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For Trichodes, the elucidation of the life-history was a much simpler matter than for Systoechus. Trichodes had been bred out in the laboratory by Mr. Shiakides, Agricultural Superintendent in the Department of Agriculture at Nicosia, its larvae are easily identifiable and there is only one species involved. In the case of the Bombyliids, although the fully-grown larvae found in egg-pods were recognised as belonging to that family, yet no adults had been reared. There are several species of which the date of emergence and the adult life are more or less synchronised with those of Dociostaurus and which, moreover, are commoner on the locust sites than elsewhere. Three of these species appeared at first as possible predators: Thyridanthrax perspicillaris Loew, Exoprosopa telamon Loew and Systoechus autumnalis Pall.

Attempts to rear in the laboratory Bombyliids found as larvae in egg-pods in the field met with no success until the winter and spring of 1954, when they were induced to pupate after alternate wetting and drying of the soil in which they were kept. The adults that emerged first were from larvae collected in the soil in the vicinity of egg-pods during autumn sampling; twelve were Systoechus autumnalis and two were Thyridanthrax perspicillaris. Later emergences were from pupae derived from larvae taken from infested pods; eight adults were obtained and all were S. autumnalis. Examination of the large amount of preserved material available had already led to the belief that all the Bombyliid larvae found in egg-pods were of the same species, even though the species of this family are notoriously difficult to distinguish as larvae. It now appears probable that S. autumnalis is the only Bombyliid predator of Dociostaurus egg-pods in Cyprus.

Dempster (1957) lists a number of previous records of this species attacking egg-pods of other grasshoppers. It was also recorded as a predator of the Moroccan Locust in the Crimea by Stepanov (1882).

Until the various species concerned had been identified, field observations were made on the adults of all these possible predators; subsequent study was confined to S. autumnalis.

Systoechus autumnalis is rather widespread on locust sites in Cyprus but less is known about its distribution than about that of Trichodes. It has not been found where there are no locusts but it has been found where there are only a few. There is no evidence to suggest that it attacks other species of grasshoppers in Cyprus.

Both sexes are whitish and clear-winged. The males are readily distinguishable not only by the eyes, which are touching in the male and well separated in the female, but by the colour of the hairs on the thorax and abdomen which are silvery-white and more adpressed than in the female, giving them a shining, silky appearance. The hairs on the female are somewhat ochreous and more erect, so that the banding determined by their insertion on the abdominal segments is clearly seen.

Adults first emerge in May, soon after Dociostaurus becomes adult. The empty pupal cases can occasionally be found, projecting a little above the surface of bare, hard ground and split open at the top by the emerging fly. The adults fly actively, darting about with great rapidity. In ordinary flight, the wing-beats give a characteristic note and one is often aware that S. autumnalis is flying nearby without being able to see it. This sound is a useful guide to behaviour. When mating, the male and female fly around very rapidly and often the first indication of the mating flight is the markedly higher pitch of the flight note.

The adults show no attraction to locusts; they feed on the wing, sucking nectar from flowers (especially Compositae) and spend short intervals basking or resting either on flower heads or more usually on small twigs at ground level on or near the margins of bare ground.

The flies are found for about a month after their first appearance in May, after which they disappear from the sites. Until 1954, it was believed that this was the only period of adult life, but after the identification of the Bombyliid predator as S. autumnalis, autumn emergence was also looked for and was detected. In 1954, adults of the spring emergence were last seen at Mia Milea on 2nd June. During July and the beginning of August there were none on the site but on the 20th of August they were noticed at Pergamos, and on the 25th they were reported in some quantity on the upper site at Mia Milea. They were last seen there on 5th October. One-hourly collections were made at irregular intervals during these two periods, adult flies being sought within a defined area and caught with a net. The numbers captured at Mia Milea are shown graphically in Fig. 26. It will be seen that the numbers of adults on the site were much greater in the autumn than in the spring. Whether this is usually so is uncertain, though the higher percentage of locust egg-pods attacked in the autumn in other years and on other sites suggests that it is (see pp. 78, 80).

