First Morpho-Functional Assessment of Immature Stages of Pelecocera Species (Diptera: Syrphidae) Feeding on False Truffles.

With 14 species, Pelecocera Meigen, 1822 is a scarce and small genus of hoverflies (Diptera: Syrphidae: Rhingiini) from the Holarctic Region. Apart from the finding of larvae of Pelecocera (Chamaesyrphus) japonica (Shiraki, 1956) in fungi in Japan, the larval biology of these hoverflies is virtually unknown. The early stages of all Pelecocera species are undescribed. The adults of Pelecocera (Pelecocera) tricincta Meigen, 1822 and Pelecocera (Chamaesyrphus) lugubris Perris, 1839 are found in Palearctic conifer forests with sand dunes. We here report the first morphological evidence of the immature stages of Pelecocera (P. lugubris and P. tricincta), as well as specific data on their breeding sites. Larvae of both species were collected feeding on the hypogean basidiomycete Rhizopogon luteolus Fr. & Nordholm, 1817 in Denmark in 2021. The first larval stage and second larval stage of P. tricincta, the third larval stage of P. lugubris, the anterior respiratory process, and the posterior respiratory process of the puparia of these two species were analyzed and studied using stereomicroscope and scanning electron microscope techniques. The chaetotaxy of the puparium of each species is also described and illustrated. A taxonomic diagnosis of the larvae of the genus Pelecocera is proposed to separate them from the larvae of other genera of the tribe.

Combined stereomicroscope and SEM disentangle the fine morphology of the undescribed larva and puparium of the hoverfly Milesia crabroniformis (Fabricius, 1775) (Diptera: Syrphidae).

With over 80 species, Milesia Latreille, 1804 is a hoverfly genus (Diptera: Syrphidae) found in all continents except for Australia and the Antarctica. However, little is known about its life cycle and biology. The three Milesia species for which early stages are known have saproxylic larvae, suggesting that the larvae of all other Milesia species are also saproxylic. The early stages of the three Milesia species occurring in Europe are undescribed. Milesia crabroniformis (Fabricius, 1775), a mimic of the hornet Vespa crabro Linnaeus, 1758, is the largest hoverfly in Europe and is listed as Least Concern in the IUCN European Red List of Hoverflies. We here report the first early stages of Milesia ever found in Europe, describing them and their breeding sites. Larvae of M. crabroniformis were collected in water-filled tree holes of live chestnut trees (Castanea sativa Mill.) in Málaga, Southern Spain in 2020-2021. Various studies based on stereomicroscope and scanning electron microscopy (SEM) techniques have proven useful in diagnosing hoverfly early stages by observation of their fine morphology. Thus, these techniques were also used here to characterize the second (L2) and third (L3) stage larvae of M. crabroniformis, as well as the puparium. A Leica M205C binocular stereomicroscope and a Jeol JSM-ITH500HR SEM were used. The head skeleton and chaetotaxy of the L3 larva were described and illustrated. Adjustments to the diagnosis of the larvae of Milesia are proposed based on the number of hooks from the primary row of the main group of hooks. The new early stages are compared with those of other Milesia hoverflies, as well as with those of the sister group Spilomyia Meigen, 1803. The knowledge of the larval biology and breeding sites of saproxylic insects is useful for implementing forest management measures and species' conservation programs.

Effect of UV-Absorbing Nets on the Performance of the Aphid Predator Sphaerophoria Rueppellii (Diptera: Syrphidae).

Photoselective nets have proven to be effective for aphid pest control as they limit their dispersal ability. However, little is known on the impact of such nets on natural enemies of aphids. In this work, we study the effect of UV-absorbing nets on the syrphid fly Sphaerophoria rueppellii Wiedemann (Diptera: Syrphidae), a commercially available aphid biocontrol agent in Mediterranean horticultural crops. First, we released mature syrphid adults and evaluated density and dispersal of the resulting immatures in a turnip crop grown under either UV-blocking (Bionet) or standard net. Second, we assessed, under controlled conditions, the impact of UV radiation on fitness-related parameters, and on flight behavior of S. rueppellii adults. Results showed that, while syprhid immature density was higher, their dispersion was reduced under Bionet. UV-absorbing nets are known to influence the dispersion pattern of aphids, which may have indirectly conditioned the distribution of their predator S. rueppellii. On the other hand, the type of net had no influence on the performance of adults. We conclude that the use of photoselective nets and the release of syrphid predators such S. rueppellii are compatible strategies to be used in IPM aphid-control programs.

Olfactory Response of the Predatory Bug Orius laevigatus (Hemiptera:Anthocoridae) to the Aggregation Pheromone of Its Prey, Frankliniella occidentalis (Thysanoptera: Thripidae).

Herbivore natural enemies base their foraging decision on information cues from different trophic levels but mainly from plant odors. However, the second trophic level (i.e., the herbivorous prey) may also provide reliable infochemical cues for their natural enemies. We have evaluated the role of the aggregation pheromone from Frankliniella occidentalis (Pergande) as a potential kairomone for its natural enemy, the predatory bug Orius laevigatus (Fieber). For this purpose, we have analyzed the response of O. laevigatus to (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate, the two major components of the thrips aggregation pheromone. These compounds have been offered to O. laevigatus adult females and nymphs of the predatory bugs both in separate and as specific (1:1 or 1:2.3) blends, in experiments involving a dual choice Y-tube olfactometer. None of the compounds attracted adults or nymphs when they were individually supplied. Conversely, they were significantly attracted to both adults and nymphs when offered as a blend. A 1:2.3 (R)-lavandulyl acetate:neryl (S)-2-methylbutanoate blend was attractive to both nymphs and adults, while a 1:1 blend elicited response only in nymphs. These results suggest that specific blends of these compounds from the aggregation pheromone may be used as an attractant to O. laevigatus. The results of this work highlight the importance of studying olfactory responses of natural enemies for a better understanding of their foraging behavior. Potential uses of these results in future studies are discussed.

