variability that often provides an explanation of factors causing the patterns observed. A “variance” approach, in which data are disaggregated and fluctuations or extremes are considered, may be far more informative and may elucidate underlying mechanisms.

The North American species of Momonia Halbert, 1906, are revised. Larvae, deutonymphs, and adults of Momonia campylotibia sp.nov. are described, adults of Momonia marciae Habeeb and Momonia projecta Cook are redescribed, and deutonymphs of M. projecta are described for the first time. New morphological, life history, and distributional data are presented for all species. A new diagnosis of Momonia is proposed, and a key to adults of all known species of the genus is included.

Morphological, life history, and distributional data are presented for North American species of the subgenus Allomomonia Cook, 1968. Adults of Stygomomonia (Allomomonia) moodyi Mitchell are redescribed, and deutonymphs and adults of four new species, S. (A.) pacifica, S. (A.) mendocinoensis, S. (A.) mitchelli, and S. (A.) atnarkicola, are described for the first time. Larvae tentatively identified as S. (A.) mitchelli are also described, and host associations of these, and larvae that appear to belong to other species of Stygomomonia, are presented and discussed. New distributional data are presented for all species. A new diagnosis of Allomomonia is proposed, two new species groups, the moodyi and mitchelli groups, are proposed and diagnosed, and a key to adults of North American species of the subgenus is included.

The sweetpotato whitefly, Bemisia tabaci (Gennadius), was accidentally imported into Canada on poinsettia, Euphorbia pulcherrima Willd., cuttings from the United States in 1987 and in 1988. The biology and population dynamics of B. tabaci were reviewed by Butler et al. (1986). It is a worldwide pest of more than 500 plant species in 74 families. Prior to 1986, there was only one report of this insect as a greenhouse pest, on vegetables in Turkey (Lopez-Avila and Cock 1986). Bemisia tabaci was first reported on poinsettia in Florida greenhouses in November 1986 (Price et al. 1987). In 1987, this insect was reported as a pest on field tomatoes in Florida (Schuster and Price 1987).