This paper reviews information on quantitative aspects of filaria larval populations in the mosquito phase. One aim is to clarify the conditions necessary for efficient filarial transmission by mosquitoes during maintenance in the laboratory, including the requirement of suitable microfilaraemia in the host animal. Secondly, attention is given to ways of analysing the dynamics of filaria transmission in endemic areas. In general, the rate of mosquitoes becoming infected with microfilariae is proportional to the density of microfilaraemia in the host; the actual numbers of microfilariae ingested also increase in proportion to the microfilaria density. Numbers of ingested microfilariae may not be as expected from theoretical calcaulations based on two parameters : "microfilaria density in the host" and "quantity of blood ingested by mosquito." Some papers have reported mosquitoes to ingest fewer or more microfilariae than expected on the basis of these parameters. However, other studies have found that the mean number of ingested microfilariae is more or less close to what would be expected. Some possible explanations are discussed in order to account for the observed variations in the numbers of microfilariae ingested by mosquitoes. Such differences have been found between mosquito species, between strains within the same species, and between mosquitoes of different ages. Microfilaria intake is not so well correlated with the quantity of blood ingested. Defecation or discharge of blood from the anus of engorged mosquitoes may affect the number of microfilariae ingested and retained. In some species of mosquitoes oesophageal armatures may kill some of the ingested microfilariae. Density variations of microfilariae in different regions of the host skin must also be monitored carefully in relation to the feeding-sites of female mosquitoes. Several authors have shown that only limited numbers of filarial larvae develop to the third (infective) stage in each mosquito, despite the ingestion of more microfilariae by some individual female mosquitoes. Two basic factors are considered to account for the failure of some microfilariae to grow successfully. Either the infected mosquitoes may die, or else there may be mortality of the filarial larvae themselves. Under laboratory conditions, it seems that mosquito mortality is the greater influence. Additionally, some of the infective larvae may fail to be transmitted when the vector feeds again on a vertebrate host. This is due partly to third stage larvae remaining within the mosquito, and partly to failure to penetrate the host's skin by those infective larvae which escape successfully from the vector. On the basis of papers quoted here, it is suspected that in endemic areas the parasite yield is less than 10% of the total microfilariae ingested, with a few exceptions such as Brugian filariae ingested by Mansonia mosquitoes. This reduction of parasite yield is largely due to the mortality of mosquitoes during the incubation period for filarial larvae. Mosquito longevity, whether or not specimens have become infected with filariae, is therefore a most important component of vector capacity under field conditions. Transmission efficiency is expressed in terms of several indices, proposed and discussed here. For continuing epidemiological surveillance of filariasis, it is considered necessary to minimize the number of factors to be observed for measurement of transmission efficiency, in order to economize the use of man-power and technical resources for field operations.

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Hybomitra tsushimaensis, a new species, was described based on the materials collected in larval and pupal stages, from Tsushima Islands. This species is quite allied to H. borealis (Fabricius) in size and color, but differs from it in the more elongate middle callus of the frons and undarkened palpi in female.

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An aggregation pheromone was demonstrated in an acarid mite, Lardoglyphus konoi. This aggregation pheromone was extracted and isolated from the mite. The active compound was found to function as the aggregation pheromone not only in con-species but also in other three related species of mites, Carpoglyphus lactis, Aleuroglyphus ovatus, and Tyrophagus putrescentiae.

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Two mutants, hairless-antenna (ha) and white-eye (w), in Aedes togoi had been previously reported to be located on the same side of the pigmented pupa (p) locus in linkage group 2,but the gene sequence of these three alleles had not been determined by the three-point experiments. This study confirmed that the gene sequence is p-ha-w, and showed that the recombination units between p and ha range from 11.9 to 38.4 and the units between ha and ω are more than 32.4. A new mutant, extra-jointed palp (Ex) is the first dominant mutant described in Aedes togoi. The Ex allele exhibited very low penetrance of 34% and was found to be located over 32.5 map units far from the ru (ruby-eye) locus in linkage group 2. The Ex trait is sex-limited, expressed in only female palps; in the Ex female there is an additional segment extended from a normal palp. This extra segment is pointed and covered with white scales instead of black ones.

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The affinity of Simulium metallicum for Onchocerca volvulus was compared with that of a good intermediate host, S. ochraceum, by maintaining infected flies under 25±0.5℃. The larval development in S. ochraceum was synchronous, but that in S. metallicum was asynchronous and malformed, stunted larvae often appeared. The results suggested that the ability for S. metallicum to transmit O. volvulus would come to about 1/3.5-1/5 of that of S. ochraceum. Some information about the affinity of S. horacioi Okazawa and Onishi, 1980 for O. volvulus that closely resembles S. metallicum was given.

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In this paper, the author described and redescribed the 3rd instar larvae of 3 species belonging to the genus Scatophaga Meigen, namely S. scybalaria (Linne), S. stercoraria (Linne) and S. suilla (Fabricius), and presented a key to the species from Hokkaido.

