Originally Photinus palaciosi was described as Macrolampis palaciosi by Zaragoza-Caballero (2012). In 2020, this species was moved into the genus Photinus (Zaragoza-Caballero et al. 2020).

Photinus palaciosi is an emblematic firefly species endemic to the TransMexican Neovolcanic Belt and Sierra Madre Oriental of Central Mexico. This species is widely recognized among Mexican fireflies due to its synchronous courtship behaviour during the breeding season. During this period, thousands of fireflies gather in the wooded areas of this region to engage in courtship and mating. These unique characteristics have transformed this species into a significant tourist attraction that stands out annually. Females of Photinus palaciosi are brachypterous, and therefore dispersal ability is limited. While the geographical distribution is fairly well understood, there is still a lack of data to estimate the population size. The threats facing the species are known, at least in most of the sites where the species is documented. These threats include habitat loss, mass tourism, the use of agrochemicals, and light pollution. While the extent of occurrence is outside the threshold for listing in a threatened category, the area of occupancy (AOO) is limited. It is estimated at 84 km2, based on existing records. While this number could climb slightly as new occurrences are discovered, given the limited suitable habitat, it is unlikely it would increase more than 10 fold. Declines in local abundance and area of occupancy (AOO) have been observed in some places, according to anecdotal reports from residents within the range of the species. Habitat quality decline has also been observed. Nine or ten locations are considered for this species. The constant threat of habitat loss is present in all the sites where this species has been recorded (29), with some of these sites exhibiting a higher degree of fragmentation compared to the surrounding habitat. Tourism poses a significant threat, as it can lead to habitat degradation, light pollution, and a reduction in reproductive success. This activity represents a major threat at 24 of the registered sites, spanning across 5–6 locations (many of these sites are close to each other, allowing for simultaneous impacts). Agricultural intensification and the resulting use of pesticides are identified as the primary threat in three locations. Since these locations are distant from each other, they are considered as three independent locations. Additionally, two localities are within one location in Mexico City, where they face risks due to the increasing levels of light pollution associated with urbanization. Therefore, under the criteria B2ab(ii,iii,v), this species is classified as Vulnerable.

Photinus palaciosi is endemic to mountainous areas of Central Mexico, in the area that corresponds to the Eje Neovolcánico Transversal or Trans-Mexican Volcanic Belt and a part of Sierra Madre Oriental (municipality of Tlanchinol). It has been recorded from 29 localities within five different states: Tlaxcala, Estado de México, Mexico City (CDMX), Hidalgo and Puebla (Naturalista 2023, GBIF.org 2023, CONABIO 2024, Gutiérrez-Carranza et al. 2023, T. López-Palafox pers. obs.).

This species is distributed at an altitudinal range from 1,520 to 3,300 meters above sea level. Due to the environmental characteristics of its habitat, it is possible that P. palaciosi could also be distributed in the areas surrounding the localities where they have been reported to date. It is necessary to carry out more surveys in those areas to better understand the current distribution of the species, because new localities for the species have been discovered recently.

The species has disappeared in recent years from some historic localities. According to anecdotal reports, this species used to occur in the town of Nanacamilpa in high densities. However, to date it is almost impossible to find them inside the current urbanized zone where they used to live.

Its estimated extent of occurrence (EOO) is approximately 180,969 km², and its area of occupancy (AOO) is 84 km², though this has likely declined since records began because, as noted, the firefly has disappeared from some areas. However, it is possible EOO and AOO are slightly larger than reported, as new occurrences are still being found. Based on currently know occurrences, the species is distributed in nine or ten locations.

Currently, there is no information about population size for this species. The authors have visited most of the places where this species occurs and observed that the populations are more abundant in Nanacamilpa in comparison with another site, Amecameca de Juárez.

Population declines have been noted in some areas. The inhabitants of Nanacamilpa mention that in 2021, the number of fireflies that emerged as adults was much lower compared to previous years, even when there was no access to tourists due to the pandemic in the year prior. It is now only possible to find the fireflies within the forest and no longer in the most populated areas. The absence of fireflies in the city is notorious, as well as the contrast of their presence in areas with greater tree coverage, such as within the forest. Therefore, a population decline is inferred. In addition, the hatch timing of adults was delayed; in 2021 it was possible to see them starting the last week of June, and in past years, it was possible to observe them starting at the end of May or the beginning of June.

The abundance of firefly populations is currently being studied at two sites in the state of Tlaxcala (Nanancamilpa and Calpulalpan), however there is still no data in this regard.

