The present paper deals with the lepidopteran fauna that have been recorded during fieldwork at Nordeste County in São Miguel Island. Throughout the 38 weeks’ trials, a total of 10160 adults belonging to 33 lepidopteran species were recorded and listed alphabetically by families, including one species of Argyresthiidae (3%), four of Crambidae (12%), one of Erebidae (3%), five of Geometridae (15%), 18 of Noctuidae (55%), one of Sphingidae (3%), one of Tineidae (3%) and two of Tortricidae (6%) (Table 1). Amongst the most representative families in number of species are Noctuidae, Geometridae and Crambidae, respectively (Table 2). The Noctuidae family has the greatest abundance of individuals (9584; 94.33%) followed by Crambidae (286; 2.81%), Tineidae (129; 1.27%) and Tortricidae (196; 1.04%), while Sphingidae was the least abundant family (4; 0.04%) (Table 2).

The number of trapped adults was consistently higher during spring and summer, decreasing sharply in late autumn (Table 1, Figs 1, 2). Of the 33 species sampled, nine were recorded continuously during all three seasons (spring, summer and autumn), 11 for spring and summer and five species exclusive to spring and eight to summer (Table 1, Fig. 1).

Figure 1.  

Seasonal relative abundance of adult moth species (%) collected in the nursery of Nordeste County, during 2019.

Figure 2.  

Weekly abundance of adult Lepidoptera species captured in the light trap in Nordeste County between March and December 2019. M - March, A - April, M - May, J - June, J - July, A - August, S - September, O - October, N - November, D - December.

In S. Miguel Island, 108 species of moth species are known. Fig. 2 shows that, from 33 moth’s species, 22 were caught in the light trap, mainly Noctuidae, which are amongst the most common constant in the Azorean Archipelago (e.g. Vieira and Karsholt 2010). The mean of individuals (± SE) recorded throughout the 35 weeks of the sampling period are as followed: Autographa gamma (3.26 ± 0.66), Agrotis ipsilon (2.97 ± 0.64), Agrotis segetum (2.77 ± 1.85), Ctenoplusia limbirena (2.69 ± 0.65), Mythimna unipuncta (121.57 ± 17.69), Noctua pronuba (71.49 ± 22.43), Noctua atlantica (0.03 ± 0.03), Thysanoplusia orichalcea (2.89 ± 1.34), Peridroma saucia (18.97 ± 7.90), Phlogophora furnasi (0.26 ± 0.12), Phlogophora interrupta (1.23 ± 0.33), Phlogophora meticulosa (1.51 ± 0.37), Xestia c-nigrum (36.71 ± 8.65), Galgula partita (6.97 ± 1.92), Mesapamea storai (0.03 ± 0.03), Sesamia nonagrioides (0.14 ± 0.08), Helicoverpa armigera (0.31 ± 0.19) (Noctuidae), Agrius convolvuli (0.11 ± 0.09) (Sphingidae), Palpita vitrealis (2.12 ± 0.49), Udea ferrugalis (5.69 ± 1.46) (Crambidae), Hypena obsitalis (0.54 ± 0.22) (Erebidae) and Opogona omoscopa (3.63 ± 1.20) (Tineidae).

The most abundant noctuid species were M. unipuncta (41.88%), N. pronuba (24.63%), X. c-nigrum (12.65%), P. saucia (6.54%) and G. partita (2.40%), as had been observed in previous studies (Silva et al. 1994, Silva et al. 1995, Silva et al. 1995a, Silva et al. 1995b, Vieira et al. 2004), while the least abundant included, for example, the endemic species M. storai, N. atlantica and N. carvalhoi, accounting for only 0.01% of the total adults sampled (Table 1; Fig. 2).

Weekly abundance of the most frequent nocturnal lepidopterans were similar to those observed in previous studies conducted in the Azores (e.g. Tavares 1989, Carvalho et al. 1999, Vieira et al. 2004). In particular, for M. unipuncta, it was observed that, after three remarkable peaks of captures in early July, August and September, there was a steady decline to the lowest values in mid-October, in addition to the low number of adults captured (nil in some weeks) in early winter and spring. The number of adults captured varies significantly depending on the type of trap (light trap or sex pheromone trap), location and season (Vieira et al. 2004). The collected moths were from the adult stage, but larvae of the most abundant species do not feed on woody plants.

Concerning sex ratio, for 13 moth species caught in the light trap, it was biased towards females, namely: A. gamma (65%), A. ipsilon (67%), A. segetum (63%), C. limbirena (67%), M. unipuncta (60%), N. pronuba (62%), T. orichalcea (62%), P. saucia (65%), P. interrupta (70%), P. meticulosa (57%), H. armigera (55%), S. nonagrioides (60%) and A. convolvuli (75%). The biased ratio of females to males in these species may occur periodically and is probably related to their non-seasonal migratory movements (see also Silva et al. 1994, Silva et al. 1995a, Silva et al. 1995b, Vieira et al. 2004).