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Using young and old mosquitos (5 days and 12 days after emergence), we measured the following parameters : 1) blood meal size, 2) number of microfilariae ingested, 3) number of worms migrated from the midgut in 2 hr post feeding, 4) survival rate of mosquitos and 5) number of mature larvae in the mosquitos 14 days after ingestion of microfilariae. In young mosquitos the first three parameters were higher than for older ones; the survival rate of infected young mosquitos was less than for uninfected ones. At 14 days after ingestion, the infective rate and mature larva rate of the young mosquitos were less than for the older ones, but the total number of mature larvae dissected from young mosquitos was higher. The number of microfilariae ingested was less than the value expected from the density in the host blood. The correlation coefficient between the blood volume and microfilariae ingested was calculated as 0.5,which was not statistically significant.

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Blood meal sources of field-caught engorged mosquitoes were identified by agar gel diffusion. Mosquitoes were collected in a paddy area on the outskirts of Sendai, northern Japan in 1968 and 1969. Various sampling techniques were used for collecting engorged mosquitoes; Kato's animal baited traps installed at the two pig sheds were operated at night, while a suction catcher, a drop-net cage and a sweepnet were employed in the daytime. Of Culex tritaeniorhynchus, two kinds of blood-fed samples were collected; one contained some partial feeders trapped while flying from one host to another at night, and the other consisted of fully engorged mosquitoes resting in the daytime. Blood meal sources of the former were in most cases mammals, pigs making up more than 70% of the total identified. This feeding pattern did not change between the earlier- and the later half of the night. The daytimeresting Cx. tritaeniorhynchus also fed principally on pigs and cows both in 1968 and 1969. These results show an ecological basis for the pig-Cx. tritaeniorhynchus cycle of Japanese encephalitis virus during the epidemic season in Japan. Anopheles sinensis fed on pigs and cows, while Cx. pipiens pallens was characterized by a wider range of hosts and fed mainly on birds.

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Blood meal sources of Culex pipiens pallens collected in the field during the daytime were serologically identified by the Ouchterlony method. Mosquito collections were made at two stations in two areas 4km apart from each other in the suburbs of Kyoto in 1973 and 1974 by using a drop-net cage and sweeping. Blood removed from the engorged mosquito was tested against ten kinds of antisera. Eight different hosts identified were mammals to reptiles, i. e., bird, dog, cat, cow, pig, mouse, snake and human, showing that the blood meal sources of this mosquito were not restricted to a particular host, but covered a variety of animals. Feedings on birds and dogs made up the greater part of the total identified at the two stations, but the ratio of bird-feeding : dog-feeding differed between the stations suggesting that the host selectivity by this mosquito might vary depending on the availability of host animals.

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Bethylid wasps, Cephalonomia gallicola, were found parasitizing on ca. 28% of anobiid beetles, Stegobium paniceum, occurred in stored oil cakes in Nagoya in 1976. The most frequent site of the parasitism was the ventral abdominal surface of the beetle larvae. With a colony propagated in the laboratory, observed were the following habits of the wasps : 1. The wasps propagated themselves during the period from February to October. The propagation seemed to be most vigorous during July to September. 2. Female wasps oviposited more frequently on the beetle larvae in cocoons. Number of wasp larvae hatched from the cocoonless beetle larvae was ca. 1/5 of that from the larvae in the cocoons. 3. Total developmental period of time of the wasp was about 60 days in the springtime, but 20 to 30 days in the summertime. 4. Hibernated wasp females survived for 60 to 180 days, but males, having mated repeatedly in a short time after emergence, survived less than 10 days. The mating time of the wasps was ca. 2 min in an average. 5. Female wasps were observed, besides ovipositing on the beetle larvae, to kill and consume these larvae. 6. Experimentally, larvae of a ptinid beetles, Gibbium psyllioides, were parasitized by the female wasps.

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We examined the new method for measuring the amount of blood meal in individual mosquitoes using a spectrophotometric technique and the number of microfilariae by membrane filtration method. Aedes togoi were fed on jird parasitized with Brugia malayi and frozen at -20℃ immediately. The midgut containing blood meal was homogenized in 2ml Drabkin's solution [1.0g NaHCO_3,0.1g K_2CO_3,0.05g KCN, 0.2g K_3Fe (CN)_6,in 1 liter distilled water], and incubated at room temperature (20-25℃) for 30min. The homogenate was filtered through Membrane filter (pore size=3μm). The filtrate was transferred to a microcuvette and the optical absorbance was read in a spectrophotometer at 540nm. The blood volume was calculated from the relationship between blood volume and optical absorbance calibrated previously. The homogenizer was washed with 4ml distilled water and the water was filtered through the same membrane to collect the suspected remainder of microfilariae. Then, the membrane was transferred on a glass slide and stained with 0.05% Azur II solution. The number of microfilariae was counted under a microscope. The contamination of Malpighian tubule caused the increase of optical absorbance equal to 0.4 μl blood. The homogenized sample was stable for 2hr and the suitable clearance of homogenizer was 0.2mm in this case.

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