Nocturnal Collections Research Articles

Mating Disruption of Mexican Rice Borers (Lepidoptera: Pyralidae) in Lower Rio Grande Valley Sugarcane

Mating disruption of Mexican rice borers, Eoreuma loftini (Dyar), by synthetic pheromone applications in sugarcane (Saccharum spp.) was investigated in large-scale field studies. Mating disruption was assessed using pheromone trapping, mating tables, stalk dissections, and nocturnal collections of adults. Pheromone traps were inappropriate for monitoring mating disruption. Mating tables supplied useful information but overestimated effects of pheromone applications on mating activities of feral rice borer populations. Adult collections and dissections supplied the least ambiguous assessment of mating activities, but were interpreted most easily in the presence of other substantiating data. Pheromone applications formulated in rubber ships or microporous beads and applied in a polybutene-based adhesive did not result in appreciable levels of mating disruption, and did not control rice borer populations or reduce associated stalk injury levels.

Abdominal angiostrongylosis in southern Brazil--prevalence and parasitic burden in mollusc intermediate hosts from eighteen endemic foci.

Angiostrongylus costaricensis is a parasitic nematode of rodents and molluscs are the intermediate hosts. Nocturnal collection of molluscs and search for infective third stage larvae of A. costaricensis was carried out in 18 endemic foci identified by the notification of a confirmed diagnosis in human biopsies or surgical specimens. Molluscs were digested in acidic solution and isolation of larvae eventually present was done in a Baermann funnel. Larvae identified by the presence of a delicate groove in the tail were counted to assess the individual parasitic burden. Four species were found infected, with ranges of prevalence in parenthesis: Phyllocaulis variegatus (7% to 33.3%); Bradybaena similaris (11.7% to 24.1%); Belocaulus angustipes (8.3%) and Phyllocaulis soleiformis (3.3% to 14.2%). Parasitic burden varied from 1 to 75 with P. variegatus, 1 to 98 with B. similaris. 1 to 13 with B. angustipes and 1 larvae in each of two specimens of P. solciformis. P. variegatus was present in all sites and was found infected with the highest prevalence figures and the highest individual parasitic burdens. These data stress the importance of veronicellid slugs as intermediate hosts for A. costaricensis in the endemic areas in Rio Grande do Sul, Brazil.

Mating Status of Tobacco Bud worm (Lepidoptera: Noctuidae) Males Captured in Pheromone Traps Compared with Males and Females Collected at Night by Hand

Mating status of males of the tobacco bud worm, Heliothis mrescens (F.), captured in pheromone traps was compared with that of males and females from nocturnal collections made by hand. The frequency of virgin males captured in traps before the mating period was similar seasonally and nightly to that of males collected by hand; thus, as far as mating status is concerned, males captured in traps appear to represent the insect population. However, pheromone traps did not capture males that had emerged or mated previously the same night. The frequency of virgin males decreased during the night but increased with season for both those collected by hand and in traps. The frequency of virgin males from trap capture cycled with peak frequencies occurring at the beginning of a population peak as determined by numbers of males trapped. Based upon the linear relationship between numbers of sperm bundles within the duplex and time, the average weekly age of virgin males also cycled over the duration of the study, ranging from 1 to 4 d. The oldest virgin males were trapped in the spring, just before the first population peak, which may indicate a spring inl:luxof moths.

Survey of Adult Mosquitoes (Diptera: Culicidae) During Irrigation Development in the Mahaweli Project, Sri Lanka

A survey of adult mosquitoes was done during 1986-1987 in an area undergoing irrigation development in the Mahaweli Project of Sri Lanka. The study encompassed two 12-mo phases of settlement and irrigation, respectively. Diurnal human bait catches yielded 1,427 female mosquitoes in 27 species. Nocturnal collections (human bait, CDC light traps, indoor resting catches) produced a total of 30,491 females in 67 species. Comparisons with an earlier survey in the predevelopment forest showed that the diurnal human biting abundance of Aedes albopictus (Skuse) remained stable, whereas the abundance of Ae. novalbopictus Barraud and Ae. w-albus Theobald declined drastically after development. Man-mosquito contact increased substantially for nocturnally active Anopheles annularis van der Wulp, An. subpictus Grassi, Mansonia uniformis (Theobald), Culex tritaeniorhynchus Giles, and Cx. quinefasciatus Say and decreased for Ma. annulifera (Theobald) and Cx. gelidus Theobald. A small increase occurred in An. culicifacies Giles, An. vagus Donitz, An. varuna lyengar, Cx. fuscocephala Theobald, and Cx. whitmorei (Giles); Cx. pseudovishnui Colless decreased. The effect of changes in mosquito abundance on the increased transmission of malaria and Japanese encephalitis is discussed.

A new type of collapsible insect-surveillance light trap for sampling Diptera.

The newly designed Army Collapsible Insect Surveillance trap for nocturnal collection of flying Diptera that are attracted by light is described. A polyvinyl chloride construction increases durability, while the capability to collapse from a height of 92.1 cm to 24.1 cm facilitates transportation and storage.

Age structure and survivorship of Culicoides variipennis (Diptera: Ceratopogonidae) in central New York State, USA.

Studies were conducted adjacent to a farm pond in central New York, USA, over 2 seasons to determine survivorship and to assess the vector potential of female Culicoides variipennis (Diptera: Ceratopogonidae). Many nullipars and some pars attacked man during the day near the habitat. Most adults collected nocturnally or at dawn by CO2-baited light trap were parous and had oviposited within the previous 12 h. Seasonal parity fluctuations were unreliable indicators of voltinism, since nullipars apparently were poorly represented in crepuscular and nocturnal trap collections. Parity rates and numbers collected varied with time of collection and animal access to the area. Some females lived to complete 4 gonotrophic cycles and were estimated to be a minimum of 19 days old. Stage survivorship decreased with age and was calculated at 0.327, 0.148, and 0.167 for unipars, bipars, and tripars, respectively. Mean parous rates (nulliparous stage survivorship) were 0.61–0.65 but were probably exaggerated owing to the undersampling of nullipars. Theoretically, survivorship was apparently sufficient to allow bluetongue virus transmission at this site, providing other factors (e.g., biting intensity on ruminants and transmission rates in vector populations) were favorable.

Estimating dietary sodium intake in individuals receiving a randomly fluctuating intake.

Previous investigations examining techniques to estimate sodium intake in free-living persons failed to consider a varying intake or were not conducted under circumstances in which the intake was actually known. To examine the utility of 24-hour and nocturnal urine collections as estimation of sodium intake under such conditions, we studied 43 white and black men and women ingesting a known sodium intake for 10 days that was randomly varied daily, with a mean intake of 150 mEq/day + 2 SD (range, 50 to 250 mEq/day). The mean 24-hour sodium excretion (UNaV) per day was and 24-hour UNaV estimated that day's sodium intake accurately for the entire 10 days, the average of several 24-hour collections was required. Nine collections were optimal (r = 0.75). Nocturnal specimens were not helpful; the average of all 10 collections correlated weakly (r = 0.30) with sodium intake. These data suggest that to estimate mean sodium intake accurately in free-living persons, only 24-hour collections are useful, although nocturnal collections are helpful in evaluating compliance with low sodium intake.