Photinus palaciosi can be found in oyamel-pine forests (INAFED 2010a), oak-pine forest (INAFED 2010b, Rojas et al. 2016, SEMARNAT 2012) and pine forest remnants. All occurrences are found in forests near volcanoes. These forests are distinguished by being humid, especially in the months of May to August, which seems to be a fundamental requirement for fireflies in this species.

This is a species with a synchronous bioluminescence flash pattern. Females are brachypterous, therefore they are unable to fly and have a low dispersal capacity. There is no record of how far they can move. The operative sex ratio is strongly skewed towards males. We have observed intense sexual competition between males for access to females, counting up to 8 individuals trying to copulate with a female (López-Palafox pers. obs.). The females move vertically, emerging from the ground and going up to the vegetation, this occurs during the reproductive period. Females flash differently than males.

They have annual life cycles. According to observations by R. Campos (pers. comm. 2017), females lay their eggs from the end of July to the beginning of August; most larvae hatch between late August and early September. Their larval stage lasts approximately five months (from September to January), later they pupate and remain in this stage for three months (from February to May). By the end of May, the fireflies begin to emerge as adults. The reproductive period lasts for approximately two and a half months (end of May until the second week of August).

The adult fireflies of this species primarily inhabit underground environments, with surface activity limited to their courtship rituals. Similarly, their larval stage is predominantly subterranean, and some individuals are known to be associated with accumulated litter in ravines. This species exhibits a habitat specialization, as it is primarily found in pine forests within the central region of Mexico. As for their diets, larvae of these fireflies have been observed preying on earthworms (R. Campos pers. comm. 2017).

Reproduction in this species spans approximately two and a half months, commencing from the last days of May and extending through June and July, concluding by the second week of August. These fireflies engage in breeding congregations, with hundreds or even thousands of individuals coming together in synchronized gatherings to carry out their reproductive activities. This synchronous behaviour characterizes their mating rituals.

The courtship activity of this species occurs at night, with fireflies initiating their courtship rituals around 8:30 pm and typically concluding by approximately 9:30 or 10:00 pm in the majority of cases. Their courtship signal system is characterized by synchrony, where multiple individuals coordinate their flashes or light emissions. The females of this species are brachypterous, meaning they have reduced or non-functional wings. There is no observed behaviour of egg guarding in this species.

The females of this species are polyandrous, this means that they are able to copulate with more than one male. However, copulas are prolonged, so per night they only have one mate (Vergara et al. 2023)

An aspect of utmost relevance has been pointed out by researchers S. García de Jesús and J. Suárez (pers. comm. 2023) from the Autonomous University of Tlaxcala; according to their findings, a significant correlation has been identified between specific locations in the state of Tlaxcala where the presence of P. palaciosi has been reported and mountain drainages. Also, S. Ramírez-Manzano (2023) reports that temperature, dew point, humidity, and heat index affects the abundance of Photinus palaciosi. These findings underscore the crucial importance of humidity in the environment for the survival and presence of the species. It is a species with restricted distribution and is endemic to Mexico.

Habitat loss is likely the most serious threat impacting Photinus palaciosi. This species used to occur in the town of Nanacamilpa, however now it is impossible to find the species inside the urban settlement (where they used to live). The inhabitants of Nanacamilpa who coexist with this species agree the localized abundance of P. palaciosi has decreased dramatically in less than 40 years. The tenants (aged from 60 to 40) mention that before it was possible to find many fireflies, even among houses within urban settlements; in fact, they mention observing fireflies mating outside the houses. Now it is only possible to observe P. palaciosi in the forest on the outskirts of the town. Some residents report that fireflies began to disappear from the town when street lighting was introduced.

Tourism affects firefly occurrences through the continued degradation of habitats where adult courtship takes place, as well as habitats used for egg laying, larval prey capture, growth and development, and pupation. The continuous opening of trails and the compaction of the soil due to the transit of tourists is a very important factor, since this species spends most of its life on the ground; in fact, the only time this species "leaves" the ground is during the courtship and mating period, in which the males fly and the females climb the grasses.

Artificial light at night (ALAN) also represents a latent risk for this species. As this species requires dark conditions in order to communicate with their conspecifics, light pollution could affect the ability of males to locate female mates (Lewis et al. 2020). Despite the fact that the sanctuary is “isolated” from human settlements, light radiated from these settlements reaches the sanctuary, especially in the parts of the forest where the tree cover is not as abundant. This threat is the most concerning for the region of Mexico City (CDMX), since Bosque de Tlalpan, where the fireflies are found, is a forest remnant surrounded by the city.

