Bull. Org. mond. Santa 91 4-6 Bull.BullWorldo;tdHlthHithi Org.rg }1951, 4, 547-562 AN EXPERIMENT IN TRAPPING AND CONTROLLING ANOPHELES MACULIPENNIS IN NORTH IRAN C. GARRETT-JONES, M.Sc. Entomologist, World Health Organization Manuscript received in April 1951 Page 1. Kalardasht valley . 547 2. Method of work . 548 3. Anopheline fauna . 551 4. Malaria incidence . ... 552 5. Bionomics of the trapped mosquitos . 552 6. Results of residual-spray treatments . 556 Summary 560 Resume5 In July 1950 the authorities responsible for malaria control in Iran wanted field tests carried out to show the effect of indoor residual DDT, in various forms, on the local malaria vectors. For this purpose, the insecticide was applied in a few villages lying in the valley of Kalardasht, in the Elburz Mountains. Four forms of the insecticide, in two concentra- tions, were used in neighbouring villages during August. The effect of each was assessed by attaching outlet traps to rooms and stables in ordinary use. This technique, which appears to have been but little used in studying the Anopheles maculipennis complex, also yielded some information about its endophilic habits in the locality. 1. Kalardasht Valley The Kalardasht Valley (51015'E., 36030'N.) lies on the northern slopes of the Elburz mountain range, about 20 miles (32 km) south-west of the town of Chalus on the Caspian coast. It contains a roughly triangular plain, sloping from 4,500 feet (1,370 m) to 3,000 feet (900 m) above sea- level. The plain is about six miles (9.7 km) across. The Chalus river, a large, rapid stream, runs through it, much of its water being diverted at the upper part to irrigate the corn and millet fields, and some finding its 97 - 547 - 548 C. GARRETT-JONES way back in the lower part. In addition, the stream is fed by several tributary springs in the valley, with which small swamps are associated. FIG. 1. OUTLET TRAP FOR MOSQUITOS AT No statistics of the rainfall ISFANKALEH,IRAN at Kalardasht are available, but it exceeds 40 inches (102 cm). There is no pronounced dry season. During August, two days in three were cloudy and there was a good deal of drizzle and damp mist, the I E illclouds from the north-west lying low over the plain, or sometimes upon it. Day and _ night temperatures were mild. The first light fall of snow came in the last days of ............October. Kalardasht has 25 villages j~~~~ with an average population I.. of 250-300. Most are situated ....on the hills round the plain. Two of those on the plain itself are large (over 1,000 people each), but four others are among the smallest, having only four to swix houses. This was said to be due to malaria, sometimes on thecoastalplainamongtherice-fieandthe spleen-rates in those replaces indicated hyperendem- The writer spent four weeks aticity. The villagers are mainly sedentary, but there is a small amount of winter migration down to Chalus. In summer whole families walk down to that town on market days, and may pass the night sometimes on the coastal plain, among the rice-fields which cover it. No rice is grown at Kalardasht. 2. Method of Work The writer spent four weeks at.Kalardasht and had the assistance of three student-technicians who functioned as mosquito- and water-surveyors and collected the mosquitos from the outlet traps. One of them remained for a further two months to continue the trap collections and to make periodic collections of larvae. For parts of August the services of ANOPHELES MACULIPENNIS IN NORTH IRAN 549 an FIG. 2. OUTLET TRAP FOR MOSQUITOS ON Iranian malariologist, an WEST WALL, ABISHDONI, IRAN experienced spray-team, and two engineers were provided. Sixteen villages, with child spleen-rates ranging from 83 to 27%, were treated in the ten days of August when | the spray-team was available. The insecticides used were technical DDT powder 5 % solution in kerosene (five vil- lages), DDT 75% wettable powder in water suspension (seven villages), DDT 50% wettable powder in water sus- pension (three villages), and "DDTane" 50% wettable paste in water suspension (one village). All these were applied to leave 2 g of DDT per m2 of treated surface, ex- cept in two villages where the 75% powder-suspension was applied at a rate of only 1 g per M2. The aim was to treat all the inside walls and ceilings in a village, except for an un- Window opening, carrying inlet valve, is seen treated control room. beside the trap. The outlet traps (see fig. 1 and 2) were not of uniform size, but the principle was the same in all of them. They were rather large traps of dimensions