Regarding E. postvittana, 104 males were captured in the sex pheromone trap (Table 1; Fig. 3), corresponding to the mean (±SE) weekly number of 3.33 ± 0.65 individuals. According to Oliveira et al. (2022), this number was lower than that observed at Furnas (N = 300; 9.68 ± 1.98) over the same sampling period, although the annual pattern of adult distribution was relatively similar for both sampling sites. The continuous presence of the moth larvae year-round, complemented with the information resulting from the captures of adults in sex pheromone traps, allowed us to identify the light brown apple moth, E. postvittana, as a major lepidopteran pest that attacks endemic and native plants of the Azorean Forest (Oliveira et al. 2022).

Figure 3.  

Males of Epiphyas postvittana caught weekly in the sex pheromone trap installed in Nordeste Nursery between May and December 2019.

Sampling of Microlepidoptera moths on young forest plants reared in the Nordeste Nursery using an entomological net showed that the most common moths are endemic species that appear associated with their known host plants (Table 3) (see Silva et al. 1995, Nuss et al. 1997, Wagner 2014, Wagner 2015, Borges et al. 2018, Pérez Santa-Rita et al. 2018). Argyresthia atlanticella is the second most common lepidopteran in the Azores (Peres Santa-Rita et al. 2020), but in the nurseries, they have population densities with low numbers of individuals (Table 1), which is, amongst other factors, related to their nocturnal (rather than diurnal) activity and some of these species are effectively rare or have a conservation status of vulnerable.

Table 3 shows that 33 lepidopterans recorded are classified with the colonisation status of endemic (10 species), native (16), introduced (4) and introduced/naturalised (3). Regarding their feeding mode, 23 are generalists or polyphagous and 10 are specialists and the larvae can feed on plants of the Laurel Forest (14 species), endemic / native (23 species) and non-native (23 species).

According to previous studies and our field observations, many of the moth species recorded in this study (see Tables 1, 3) have little economic impact in the Azores Archipelago, but others may constitute a potential risk as pests (e.g. species from families of Noctuidae, Tortricidae and Crambidae) of introduced/naturalised and/or endemic/natives plants. For example, in contrast to the low number of Palpita vitrealis adults caught in the light trap (Table 1, Fig. 2), its larvae were observed to strongly and exclusively attack Picconia azorica plants grown at the Nordeste Nursery and could reach 16.3% of the plants sampled (cf. Oliveira et al. 2022). On the other hand, Cyclophora azorensis larvae attacks their host plant Erica azorica, while Argyresthia atlanticella larvae feed on Erica azorica, Vaccinium cylindraceum and Morella faya male flowers and green fruits and occur both in Laurel Forest habitats and in different types of habitats disturbed with Morella, Erica or Vaccinium. Additionally, A. fortunata azorica preferentially feeds on Morella faya (e.g. Silva et al. 1995, Nuss et al. 1997, Wagner 2014, Wagner 2015, Borges et al. 2018, Pérez Santa-Rita et al. 2020). Other studies (Ribeiro et al. 2005, Rego et al. 2019) show that these species are associated with different hosts (e.g. A. fortunata on E. azorica), but neither shows that their impact severely affects plant fitness/reproduction. In addition, herbivore abundance may match host plant abundance, not being necessarily a pest.

Our results provide information on the diversity of moths (Insecta, Lepidoptera) present in Nordeste County, whose adults were sampled in the Nordeste Forest Nursery. A total of 10160 adults belonging to 33 lepidopteran species were recorded and listed by families, including: Argyresthiidae, Crambidae, Erebidae, Geometridae, Noctuidae, Sphingidae, Tineidae and Tortricidae.

In general, the temporal profile of the abundance of adults caught in a light trap and a sex pheromone trap reveals that the Noctuidae, followed by the families Geometridae and Crambidae, have the highest species diversity and that these have high population densities during spring and summer, decreasing sharply in late autumn. In addition, for 13 species caught in the light trap, the adult sex ratio was favourable to females.

From the literature and our field observations, we conclude that many of the moth’s species recorded have little economic importance in the Azores Archipelago, but others may constitute a potential risk as pests (e.g. species from families of Noctuidae, Tortricidae and Crambidae) of introduced/naturalised and/or endemic/natives plants. In fact, the high abundance of adult moths observed for some species whose larvae feed preferentially on native and/or exotic herbaceous plants does not generally represent very serious damage to endemic and native forest plants of the Azores.

Some biological control agents are present in the field, for example, parasitising the larvae of E. postvittana (i.e. Braconidae species of Meteorus ictericus (Nees, 1811) and Microgaster opheltes Nixon, 1968) and of M. unipuncta (i.e. Glyptapanteles militaris Walsh, 1861), as well as preying on several Noctuidae larvae (e.g. Calosoma olivieri Dejean, 1831, Coleoptera, Carabidae).

An analysis of the colonisation status of the lepidopteran moth species and their feeding and primary host plants associated with the Laurel Forest, native or non-native Azorean plants, suggests that forest nurseries may help us to understand the establishment of lepidopteran moths (endemic, native or exotic species) in Laurel Forest environments.

Finally, more studies are needed to understand two fundamental objectives; first, to know the potential damage caused by moth species on endemic and native Azorean plants; second, to assess the conservation status of all these moth species and to advise on possible future research and conservation actions critical to the long-term survival of the most endangered species.