Leaf structures that arthropods modify Eichrodt 1 Archinsects and Arachnitects : The leaf structures that arthropods c onstruct in the protected a reas of Monteverde Holly Eichrodt Department of Environmental Studies, and Art University of California, Santa Cruz EAP Tropical Biology and Conservation Program, Fall 2016 16 December 2016 ABSTRACT This study aimed to understand which insect and arachnid families manipulate leaves to make shelters and for what purposes they make them I investigated the types of structures they create and how this may benefit their survivorship within three diverse protected areas of Monteverde Estacin Biolgica Monteverde, Bajo del Tigre and Rachel Dwight Crandell Reserve. I collected a total of 56 individuals in the orders Lepidoptera, Araneae, and Orthoptera. I quantified the different types of leaf modifications made as well as the plant family in which they wer e made. I wanted to determine if there was specificity within the different famil ies. The most a bundant family I found was Anyphaeni dae a family of arachnid, and this was the only family collected at all three of my sites. I also found that there were different uses for the leaves which I classified as shelter, feed, molt, pupate, and eggs and I described the refuge that each individual created (by structure and plant family) and compared them. An interesting result is this area houses a unique cricket, which is the one of two families in Orthoptera that spins silk. Furthermore, I did this could be due to insufficient data collected from each family of arthropod especially in the order Lepidoptera. Insectos y araas arquitectos : Las e structuras de hojas constru das por artrpodos en las zonas protegidas en Monteverde RESUMEN El presente estudio tuvo como objetivo comprender qu familias de insectos y arcnidos manipulan las hojas para hacer refugios, y los diferentes tipos de usos que les dan. Investigu los ti pos de estructuras que crean y cmo esto puede beneficiar su supervivencia dentro de tres reas protegidas diversas de Monteverde Estacin Biolgica Monteverde, Bajo del Tigre y Reserva Rachel Dwight Crandell. Coleccion un total de 56 individuos en los rdenes Lepidoptera, Araneae, y Orthoptera. Cuantifiqu los diferentes tipos de modificaciones de hojas hechas as como la familia de plantas en las que fueron hechas. Tambin tuve como objetivo determinar si haba especificidad dentro d e las diferentes familias. La familia ms a bundante que encontr fue Anyphaeni dae, una familia de arcnidos, y sta fue la nica familia encontr en los tres sitios. Tambin encontr que haba
Leaf structures that arthropods modify Eichrodt 2 diferentes usos para las hojas y las clasifiqu como refugio, alimentacin, muda, pupa y huevos, y describ y compar el refugio que cada individuo cre (por estructura y familia de plantas) Un resultado interesante es que esta rea alberga un grillo nico, que es el nico Orthoptera que produce seda. Adems, no enc ontr especificidad de especie en la familia de la eleccin de las plantas de los artrpodos esto podra ser debido al tamao de la muestra tomada de cada familia de artrpodos, especialmente en el orden Lepidoptera. Insects are some of the most creativ e architects, utilizing whatever is at their disposal for protection from predators and weather to increase their chances for survival (Fukui, 2001). Many create refuges through m anipulation of leaves with silk using the silk to create an enclosure. It is understood that some larvae of L epid optera as well as Arachnids use leaf architecture as a means of growth, feeding, or for laying eggs, securing maximum protection (Hanson and Nishida, 2016; Suter et al, 2011). They will modify the foliage to form a shel ter two examples being caterpillar species that roll or fold a leaf in on itself to create a protective feeding tunnel or w eevils that construct complex leaf structures to hide their eggs ( Entomology, 2004 ) M any species of caterpillar are specialized to feed on certain plants since they have evolved the ability to withstand the various chemical defenses Species that do not carr y these chemically defensive traits must avoid predators by making themselves hard er to find. (Hanson and Nishida, 2016). I t migh t be expected to find Lepidoptera species that cannot manage these sp ecialized chemical defenses rely on their larvae to make themselves more discrete through leaf manipulations and only on certain plant types without chemical defenses (Hanson and Nishida, 2016). Some spider species will use silk to construct bends in a l eaf to create optimal protection for behaviors such as laying eggs (Suter et al 2011). For example, t he Clubonia riparia or the leaf curling sac spider create three sided capsules out of a blade of grass or leaf to enclose themselves in this stru cture to lay eggs. (Suter et al 2011). This takes a fair amount of energy from the spider, but it seems to increase security and survival The goal of this study was to investigate the various strategies employed by certain insects and arachnids that create these refuges, and get a better understanding of the benefits and costs of using this energy to construct them Since these structure building behaviors are presumably coded into their DNA, I wonder ed if there was species specificity within family. D o certain arthropods follow the same or similar architectur al patterns within the same family of plants ? Essentially, I wanted to understand what families are the architects of the arthropod world, and what structures they create and why. And furthermore at the different protected areas of Monteverde in varying life zones will there be different species?
