Mathias Jaschhof – Germany (photos 1-3 by Juan Mata Lorenzen; other photos by MJ)
Gall midges (Cecidomyiidae) are best known for their habit to induce malformations – collectively called galls – on living plants. Many galls are inconspicuous blisters, while others are eye-catching, such as these rambutan-like galls decorating the leaves of Neotropical Miconia trinervia trees (Fig. 1). The galls provide shelter and food for the developing larvae and sometimes even the place for pupation (Figs 2, 3). Apart from plant-feeders, the gall midge family includes fungus-feeders, predators and parasitoids. But not only the diet of gall midges is remarkably diverse.
Many dipterists assume that Cecidomyiidae are the most species-rich family of Diptera. Our present knowledge of Cecidomyiidae taxonomy is so scant, however, that the numbers of species occurring in particular countries or regions are usually regarded as inestimable. In Costa Rica, where fewer than 20 different gall midges have been recorded in the past, estimates range from 2,000 to 18,600 species. So, how many different cecidomyiids would you expect to occur in Zurqui?
To answer this question, the ZADBI project focuses on adult morphology as the only means to identify species – an approach that is widely pursued in insects but not so, previously, throughout the Cecidomyiidae. Admittedly, only few gall midges provide truly conspicuous morphological characters, such as a golden yellow “fur” of scales (Fig. 4) or bicolored antennae and wings (Fig. 5). In fact, at the first (i.e. macroscopic) glance most Cecidomyiidae look alike (Figs. 6-8), even those belonging to different subfamilies (Fig. 7 versus Fig. 8). The body structures in which one species differs from the other are minute and must be studied by compound microscope.
In fungus-feeding Cecidomyiidae it is common-place to identify species on the basis of differences found in the genital structures of males (Fig. 9). ZADBI uses the same kind of characters to distinguish among different species of plant-feeders and predators, all classified in the subfamily Cecidomyiinae (Fig. 10). Moreover, the male genitalia of many Cecidomyiinae from Zurqui turn out to be bizarrely shaped (Fig. 11) – a plethora of morphological diversity that is not yet described!
Back to the question of how many different morphospecies of Cecidomyiidae are present at Zurqui. From August to September 2013 the ZADBI team expended a big concentrated effort to answer that question – and found an amazing 556 different species! This is more species than thus far described from all of Central and South America combined. And: this species number is likely to increase considerably with ongoing study, as half of the Cecidomyiidae specimens collected in Zurqui are not yet identified …
Figs 1-3: Unidentified Cecidomyiinae causing leaf galls on the tree Miconia trinervia in Costa Rica. 1: gall; 2: cross section thru gall with pupa; 3: same pupa, enlarged (sample taken by M. Zumbado, photos: J. Mata).
Figs 4-8: Habitus of male Cecidomyiidae from Zurqui. 4-6, 8: Cecidomyiinae spp.; 7: Porricondylinae sp. (photos: J. Mata).
Fig. 9: Male genitalia of 6 different species of Winnertzia (in Winnertziinae) from Zurqui.
Fig. 10: Male genitalia of 4 different species of Cecidomyiinae from Zurqui.
Fig. 11: Diversity in male genital structures of Cecidomyiinae from Zurqui.
Greg Curler – Purdue University (photos by GC)
Psychodidae (moth flies and sand flies) are a diverse family of flies with six subfamilies, approximately 3,020 described and many undescribed species. Both larval and adult psychodids are variable in their feeding behavior. Some larvae are detritivores feeding on decaying plant tissue, feces or dead snails while others feed on fungi, rotting wood or algae and diatoms. Adult females of many psychodid species feed on the blood of vertebrates such as amphibians, non-avian reptiles, birds and mammals including humans. Other species do not feed as adults, or their feeding behavior is unknown. Some psychodids occasionally cause myiasis (infestation of living tissue by fly larvae) in humans. At least one species transmits parasites among frogs and many transmit agents of human diseases including bartonellosis and leishmaniasis.
Five of the six subfamilies are known to occur in the Neotropical region. Of those five, four have been collected at Zurqui. One of the most remarkable psychodids collected during the ZADBI project is a species of Sycorax that is new to science. This species is of particular interest because it represents the first record of subfamily Sycoracinae for Costa Rica and the northernmost record of the subfamily in the Western Hemisphere. Among the most striking characteristics of all Sycorax species is the wing venation, by which they can easily be identified. Their behavior as adults is also interesting. Females of several Sycorax species are known to feed on the blood of frogs, while both females and males have been found congregating on frogs. It is currently unknown whether females of the new Sycorax species are feeding on blood; however, this is very likely based on its overall similarity to other species known to be blood feeders.