There are also agricultural crops, including corn, alfalfa, and other vegetables for subsistence as well as commercial use, within and around the forest habitats of this species. Interviews carried out with local residents revealed until about five or six years ago, the land was rented to potato planters who used Furadan, a highly toxic pesticide both for the environment and for people. The residents mentioned that at present, it is no longer profitable to rent the land to the potato planters, because at the end of the harvest the soil is completely sterile and parched. However, in 2021 potato cultivation was still observed on land within the sanctuary (T. López-Palafox pers. obs. 2021). The consequences of the use of Furadan are immediately devastating; it causes soil pollution and kills many forms of life, and also leaves the soil practically sterile or withered. It has a direct and a strong impact on fireflies, since most of the life cycle takes place within the soil. In addition, research suggests this agrochemical leaks into the soil and can take dozens of years until it is completely washed out, thus contaminating the surrounding land by which it is filtered. This likely indirectly impacts P. palaciosi, as most of its activities of fireflies and their prey occur on and within the soil.

Regarding commercial forest exploitation, which represents 63% of the area covered by forests in which P. palaciosi lives, a third is located in the municipality of Nanacamilpa. Most of the fragmentation in the forests of Tlaxcala is due to logging, which is one of the three main economic activities in the area. Despite the fact that the National Forestry Commission (CONAFOR) established logging quotas in order to maintain the forest, illegal logging activity is carried out throughout this area. This threat is also an important one in the area of Estado de México and Puebla.

The information provided in this section is part of a case study for Mexican fireflies by Paola Velasco Santos (unpublished).

One of the activities that has gained great interest in recent years, is tourism around the reproductive season of Photinus palaciosi. Since 2012 the number of tourists has increased exponentially. In 2012, some residents set out to safeguard the forest and promote tourism, conservation, and firefly research by certifying certain patches of forest as Voluntary Natural Protected Areas (ADVC, SEMARNAT and CONANP 2020). One such area, totalling 940 hectares, was named Santuario de las Luciérnagas (Sanctuary of Fireflies). Firefly tourism in Mexico has grown dramatically in recent years. In 2013, approximately 51,000 tourists came to Nanacamilpa to observe fireflies during their mating season from mid-June to mid-August, and in 2015 the number increased to 71, 636. In the 2016 season there was a flow of 90,000 tourists reflecting an increase of 25.6% compared to 2015 (Castro 2016 in García Trujillo et al. 2018). By 2019, the number of tourists had increased by more than 200% (about 120,000 visitors) arriving at about 24 sites (Avendaño 2020). The success of this activity in Nanacamilpa has encouraged many other towns and communities to promote tourism focused on P. palaciosi sightings, with the hope of increasing their economic prosperity. As a consequence, the number of firefly tourist sites has grown rapidly, and by 2020 there were 31 sites in Tlaxcala (including Nanacamilpa and Calpulalpan), 14 in Puebla, and four in the State of Mexico.

Followed by Tlaxcala, the most popular firefly sites are in the state of Puebla. According to ethnographic research conducted in 2019 (Velasco, in progress), more than 60,000 tourists came to see fireflies at the 14 sites there. In the State of Mexico, local Amecameca authorities estimated that in 2018, around 20,000 tourists visited the three main sites (Lázaro 2018). In other states, firefly tourism is such a new phenomenon that information on its range and focal species remains scarce.

No limits have been set on the number of tourists, and increased visitation rates (mass tourism) and insufficient enforcement of the rules have raised concerns about negative impacts on firefly reproduction and survival. The possible negative effects that these activities have on firefly habitat are obvious.

In the past, some fireflies were harvested for luciferin, which is used in food safety and biomedical research (Lewis 2016). However, there is no evidence this is the case for Photinus palaciosi.

This species is not known to occur in any protected areas and it is not protected by any national, regional, or international legal measures. Though local residents and the providers of tourist services are increasingly aware of the importance of the conservation of this species, at present, there are no actions aimed at the protection of Photinus palaciosi. Management actions are urgently needed. Some actions aimed at mitigating the possible negative impacts of tourism include, clearly defining the paths for the transit of tourists and ensuring paths are followed, avoiding mass tourism by regulating the entry of visitors, and minimizing the artificial light sources used within the Sanctuary. If any source of lighting is required, the recommendations of the International Dark Sky Association (https://darksky.org/) should be followed (Owens et al. 2020, Sanders et al. 2021).

It is necessary to carry out additional samplings in the localities surrounding the areas in which the presence of this species has been reported.