The device sold by ISOTRONIC consists of a blue hard plastic case measuring approx. 6 cm x 2 cm (2 3f8 “ x 3)4 “ ( without the plug pins) and is designed for direct introduction into a power outlet (220 V or 110V AC); its upper side (front side in the plugged-in state) features a cover plate provided with three slots. By the manufacturer it is said • see the enclosed description of the original packaging – that the device generates an „ultrahigh sound“ which matches with the vibrations (wing beats per second) of male mosquitoes and stops the female mosquitoes from biting. The description says, among other things: „ULTRA ANTI INSECT emits an ultra-high sound that is hardly audible for the human ear. It cannot, however, be missed by a female insect. The female thinks to hear the noise of a male insect. It therefore takes to its wings because it has already been fecundated.“
Thus, the device operates without use of chemical additives of any kind – exclusively on the basis of physical phenomena.
The following steps were taken to test the device:
Using a net, larvae of the common mosquito, also known as the common house mosquito and being of the genus culex pipiens of worldwide propagation, were taken from ponds, brought to the laboratory and put into aquariums that were covered with fly gauze.
After pupation of the larvae, which took just a few days (at approx. 22 ° to 25 * C this takes up to 10 days), the imagoes (sexually mature insects) hatched after another two days of pupal rest.
The freshly hatched imagoes gathered below the gauze covering. To feed them, cotton swabs soaked with sugared water were placed upon the gauze so that the mosquitoes were able to feed on the sugared water from below and through the gauze.
For the experiments the mosquitoes were set free in a closed room and counted to establish their magnitude.
For the first experiment about 200 mosquitoes of both sexes and about one day old were used, so that a minimum of 80 female insects can be assumed. Since only the female mosquitoes are sucking blood, while the males feed exclusively on the saps of the plants, only the number of female insects is of consequence for the molestation caused or not caused to humans. Since the description of the device indicates that only fertilized females are bloodsuckers, the male insects were left in the experiment to assure fecundation in case this should not have taken place in the breeding tanks.
(The question of fecundation is of minor importance for all practical uses of the device because all female insects caught outdoors are fecundated. Eichlar, W.: Fundamentals of veterinary entomology VEB G. Fischar, Jena 1980, writes on page 44: „The male insects gather in swarms above elevated spots (such as a shrub, their buning sound (and smell?! attracting the females, which enter the swarm for mating with the males. Mating is followed (on the part of the female insects only) by the sucking of blood and then (after the eggs have maturated! by the eggs being discharged upon the surface of a body of water… „.!
Even if mating had not occurred inside the enclosed space, this should not affect what is being said about the result, because insects of the genus anopheles maculipennis. for example – and this is likely to hold true for other genera as well – tend to suck blood without having mated. Martinti, E.: Textbook of medical entomology, G. Fischer, Jena, 1952, writes on page 194: „Whether the females have sucked blood before or after mating is without consequence for the hatchability of the eggs „ and on page 191: „the mosquitos are more or less eager to bite right after hatching“. These statements make it clear that at least a number of culcidae genera tend to suck blood without having been fecundated, this being a fact that is likely to increase the uses of the ULTRA ANTI INSECT.
Results of the experiments:
The ULTRA ANTI INSECT device was tested in July 1989 in a room measuring 5.1 x 2.7m-13.8 square meters (approx. 150 sq.ft.). The room had a height of 2.7 m, making it a cubic volume of approx. 37 m ‚ (1300 cu ft.). Since the description says that only one device is needed for rooms measuring from 20 to 25 m‘ (200 to 270 sq.ft.), only one device was used.
The device was plugged into a power outlet in one of the narrow walls of the room, next to the door and opposite the window, the bed of the female test person, aged 27, was placed at a distance of about 1.5 m (5 ft.) from the device. This was done a) to simulate the usual conditions in bedrooms and was necessary b) to avoid perceiving the „ultra-high“ sound that the test person heard when very close to the device.
As mentioned before, approx. 200 mosquitoes of both sexes and about one day old were set free in the room after having been fed with sugared water. The temperature inside the room was about 25 ° C and the humidity of the air was brought to a level, by suspending wet pieces of cloth, assuring an optimum climate for the mosquitoes. No light was burning inside the room, the window was closed.
