When I went to Puerto Rico in January, I was taken aback by the many butterflies I saw, especially in the drier area of the southwest (and many more than I could recall from my childhood days), so I decided to find out a little more. [Did not find much, so I will definitely consult my co-blogger about this!] I did find articles from late May and early June that commented on the larger-than-usual number of butterflies.
El Nuevo Día (31 May 2016) wrote that the end of the dry season in Puerto Rico and heavier rains in May facilitated reproduction of butterflies on the island, an event that was observed by many and shared through different social media networks, for example, Facebook pages such as Mariposas en Puerto Rico, Guardianes de las Mariposas de Puerto Rico, and Mariposas de Puerto Rico.
One example they gave was the central western mountain town of Maricao, where thousands of butterflies were seen flying through the area. The article stressed that unlike the previous two years, when there was a serious drought in Puerto Rico, this year saw more rain, which helped plants to bloom and grow new leaf buds, which provide nourishment for adult butterflies and caterpillars.
The article also stressed that there are around 90 (native or endemic) species of butterflies in Puerto Rico. The most famous endemic species on the island is the harlequin butterfly (found in Quebradillas and other areas with karst formations), which is endangered due to loss of habitat and pollution.
Meanwhile, Metro (1 June 2016) reported on sightings of a massive migration of butterflies on the coast of the western town of Aguadilla, also documented in pictures and videos. Entomologist Luis Hernández explained that when it starts to rain, “plants in the southern area begins to get green [. . .] and to sprout new, tender leaves that caterpillars need to eat. What happens is that the cocoons are waiting for rain; after extended precipitation, caterpillars begin to feed on new green leaves that are growing due to the rainfall.” Meteorologist Deborah Martorell added that there is no reason to worry, as this population explosion of butterflies encourages pollination, which in turn helps to agricultural areas and also strengthens the food chain for other species such as lizards and birds.
The article also underlined that the wind blowing from the east and southeast is responsible for the heavy butterfly populations in western and northwestern towns such as Aguadilla, Mayaguez, and mountain towns such as Maricao, among others, because butterfly migrations “are aided by the winds” as the butterflies seek flowering plants to feed the adults,” as Hernández explained.
[[Photo above by Tony Zayas: Monarch butterflies in Puerto Rico; photo of a Harlequin butterfly (Atlantea tulita) from Mi Puerto Rico Verde: http://www.miprv.com/mariposa-arlequin-especie-endemica-en-peligro/]
For original articles (in Spanish), see http://www.elnuevodia.com/ciencia/ciencia/nota/abundanteslasmariposasenpuertorico-2205219/ and http://www.metro.pr/noticias/entomologo-explica-migracion-masiva-de-mariposas-en-playa-de-aguadilla/pGXpfa!QNVosVmJ4glo/
Also see the 2009 book Mariposas de Puerto Rico [Butterflies of Puerto Rico] at https://www.amazon.com/Butterflies-Puerto-Rico-Las-Mariposas/dp/0982238800