The investigation followed collections of diamondback moth larvae made in Guanajuato from 2020 through 2024. These collections had repeatedly yielded an unidentified braconid that was more common than the ichneumonid parasitoid Diadegma insulare at some localities, raising the possibility that the species could have an important role in suppressing the moth. The diamondback moth is a Mediterranean-origin pest distributed around the world and responsible for substantial damage to brassica crops. More than 135 species of its parasitoids have been identified, with Diadegma, Apanteles and Microplitis regarded in some regions as particularly important genera. The research therefore addressed a practical question about natural enemies while also resolving the taxonomic identity of the newly encountered wasp.

For conventional identification, the researchers examined specimens from seven Guanajuato localities and compared them with the detailed original description of A. piceotrichosus, a 2014 revision of 205 Mesoamerican species of Apanteles, and historical records of Apanteles associated with diamondback moth. The Mexican material corresponded closely to published illustrations, measurements and descriptions of body colour, sculpture, antennae, thorax, wings, metasoma and ovipositor sheaths. Particularly useful diagnostic traits included a 15th antennal flagellomere 1.2 to 1.4 times as long as wide, a mostly pale pterostigma with thin brown margins, dark fore and middle femora, a propodeum with a weak areola confined mainly to its posterior half, and ovipositor sheaths slightly shorter to approximately equal in length to the metatibia. The first metasomal tergite narrowed strongly toward its posterior margin, and the second was trapezoidal to subtriangular and nearly smooth apart from a few weak punctures.

These characters separated the Mexican specimens from three other Apanteles species previously recorded as diamondback moth parasitoids in the New World. Apanteles alexanderi has a nearly cubic final antennal segment, a mostly parallel-sided first tergite, a second tergite bearing more evident punctures, yellow fore and middle femora, and ovipositor sheaths substantially longer than the metatibia. A. epinotiae likewise has a cubic to subcubic final antennal segment, a first tergite that is mostly parallel-sided, and a stronger, complete propodeal areola, together with different wing and vein coloration. A. sodalis has a pterostigma that is almost entirely brown apart from a pale basal spot, stronger striae on the second tergite, a subrectangular and parallel-sided second tergite, and a brown tegula. The contrasting combination observed in the Guanajuato material supported identification as A. piceotrichosus. The species had not been included in the Mesoamerican revision because it was then considered restricted to South America.

Molecular data provided a separate line of support. The investigators extracted DNA from 10 Apanteles specimens and amplified the mitochondrial 16S and COI genes and the nuclear 28S ribosomal RNA marker. The resulting amplicons were 451, 383 and 487 base pairs for 16S, COI and 28S, respectively, and each product was sequenced from both strands. A representative COI sequence, assigned to specimen CEAM-Hy-023 and deposited in BOLD, allowed the species to be recognized through DNA barcoding. It differed by 38 to 40 base pairs, or 5.91 to 6.09 percent, from the closest BOLD entries, Apanteles javiercontrerasi and Apanteles carlosguadamuzi. The analysis therefore confirmed that the parasitoid belonged to Apanteles and was consistent with the morphological determination as A. piceotrichosus.

Maximum-likelihood analyses added information about the wasp’s genetic placement, although the principal molecular aim was to determine whether the barcodes alone could characterize the species. The COI analysis included 95 sequences and 322 aligned nucleotide positions, with Agathirsia davidi used as the out-group. Under the Tamura–Nei model, the highest-log-probability tree had a value of −7297.69. A second analysis combined the 16S, 28S and COI sequences into an 865-position dataset containing eight sequences, with Alphomelon sequences serving as the out-group; the highest-log-probability tree in that analysis had a value of −1951.31. The inferred relationships placed the Mexican material near Glyptapanteles merope and Apanteles melpomene, both recorded from Malaysia. These tree-based relationships were treated as additional phylogenetic context rather than evidence that the Mexican population had originated from either Malaysian species.