During the first night of the experiment the device was operating continuously. The test person was able to clearly distinguish the mosquitoes filling the air thanks to the differing sound of the two sexes. In spite of the large number of female mosquitoes (at least 80) no mosquito has settled on the test person to suck blood during the first night from about 11 p.m. to 7.00 a.m..
When the light inside the room was briefly switched on several tines, most of the mosquitoes were seen to have settled on the walls farthest away from the device, a number of mosquitoes were sitting on the wall into which the device had been plugged. This seems to suggest that there could be some kind of „silent zone“ behind the device, between the wall and the back of the device (approx. 2.5 cm-1″).
The same mosquitoes were used for the second night and the fact that these mosquitoes due to their age (at least two days old) would demonstrate an even greater activity to suck blood was consciously taken into account. Initially, the experimental conditions were identical with those of the preceding night, but were then varied by switching off the device after about two hours and, subsequently, continuing the experiment with the device in operation and the window being tilled.
While during the first phase – device operating • the result corresponded to that of the proceeding night, the mosquitoes started to become active after the device was switched off. The molestations started after only a short period of time and resulted in several bites in spite of attempts to fend off, with the hands, the mosquitoes that were approaching in the dark. This second phase of the experiment was therefore shortened – it lasted only for about 30 minutes • to switch to the third phase.
The operating device was effective almost immediately, and in the course of the next few hours a large number of mosquitoes had escaped through the „tilted“ window.
To test the possible influence of the mosquitoes‘ age upon their aggressiveness, a further experiment was conducted with mosquitoes that were up to seven days old; during the intervening „waiting phase“ they had been fed with sugared water.
The experiment was conducted in the same manner. In the evening approx. 250 mosquitoes were set free in the room accommodating the test person.
With the device in operation the results were as convincing as with the preceding experiments with younger mosquitoes. There occurred no bites. After the device was switched off, however, the aggressiveness or biting activity was clearly higher as compared with the younger mosquitoes so that this experimental phase was limited to a few minutes (about 15 min.).
After the experiment and with the device operating, the mosquitoes were again given a chance to escape through a „tilted“ window. The result was identical; by next morning most of the mosquitoes had left the room without any molestation occurring in the intervening time.
To sum things up it can be said that in a moderate climate and with the most common genus of mosquito • culex pipiens – the ULTRA ANTI INSECT device does what is being claimed on the package, that the desired effect is really being achieved.
The statements made are true of the culicidae used for the experiments predominantly of the genus culex pipiens which is also called the „common mosquito“ or „house mosquito“ and which in European climates is among the worst „pests“. It is also a widespread cosmopolitan insect but in other climatic zones other genera tend to play an important or even medically significant role such as the malaria vectors of the anopheles genus.
Since we know approx. 2,400 species of the culicidae family of which about 80 have been proved to exist in Europe and about 40 alone in Germany, partly with differences in their biology, behaviour, etc., in genus or another may possibly not be affected by the „ultra-high sound“ in the same manner. As the rapid wingbeats that produce the buzzing sound of the mosquitoes – 330 per second for the males and 220 per second for the females of the anopheles maculipennis genus – are only known for individual species but will certainly differ within wide limits, the reaction of the mosquitoes to a constant ‚ultra-high sound“ is bound to differ as well.
However, these remarks are not meant as a negative assessment of the ULTRA ANTI INSECT device but only as an observation that in one case or another the device may possibly fail to produce the desired effect in full. This is nothing that speaks against the effectiveness but something that implies that in such case species of mosquitoes demonstrating a different reactive behaviour take part in the aggression.
The enormous number of species precludes any possibility of including all culicidae commonly found in a certain region in an investigation of the effective range of the ULTRA ANTI INSECT device.
If the concerns mentioned in the last place should prove correct in practical use one could possibly think of producing devices emitting sounds of different pitch to use them in areas where mosquitoes perceiving different frequencies of sound are common.
To what extent the devices can be used in rooms in which dogs are staying would require separate test inasmuch as it is known that dogs have a marked faculty of hearing very high sounds and could possibly be much irritated by the „ultrahigh sounds“ of the ULTRA ANTI INSECT device.
Prof. Dr. W. Frank