Fig. 26 - The numbers of Systoechus autumnalis caught in one-hourly collections at Mia Milea upper site, 1954.

The period of emergence is probably short. Ovary examinations show that when the first egg is mature, there are at least five more successive eggs at various stages of development in the paired ovaries. There is a variable number of ovarioles, approximately 300 ± 50 in all. Dissections throughout the season showed progressively fewer immature eggs remaining in the ovarioles, though there are no clearly defined and readily countable corpora lutea. Although the number of dissections was small (under 20) a reasonable estimate of the maximum number of eggs that could be laid by a single female would be of the order of 1,500. There were no specimens among the later dissections which contained immature ovaries, suggesting that the period of emergence is not a long one.

In some species of Bombyliid, the males are ephemeral. There is little evidence on this point for males of S. autumnalis, but it is probable that they are not. Males continued to occur in samples until the flies disappeared from the field and it is unlikely that they continued to emerge throughout this period while the females did not.

A certain amount of marking and releasing of adults was carried out in May, 1954, but they proved very difficult to mark adequately without damage. Few were marked and none ever recaptured; in all probability handling caused high mortality.

The principal food-plants of adults are, in the spring, mostly composites, such as Centaurea hyalolepis, Asteriscus aquaticus and Eryngium creticum, and in the autumn almost solely the very drought-resistant thistle Carlina corymbosa and Heliotropium villosum, the latter a species more common on cultivated than uncultivated land. There are, except very rarely, no other plants in flower on the sites at this season, and few elsewhere. All these species are annuals except Eryngium, which is a facultative perennial. Carlina germinates during the winter although it does not flower until late summer or autumn, and its abundance is affected by the distribution and amount of the winter rainfall; it is thus a precarious food supply.

Oviposition is on bare ground, often on the periphery of bare patches. The female hovers a few inches above the soil and with a flick of the abdomen throws the eggs one by one, with great accuracy, on to the selected spot. This is always in the shade, usually a small hole or tiny shadowy recess under a piece of litter, but females would sometimes come and lay into the shadow of the observer's hand while he was kneeling to watch them. A favourite spot is an abandoned trial bore-hole or an old empty locust egg-pod.

S. autumnalis will lay from one to nearly 20 eggs in one place then dart away to another, or rest for a moment or perhaps feed before beginning to lay again. During oviposition the flight note changes and is an excellent indicator of a laying female.

Many unsuccessful attempts were made to recover the eggs after oviposition had been observed, but the bulk of soil taken up for examination was always so large that no eggs or larvae could be distinguished. Eventually a number of small glass tubes were made, about the size and shape of an empty Dociostaurus egg-pod or trial bore-hole, and these were pressed into the ground flush with the soil, in bare areas frequented by S. autumnalis. After a time, females were seen to oviposit in them, and the number of flicks of the abdomen was recorded. In the laboratory the contents of the tubes were examined and the number of eggs was found to correspond with .the number of flicks. The eggs are therefore laid one at a time.

Once the appearance of the eggs was known, it was easier to obtain eggs laid in the soil. The eggs are slightly sticky when they are first laid and if they fall on loose earth they collect a film of particles which make them difficult to distinguish. In one old empty Dociostaurus egg-pod, 30 Systoechus eggs and three first-instar larvae were found. That these were indeed first-instar larvae was confirmed by a comparison with those obtained from eggs that hatched in the laboratory.

The eggs are smooth, white, unsculptured, and about 0.64 mm. by 0.36 mm. in size (Fig. 27). In the laboratory they hatched in dry Petri dishes on the open bench, in about 10-14 days. Towards the end of this period they could be induced to hatch by gently warming the Petri dish for a few minutes. It is possible that they hatch much more quickly than this in the field.

Fig. 27 - Systoechus autumnalis Pall. A, Eggs. B, first-instar larva, dorsal view. C, first-instar larva, lateral view of posterior segments showing pseudopodia. D, first-instar larva, abdominal segment showing pseudopodium extended and retracted. E, first-instar larva, anterior end.