Laboratory observations showed that A. piceotrichosus behaves as a solitary koinobiont endoparasitoid of diamondback moth larvae. Successful parasitism was recovered from second- and third-instar hosts, while no parasitoids were recovered from fourth-instar larvae. The egg was described as translucent, elongated and hymenopteriform, with a short pedicel. The first-instar parasitoid larva possessed a pair of jaws and an apparent anterior head region wider than the remainder of its body. From the second instar onward, an anal vesicle was visible and enlarged as development proceeded. The investigators considered five larval instars probable, but they did not determine the duration of each individual instar. The study also noted that observations involving first-instar hosts were insufficient to establish whether apparent parasitism in early hosts was successful, leaving the preferred host instar for further testing.

Under laboratory conditions of 25 ± 2 degrees Celsius, 70 percent relative humidity and a 12-hour light-to-dark photoperiod, the mean egg incubation period was 0.92 ± 0.00 days. The larval stage lasted 5.86 ± 0.01 days, and the pupal stage lasted 5.65 ± 0.02 days, giving a mean development time from egg to adult of 12.43 ± 0.01 days. As the parasitized host neared pupation, the parasitoid larva pierced the moth larva’s integument, emerged, consumed its host fluids and then spun its own cocoon. The pupa was exarate and yellowish, whereas newly emerged adults were completely black. These developmental timings were similar to an egg-to-adult period of 12.63 days previously reported for A. machaeralis and a range of 11 to 14 days reported for A. syleptae.

Adult longevity varied sharply according to the food provided. Males and females supplied with a honey solution lived an average of 17.58 ± 0.54 and 16.08 ± 0.19 days, respectively, whereas males and females given only water survived for 2.42 ± 0.51 and 3.08 ± 0.08 days, respectively. These observations establish the basic developmental and survival characteristics of the newly recorded Mexican population, but they do not measure the wasp’s ability to reduce diamondback moth damage in crops. Earlier work in another location reported parasitism of approximately 17 percent, while the broader biological information on A. piceotrichosus remained limited. The authors consequently emphasized that further work is required to determine the species’ role as a field-based natural enemy. The first Mexican and North American record expands the known geographic range of the wasp and provides a baseline for investigating its possible contribution to natural control of a major agricultural pest.

Subject of Research: First North American record and laboratory biology of the diamondback moth parasitoid Apanteles piceotrichosus.

Article Title:  Apanteles piceotrichosus Blanchard ( Hymenoptera , Braconidae ), first record from México, new molecular and biological data

Article References: Rodríguez-Rodríguez, S. E., Fernández-Triana, J. L., Lomeli-Flores, J. R., Martínez-Núñez, M., Rodríguez-Leyva, E., González-Hernández, H., & Bernal, J. S. (2025). Apanteles piceotrichosus Blanchard (Hymenoptera, Braconidae), first record from México, new molecular and biological data. Journal of Hymenoptera Research, 98, 339-353. https://doi.org/10.3897/jhr.98.138425

Image Credits: AI Generated

DOI: 10.3897/jhr.98.138425

Keywords: Apanteles piceotrichosus, diamondback moth, parasitoid wasp, Guanajuato, Mexico, DNA barcoding, molecular phylogeny, insect taxonomy, crop pest, natural pest control, Apanteles, piceotrichosus

The macadamia is not an ordinary crop. Labour-intensive harvesting and complex post-harvest processing make it one of the costliest nuts in the global market, which means that every percentage point of yield lost to insects translates into substantial economic damage. Protecting the trees from pests is therefore a central concern for growers, and the conventional response has often been intensive chemical or mechanical intervention. The new research suggests that an alternative, ecologically grounded strategy may already be flying overhead every night. By examining how natural vegetation in and around plantations shapes the communities of birds and bats that forage among the trees, the team set out to quantify the pest control services these animals provide and to identify the landscape features that sustain them.

The study was conducted at ten intensively managed macadamia plantations in South Africa, a design that allowed the researchers to capture variation in both management intensity and surrounding land cover. At each site, the team compared trees growing at the edge of the plantation with trees in the centre, a comparison specifically chosen to analyse the influence of the surrounding vegetation on the animals visiting the crop. Edge trees sit closer to hedgerows, forest fragments and other natural features, while central trees are embedded more deeply within the monoculture, so any systematic differences in pest damage or animal communities between the two positions can reveal how strongly the wider landscape shapes what happens inside the orchard.