Neotropical Copestylum Macquart (Diptera: Syrphidae) Breeding in Fruits and Flowers, Including 7 New Species.

Ten species of Copestylum (Diptera: Syrphidae) were reared from fruits and flowers in Costa Rica, Ecuador and Trinidad. Seven were new and in this paper, we describe them, their development sites and the third stage larva and/or the puparium of all ten species. One new synonym is proposed, Copestylum pinkusi (Curran) [= Copestylum cinctiventre (Curran)]. Similarities and differences between these new and other Copestylum species, suggest they separate into two groups, referred to as the Vagum and Cinctiventre species groups. Features characterising these groups for both adult and early stages are assessed. Each species was also distinguished using adult and early stage characters. Within the Vagum group, adults were more disparate morphologically than the larval stage; this was reversed in the Cinctiventre group. Adult colour patterns are probably cryptic in function and for disguise. Vagum species have disruptive marks, while the Cinctiventre species have reflective colours. Biologically, the groups are almost distinguished by larval development sites. Vagum species use predominantly fruits and have a larval stage that is relatively generalised in form and habit. Cinctiventre species are confined to developing in flowers and the larva is more specialised. A key to both adult and early stages of all ten species is provided.

A Differential Role of Volatiles from Conspecific and Heterospecific Competitors in the Selection of Oviposition Sites by the Aphidophagous Hoverfly Sphaerophoria rueppellii.

The selection of oviposition sites by syrphids and other aphidophagous insects is influenced by the presence of con- and heterospecific competitors. Chemical cues play a role in this selection process, some of them being volatile semiochemicals. Yet, little is known about the identity and specificity of chemical signals that are involved in the searching behavior of these predators. In this study, we used olfactometer bioassays to explore the olfactory responses of gravid females and larvae of the syrphid Sphaerophoria rueppellii, focussing on volatiles from conspecific immature stages, as well as odors from immature stages of the competing coccinellid Adalia bipunctata. In addition, a multiple-choice oviposition experiment was conducted to study if females respond differently when they can also sense their competitors through visual or tactile cues. Results showed that volatiles from plants and aphids did not affect the behavior of second-instars, whereas adult females strongly preferred odors from aphid colonies without competitors. Odors from conspecific immature stages had a repellent effect on S. rueppellii adult females, whereas their choices were not affected by volatiles coming from immature heterospecific A. bipunctata. The results imply that the syrphid uses odors to avoid sites that are already occupied by conspecifics. They did not avoid the odor of the heterospecific competitor, although in close vicinity they were found to avoid laying eggs on leaves that had traces of the coccinellid. Apparently adult syrphids do not rely greatly on volatile semiochemicals to detect the coccinellid, but rather use other stimuli at close range (e. g., visual or non-volatile compounds) to avoid this competitor.

Antipredator behaviour of Myzus persicae affects transmission efficiency of Broad bean wilt virus 1.

Biological control has the potential to limit the population growth of arthropod vectors and consequently may be expected to reduce plant virus spread in a crop. However, reduction of vector abundance is not the only effect of biological control. Natural enemies might induce antipredator behaviour that affects feeding and dispersal of vectors, and therefore virus spread. Here we test the effect of two natural enemies on dispersal of the aphid vector Myzus persicae and transmission of Broad bean wilt virus 1 (BBWV-1), genus Fabavirus, which is non-persistently transmitted by aphids. One of the predators tested, the syrphid Sphaerophoria rueppellii, is considered to induce low disturbance in aphid colonies, whereas the other, the coccinellid Adalia bipunctata, is assumed to induce high disturbance. Natural enemies enhanced aphid dispersal, but not virus transmission as compared to the control treatment without predators. However, transmission efficiency of BBWV-1 was higher in the presence of coccinellid adults than with syrphids. The behavioural observations of predators and the reactions of aphids to their presence indicate that a stronger antipredator behaviour is induced by coccinellid adults than by syrphids. The different antipredator behaviour displayed by aphids towards coccinellid adults and syrphids might explain the differences found in the rate of virus spread in their presence.

Comparative morphology of early stages of two Mediterranean Sarcophaga Meigen, 1826 (Diptera; Sarcophagidae) and a review of the feeding habits of Palaearctic species.

The third instar larva of Sarcophaga hirticrus Pandellé, 1896 and Sarcophaga javita (Peris, González-Mora and Mingo, 1998) are described and figured for the first. The use of scanning electron microscopy (SEM) has been demonstrated as an effective tool for determining differences at the specific level, and is here applied. The two species are distinguished from other Sarcophaga spp. and the principal diagnostic character states are illustrated and discussed. Comparative information on immature stages morphology of the described Palaearctic Sarcophaga species and its feeding habits are compiled and provided in a tabulated form.