The first-instar larva (Fig. 27) is a long, thin, transparent creature, 1.2 mm. long, actively running about from the moment of its emergence by means of its three pairs of thoracic bristles. It strongly resembles larvae figured by Porchinsky (1894, Systoechus sp.) and Paoli (1937). It possesses a large pair of maxillary palps provided with bristles, which it uses for digging as a mole uses its fore feet. It readily digs into loose soil. An attempt made to infest a Dociostaurus egg-pod was successful. On 21.ix.54, an egg-pod laid in the laboratory and therefore known to be free from predators was placed in a Petri dish with two such larvae and a little loose dry earth (largely to give a grip for the walking setae which skidded on a glass surface). Nine days later, the pod was opened and found to contain a second-instar larva, probably almost ready to moult; a similar larva is shown in Fig. 28.

Fig. 28 - Systoechus autumnalis Pall. A, second-instar larva, dorsal view (partially lateral view of thorax and head). B, third-instar larva, lateral view. C, another third-instar larva, anterior view.

The larvae will live, apparently without food, for about ten days in the laboratory. No interest in loose Dociostaurus eggs was shown by them, even several days after hatching.

After entering the pod by a minute hole the larva begins to feed. Considering its size and form it is improbable that it moults in the pod before feeding. There appear to be three larval instars (as in Cytherea obscura (Paoli, 1937) ). The instars are distinguishable as follows:

I. Minute, vermiform, transparent, active and free-living.

II. More or less cylindrical, slightly flattened, curved pearly white, inactive, feeding within the pod. Thorax not markedly of greater diameter than abdomen.

III. Flattened, markedly curved, yellowish inactive, feeding within the pod or lying in the soil. Thorax of greater diameter than abdomen.

The larva moves into the middle of the pod and ultimately to the base. The contents of the eggs are sucked out and the egg-shells pressed into a wad against which the larvae lie. Multiple infestation may occur but no more than three larvae have been found in a single pod. There appears to be no cannibalism. The occurrence of small second-instar and large third-instar larvae in pods collected in the autumn suggests that a single pod can suffer attack both in spring and autumn. Young Trichodes larvae have been found in the same pod as Bombyliid larvae in June samples, but not later, suggesting that the Trichodes larvae subsequently eat the Bombyliids.

After the first autumn rains, which usually fall in October or early November, the larvae abandon the pod, leaving by a single large hole in the basal wall, and live in the soil until the spring. Pupation does not take place until shortly before the adults appear in May. The pupal life is short, probably not more than a week. The pupae make their way to the surface and the adult flies emerge after the pupae have thrust about a third of the body above the surface of the soil. Some of the larvae remain in the soil until the autumn, when the second period of emergence begins. The remaining larvae probably retreat lower into the soil during the summer, below the depth to which the soil is usually dug in the course of sampling for egg-pods, for larvae are not usually found at this time of year. Isolated larvae have occasionally been found in small cells in the soil at a depth of three to four inches.

There is no evidence to suggest that the larvae remain more than one winter before pupating, although Künckel, according to Paoli (1937), believed that the larvae of Thyridanthrax fenestrata could pass three winters as such after leaving the pod.

A synopsis of the life-history is given in Table 38.

Table 38 Synopsis of the life-history of Systoechus

The two periods of emergence of adults can be regarded as a single one interrupted by the hottest months of the year. The biological advantage of a spring period of adult life is clear when it is considered how easily a dry year could result in the failure of the annual food-plants of the autumn period to develop. The evidence from egg-pod sampling shows that the larvae resulting from the spring attack do not generally complete their life-cycle in the autumn; that is to say, there is only one generation a year. Thus, in this respect S. autumnalis suffers from the same disadvantages as Trichodes as a check on the number of locusts. Since the autumn emergence takes place long after the adult locusts have died, there can at that time be no association between locusts and adult Systoechus. Nevertheless, the same type of place is chosen for oviposition by both Dociostaurus and S. autumnalis. Dempster (1957), from his studies at Mia Milea, concludes that there is a direct relation between the number of locust egg-pods and the number attacked by S. autumnalis, suggesting that the availability of egg-pods is more important in determining the size of the population of S. autumnalis than that of Trichodes.

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