Surveying the fauna required two very different techniques. The researchers recorded 111 bird species through direct observation, walking the orchards and documenting the birds foraging among the trees. Bats, being nocturnal and difficult to observe visually, were detected through their echolocation calls, which were captured with acoustic recording equipment and used to identify 16 species. This acoustic monitoring allowed the team to build a detailed picture of which bat species were active over the plantations, how their activity varied between sites, and how that variation related to the structure of the surrounding landscape and the level of insect damage measured on the nuts.

The results pointed clearly to bats as the dominant pest control agents in the system. Bat activity was associated with reduced insect damage, and this effect was particularly pronounced in plantations that contained less natural habitat within their boundaries or were surrounded by natural habitat in the wider landscape. Natural habitat, in the sense used by the researchers, includes native forests, bushland and scrubland, the heterogeneous vegetation types that provide roosting sites, foraging grounds and refuge for insectivorous bats. In landscapes where these features persisted, the bats appeared to compensate for the scarcity of on-farm natural cover, patrolling the orchards and suppressing the insect populations that would otherwise feed on the developing nuts.

To test the contribution of flying vertebrates directly, the team conducted exclusion trials, a classic experimental approach in which nets are used to keep birds and bats away from the trees. The outcome was striking. When birds and bats were excluded, the proportion of nuts damaged by insects rose from 6.2 per cent to 10.7 per cent, an increase of roughly 70 per cent. This experiment provides some of the most direct evidence that these animals deliver a measurable, economically meaningful service to macadamia growers. Intriguingly, however, the researchers could not demonstrate a direct influence of bird numbers on pest infestation, suggesting that in this system the nocturnal bats, rather than the diurnal birds, carry the primary burden of biological pest control.

The landscape context proved to matter in more ways than one. As the proportion of natural habitats around the plantations increased, not only did the number of bats rise, but their diversity increased as well, indicating that intact vegetation supports a richer community of these aerial predators rather than merely a larger one dominated by a few generalist species. Even the yield of the macadamia trees was linked to the share of natural habitat in the landscape, reaching its highest level when natural habitats accounted for around 60 per cent of the surrounding area. This peak suggests a non-linear relationship in which a substantial but not exclusive share of natural cover best supports the ecological processes, from pest suppression to pollination, that underpin crop production.

Bird communities, by contrast, responded to fine-scale structure within the plantations rather than to the broader landscape. The researchers found that the species assemblages differed between the edges and the centres of the orchards: species that prefer dense and woody vegetation were more common at the plantation edges, while species of open habitats predominated in the interior. This edge-to-centre gradient shows that even within a single intensively managed plantation, the arrangement of vegetation creates distinct niches for different bird species, and it hints that the conservation value of an orchard depends not only on what surrounds it but also on how its own internal habitat mosaic is structured.

The implications extend well beyond macadamia. Lead author Dr Mina Anders of the Department of Functional Agrobiodiversity and Agroecology at the University of Göttingen emphasised the broader message of the findings. Natural habitats, she explained, are valuable refuges that support beneficial organisms providing pollination and pest control, which in turn benefits agricultural production and the farmers who depend on it. It is therefore essential, she argued, that natural habitats and their conservation are incorporated into the planning of agricultural land. In other words, the patches of native forest, bushland and scrubland that persist between and around fields should not be viewed as idle or expendable land, but as functional infrastructure that actively contributes to farm productivity.

For a crop as valuable as the macadamia, the economics of this ecological service are compelling. A 70 per cent increase in insect-damaged nuts when bats and birds are excluded illustrates how quickly quality, and with it market value, deteriorates without these natural allies. The study thus highlights a form of agriculture that combines biodiversity with production, in which conserving natural vegetation within and around farmland is not a concession to environmental ideals but a practical investment in yield and nut quality. As global demand for macadamias continues to grow, the research offers growers and land-use planners a concrete, evidence-based reason to protect the forests and scrublands that shelter the bats working the night shift over South Africa’s orchards, and it adds macadamia plantations to the growing list of cropping systems where the fate of the harvest is quietly tied to the health of the surrounding landscape.

Subject of Research: The role of bats, birds and natural habitat in biological pest control in macadamia orchards

Article Title: Bats as a form of biological pest control

Article References: Bats as a form of biological pest control. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: bats, biological pest control, macadamia, South Africa, agroecology, natural habitat, biodiversity, bird communities, echolocation, crop yield, landscape management, University of Göttingen