Dalton de Souza Amorim – Universidade de São Paulo, Ribeirão Preto (photo by DSA)
The bibionids are a morphologically and behaviorally interesting group: for example, they fly in copula for hours. This conspicuous behavior often catches the attention of non-specialists as well as of dipterists, and is the origin of the common name of the group, “love-bugs.”
Most remarkable, however, is their morphology. Bibionids often exhibit strong hues of orange and yellow in striking contrast to black. These flies may also display strong sexual dimorphism (males and females appearing different), especially within species of Bibio and Dilophus. Some of the species within these genera, especially females, have bizarre, awkward, and almost alien-shaped heads.
The group is tricky to study. There are only a few genera in the family that can be easily recognized with identification keys. Most genera, however, include dozens of species, but keys for the species-level are still unavailable and so it is not easy, for species outside North America and Europe, to know if they have been previously described.
So far, the bibionids collected from ZADBI (153 specimens caught in Malaise traps) include the three most common genera, Plecia, Dilophus and Bibio, belonging to seven different species. It is too premature at this point to know if any of the seven species are new to science. There are no records for Bibio in Costa Rica (which are uncommon in collections), but species of the genus have been assigned to Mexico, Colombia, and Venezuela. One of the Dilophus species may be D. minimus Hardy, described for Costa Rica. There is another species of Dilophus described from Nicaragua, but there are other records of the genus for Mexico and Colombia. Plecia species have been species described for Costa Rica, Panama, and Nicaragua. A deeper look into the current literature on bibionids will help us reveal if any of the three species of Plecia found so far in Zurqui is new.
Brian V. Brown, LACM (photo by Inna Strazhnik)
An extremely rarely collected phorid fly genus, whose brachypterous (short-winged) females live in the nests and amongst the brood of Pheidole ants, was collected by a ZADBI Malaise trap. This genus, previously known only from Brazil, was first found in Central America last year by biologist Wendy Porras. It is widespread in Costa Rica, Brazil, and presumably in places between. Usually females are located by breaking open Pheidole nests in rotten wood or in carton nests constructed under leaves. Unfortunately, we don’t know what they are doing there, although we guess they lay eggs and the larvae feed on or among the ant larvae. The specimen in the Malaise trap was the first male we have ever seen.
Dalton de Souza Amorim Universidade de São Paulo, Ribeirão Preto (photo by DSA)
Scatopsids compose a small family when compared to other gigantic dipteran groups—33 genera are known for the world, and 62 species described for the Neotropics. Not very common in collections, it was a nice surprise to see in the 14 slide mounted specimens of the family in the first loan coming from ZADBI—eight species from six genera of these tiny flies. The specimens were collected with two Malaise traps in the same site for a period of no longer than three weeks. More interesting, all eight species are new to science, exactly 100%! There are 28 recent species described for Central America and Mexico, plus another three introduced species. The generic content of the specimens of this first loan is also interesting: they come from two of the three subfamilies expected to occur in the area and almost half of the 17 genera that shall have species in the area.
These initial results just confirm my best expectations for the Zurqui project. Traditional taxonomy is group-based, obviously the right approach in most cases. If we want to know, however, the real diversity from a geographical view point, intensive and extensive single site sampling has to be made. There is probably no single spot on Earth for which the real Diptera diversity is known and this project is key in bringing up new answers. At best, raw estimations have been made based on indirect evidence. Diversity for larger areas actually mixes distinct areas of endemism, bringing inadequate estimations. It must be said, finally, that single spot diversity needs directed effort to collect as much of the diversity it can be grasped by different techniques along a certain period across the year, as is being done in ZADBI. This is just an initial sampling and the next loans will bring a clearer picture. Nevertheless, even for a small and considerably unusual group as the Scatopsidae, we have amazing results right from the beginning. (Photo by Dalton Amorim).
Brian V. Brown – LACM (photo by Inna Strazhnik)
Three specimens of the genus Podiomitra, a member of the family Sphaeroceridae and subfamily Homalomitrinae, have been found so far at Zurqui.
Look at the strange head, unusual “feet”, and incredibly reduced wing venation on this fly. Amazingly, we have collected at least three more already in our All Diptera Biodiversity Survey in Costa Rica, all from light traps. It will be interesting to see what other strange creatures are uncovered by our intensive survey of this tropical cloud forest.
Art Borkent – Canada
Expeditions begin with ideas and those ideas always have a history. In our case, there was a remarkable project that began in 1998. In that year, the main institution studying the biodiversity of Costa Rica, Instituto Nacional de Biodiversidad (INBio for short), with the support of the Global Environment Facility of the World Bank, initiated a program to better understand the fauna of Costa Rica. They recognized that it was very difficult to make decisions regarding development if most of the fauna was unknown or couldn’t be interpreted. Knowing what species are present in ecosystems is a vital step in making better management decisions. As a result, they asked a number of scientists in the international community to work on different groups of insects, including the Diptera (true flies). (more…)