Leaf structures that arthropods modify Eichrodt 3 MATERIALS AND METHODS Study Sites I included three sites around Monteverde : t h e trails surrounding the Estacin Biol gica the Rachel and Dwight Crandell Memorial Reserve trails behind the Monteverde Institute and the Bajo del Tigre reserve trails. All three of these areas are protected and belong in a different life zone. The Estacin Biol gica is located in the lower montane wet forest, the Rachel Dwight Crandell Memorial Reserve trails are in p remontane wet forest, and Bajo d el Tigre is classified as premontane moist forest. Data Collection I surveyed each of the three sites for six hours. I cho se a different trail each time I went in to collect data in order to cover a large area. I walked the length of the trail slowly surveying from left to right and when there was a break in t he trail creating an entrance to the woods, I searched in the deeper forested area for ten minutes. I did not spend as much tim e in the woods as the trails I found that leaf structures were more heavily concentrated on the ed ges, and more scattered in dens er foliage. On the trails w hen there were more crowded patches of plants, I would stop an d examine. Otherwise, when spread out, the manipulated leaves were fairly noticeable when moving. Once I finished a trail, I would walk back the way I came, continuin g to examine but at a faster pace, just to make sure that I had not missed an ything and then I would choose a new trail. When I found a leaf that had been modified I remove d it from the plant, taking enough of the plant to be able to identify it to family level, and then place d it in a plastic bag. Once brought back to the lab, I double che cked whether there was an arthropod present using the leaf refuge, took pictures, and t hen described the manipulations to the leaf and the exhibited behavior. I classified the shape of the structure by naming it something that described the form. I then identified t he plant to family level with the help of Eladio Cruz, and arthropod to famil y with help from Emilia Triana for families in the order Araneae, and Kenji Nishida for families in order Le pidoptera and Orthoptera. In my data I also included notes about the plant, how many individuals were u sing the plant (in other homes), and anything else notable about place or behavior. In order to understand the diversity between the three sites, I did a Shannon Wiener Diversity Index test. RESULTS The most abundant family of arthropod architects for all areas is the family Anyphaenidae (21 individuals ) followed by Theridiidae ( 6 ) and the family Pyralidae (6) and then Salticidae (4) (Figure 1) The least abundant families were Bombyc idae (1), Mimallonidae (1), Decophoridae (1) and Scytodidae (1) (Figure 1). The richest order was Lepidopter a (8, not
Leaf structures that arthropods modify Eichrodt 4 Figure 1 N umber of individuals in each family found at all three sites : Estacin Biol gica Rachel Dwight Crandell Reserve trails, and Bajo d el Tigre. I found more individuals in Bajo del Tigre (22), followed by Rachel and Dwight (21) and the least were caught in the Estacin Biol gica trails (13). At Bajo del Tigre and Rachel and Dwight 8 different families were collected, and I collected 6 different families at the Estacin Biol gica (Figure 2). The most abundant family, and found in all three sites, was the Anyphaenidae, and the largest amount of Anyphaenidae were collected in Bajo Del Tigre (9), followed by the Rachel and Dwight (8), a nd last the Estacin Biol gica trails (4 ). Theridiidae, the second most common family found, was only collected at Rachel and Dwight (5), and at the Estacin Biol gica (2). Pyralidae, the third most common and a family of the order Lepidoptera, was only co llected in Bajo Del Tigre (4), and the Estacin Biol gica (2) (Figure 2). 21 6 6 4 4 3 2 2 2 2 1 1 1 1 0 5 10 15 20 25 Number of Individuals Arthropod Family
