LYCAENIDAE  -  Strymon

Larval diagnosis (Detailed)

Several ports, mostly in the eastern United States, have intercepted lycaenid larvae on pineapple from Latin America over the last several decades (Weisman 1986, Kane 2008). These larvae have a short front that does not reach the epicranial notch, five teeth and two setae on the mandible, a very short second and third segment of the labial palpus, a small triangular prothoracic shield covered with setae, a small honey (= Newcomer's) gland on the posterior portion of A7, and the spiracle of A8 moved dorsad of the other abdominal spiracles. The body setae are pointed and unmodified except for those surrounding the gland. We did not find a detailed larval description of any New World pest species of Lycaenidae on pineapples; however, several lines of evidence support an identification of Strymon.

First, literature records associate Strymon with pineapple (see review in Robbins 2010). With regard to Costa Rica and Central America, where most recent port interceptions originated, Strymon is known as the pineapple borer (Saunders et al. 1983) or just fruit borer (Vargas Carrillo 2011). It is specifically mentioned as a pest of pineapple in Mexico (McGuire and Crandall 1967), Guatemala (Carter 1934), and Costa Rica (Coto and Saunders 2004). The study by Harris (1927) in Trinidad probably refers to this species as well.

At the species level, Robbins (2010) listed four taxa associated with pineapple: Strymon ziba, S. megarus, S. lucena, and S. oreala. The first two names are considered "superspecies" complexes that potentially could be divided in the future. He noted most published records lump S. ziba and S. megarus and misidentify them under the names Thecla basilides, Thecla basalides, or Tmolus echion. As defined by Robbins and Aiello (1982), T. echion feeds only on dicots. A recent host list of Neotropical butterflies (Beccaloni et al. 2008) listed four species of Lycaenidae on pineapple (Strymon legota, S. megarus, S. oreala, and a riodinid - Napaea eucharila) plus other doubtful or incomplete records (Pseudolycaena marsyas, either S. megarus or S. ziba in publications from Mexico to Uruguay, and an unidentified species from Colombia). If Riodinidae is considered a separate family, all Lycaenidae larvae that eat Bromeliaceae in Latin America belong to the Strymon ziba and S. serapio species groups (Robbins 2010).

Second, the intercepted lycaenid is morphologically similar to North American Strymon larvae. The distribution of body setae matches the figure of Strymon melinus in Peterson (1962: L23) and their morphology agrees with the magnified drawing in Schnitzler et al. (2011: fig. 205). Ballmer and Pratt (1988: tables 1, 2) noted that Lycaeninae lack a honey gland that is present in the Theclinae. The intercepted lycaenid larva from pineapple has this gland as is expected for Strymon and other Theclinae.

Finally, the only reared example we have from port interceptions is a larva from Costa Rica, on Heliconia, sent in by C. Olsen in 2005. The single adult was determined by R. Robbins as S. megarus (USNM lot 0508026). Although not from pineapple, it demonstrates that ports do intercept Strymon from Costa Rica. The bright red color of the reared larva on Heliconia matches the specimens from pineapple illustrated in color by Coto and Saunders (2004). The related Strymon ziba normally is reared from Heliconiaceae and Haemodoraceae, thus Robbins (2010) considered the above host association for S. megarus as needing confirmation. There have been many lycaenids intercepted from Heliconia at United States ports from Mexico to South America, especially from Costa Rica. Current knowledge would suggest most of these should be S. ziba, but without rearing or molecular studies, this shows the complexity of trying to evaluate port interceptions. There is a need to rear more of these Heliconia feeding Lycaenidae.

Identification authority (Detailed)

It seems relatively safe to use the name Strymon for lycaenid larvae on pineapple from Latin America that have relatively unmodified body setae and a honey gland on A7. One example of many interceptions from Philadelphia has the dorsum of A7 darkly pigmented. It is unclear if this is variation or another species. Living larvae can be cream, green, or bright red or pink (Coto and Saunders 2004, Robbins 2010).

The presence of a riodinid, Napaea eucharila, on pineapple is cause for concern. There are many species in this group with unknown larvae, some of which could eat or stray on pineapple. The larva of N. eucharila was illustrated by DeVries (1997: fig. 42). It is a leaf feeder with much longer hairs than Strymon.

If there are no determined Strymon larvae in the port collection, use our figures or those of S. melinus in Peterson (1962) for comparison. Anything that does not match Strymon should be left at family. In most cases, caterpillars of Strymon eat flowers and fruits, but larvae of S. megarus and S. ziba may also bore into leaves when flowers and fruits are unavailable (Robbins 2010). Strymon is a large genus and we normally cannot recognize the larvae outside of two exceptions. If the host is Bromeliaceae from Latin America, Strymon sp. may be justified on a case by case bases. The number of possible species quickly grows if the host is not pineapple. If the larva is on beans from the New World, S. melinus is a possibility.

LYCAENIDAE  -  Strymon

Origin records

Strymon have been intercepted from the following locations:

Brazil, Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Panama

Host records

Strymon have been intercepted on the following hosts:

Ananas comosus, Ananas sp., Annona cherimola, Bromeliaceae, Chenopodium album, Chenopodium ambrosioides, Dendrobium sp., Heliconia sp., Heliconia spectabilis, Phaseolus vulgaris, Pithecellobium dulce, Punica granatum, Zea mays

Records for Annona cherimola, Chenopodium album, Chenopodium ambrosioides, Dendrobium, Heliconia, Phaseolus vulgaris, Pithecellobium dulce, Punica granatum, and Zea mays need confirmation. See the Detailed Information tab for a discussion of Heliconia-feeding Strymon.

LYCAENIDAE  -  Strymon

Larval Skin

Because primary setae are not evident in lycaenid larvae, we include a photograph of a slide-mounted larval skin instead of a setal map below:

Strymon larval skin (slide-mounted)