up to 36 inches x 30 inches x 15 inches (91.4 cm x 76.2 cm x 38.1 cm), made of muslin sewn or glued over a wooden frame. The side of the trap placed against the window opening had a one-way horizontal slit entrance in its upper half, the slit directed upwards so that a mosquito flying towards the sky would enter by it. The muslin surfaces above and below the slit were inclined like the two arms of the figure 7, the slit being at the angle. The traps were not detachable, but were fixed in position for the duration of the tests. The mosquitos were collected from them morning and night through sleeves in the traps, by means of aspirator-tubes and test-tubes. The method was very laborious (in the more successful of the traps), and did not permit the traps to be used as laboratory cages for observing the 24-hour death-rate. The rooms remained in normal use by their inhabi- tants throughout the tests. 550 C. GARRETr-JONES Each room carrying an outlet trap was fitted also with an improvised inlet valve (see fig. 3) in the shape of a triangular pyramid with an edge of 24 inches (61 cm). The open base was applied to the inside of a second window opening (visible beside the trap in fig. 2), and there was a small upwardly directed hole at the apex, by which the mosquitos could enter the room. It was hoped that mosquitos seeking to leave by this route FIG. 3. HOME-MADE INLET VALVE APPLIED TO WINDOW OPENING f hq: . Held in position by one drawing-pin. would fly against the inwardly sloping muslin sides of the valve, but would not find their way downwards through the apical hole. It is not known whether these valves prevented some mosquitos from entering the rooms, nor whether some succeeded in getting out by them. Where the rooms have not open eaves, so that an inlet valve is desirable, it would probably be better to make it of plywood in order to minimize the amount of light and air passing through it. During the months August to October the ten outlet traps at Kalardasht (nine of them fixed in villages which had been sprayed near the start) were successful in trapping over 2,700 mosquitos. It is worth noting that the trap at Abishdoni (fig. 2), which caught by far the largest number, was fixed on a west wall. This does not confirm the view that outlet traps should have an easterly aspect and catch the first light of day. An incoming air current may play a part in directing mosquitos towards the trap. Further- more, traps which are to serve as cages should be provided with one solid ANOPHELES MACULIPENNIS IN NORTH IRAN 551 angle in which mosquitos may shelter from the sun and wind; this was not done at Kalardasht. Owing, likewise, to limited resources, it was not possible to carry out mosquito dissections or blood-precipitin tests. 3. Anopheline Fauna Anopheles claviger Mg. in aquatic stages occurred commonly in small marshes and the shady parts of streams, often in company with A. maculi- pennis. No adult A. claviger was taken resting indoors, but adults were found commonly in the vegetation shading one of its breeding-places. This accords with what is known of the species on the Caspian coastal plain, where it is found in indoor resting-places during the spring and autumn only. Further, the trap catches showed that it was very rare for this species to enter houses by night. A. plumbeus Ste. was common in holes in the Fagus trees of the surrounding forest. One female was identified from the outlet trap at Taluchal, a village in the plain, more than a mile from the nearest forest. This village, like others, contains no trees except a few large walnuts. A. hyrcanus Pall.: two or three specimens were taken in the traps at Vohai. The larvae were found in a stagnant, overgrown pool of somewhat polluted water in the same village, together with eggs of A. maculipennis maculi- pennis. A. hyrcanus is also common nearer the coast (where I have found it breeding in fresh-water seepage pools on the Caspian shore) and, like A. claviger, it is found indoors more often in spring than in summer. A. maculipennis maculipennis Mg.: this appeared to be the only member of the maculipennis group present at Kalardasht. All the specimens trapped will be considered as a single population, because some 30 batches of eggs collected and 18 other batches laid in captivity were all of the same type. This mosquito was by far the most prevalent Kalardasht species. Throughout the plain, the larvae were found in irrigation seepage swamps, ditches, and marshy stream margins, and in even greater numbers in still pools, where the water was clean.