Leaf structures that arthropods modify Eichrodt 5 Figure 2 The f amilies of ins ects and arachnids collected at all three sites: Estacin Biol gica (Station) Rachel and Dwight Crandell Reserve (Institute) and Bajo Del Tigre 0 1 2 3 4 5 6 7 8 9 10 Number of Individuals Collected Insect/Arachnid Families Bajo Del Tigre Institute Station 1.62 1.64 1.66 1.68 1.7 1.72 1.74 1.76 Bajo Institute Station Diversity Index Site Figure 3. Shannon Weiner Diversity Index for the three sites of Bajo Del Tigre, Rachel and Dwight ( Institute ) and the Estacin Biol gica
Leaf structures that arthropods modify Eichrodt 6 The diversity between sites was not statistically different. The diversity index for Bajo Del Tigre is 1.75, for Rachel and Dwight is 1.74, and for the Estacin Biol gica is 1.67 (Figure 3) The family Anyp h aenidae had 13 individuals who were observed laying eggs which was the most abundant category The arachnid families were more commonly found exhibiting behaviors of shelter Theridiidae (6), Anyphaenidae (6), Salticidae (2), molting Anyphaenidae (2), Salticidae (1), or laying eggs Anyphaenidae (13), Theridiidae (1), Scytodidae (1), and Salticidae (1). For the Lepidopteras, the behaviors exhibited were feeding and pupate. The most common family feeding was Pyralidae (6), where all specimens found wer e displaying this behavior, and the groups that exhibited the majority of pupation were Riodiinidae (2), H esperiidae (2) and the micro Lepidopteras (2) (Figure 4). Figure 4 F amilies of the insect or arachnid and the behavior that they exhib ited in the leaf structure. Displayed below is where the families overlap in terms of leaf structure, and the behavior within the refuge (Table 1). The highest instance of overlap is within the Anyphaenidae family with the next highest overlap is ture for shelter (3). All of the rest of the families either only have one or at most, two overlaps with behavior and leaf structure. 0 5 10 15 20 25 Number of Individuals Shelter Eggs Molt Feed Pupate
Leaf structures that arthropods modify Eichrodt 7 Table 1. The family, the leaf structu re, the behavior, and how many there were in each category. Insect/Arachnid Family Leaf Structure Shelter Molt Eggs Feed Pupate Anyphaenidae Gyro 2 Anyphaenidae Gyro 2 Anyphaenidae Elf Shoe 2 Anyphaenidae 1 Roll 1 Anyphaenidae Elf Shoe 1 Anyphaenidae Pyramid 11 Anyphaenidae Empanada 2 Bombycidae Teepee 1 Decophoridae Small Taco 1 Erebidae Torta 1 Erebidae Loose Tip curl 1 Gryllacrididae One fold 1 Gryllacrididae One fold 1 Hesperiidae Burrito 1 Hesperiidae Teepee 1 Hesperiidae Leaf cap 1 Micro Lep Churro 1 Micro Lep Quesadilla 1 Micro Lep Tiny tip fold 1 Micro Lep Wish bone 1 Mimallonidae Dead leaf shelter 1 Pyralidae Churro 2 Pyralidae Taquito 2 Pyralidae Side Roll (Curl) 2 Riodiinidae Quesadilla 1 Riodiinidae Open Box 1 Salticidae Nachos 1 Salticidae Nachos 1 Salticidae Pocket Fold 1 Salticidae Fern Tunnel 1 Scytodidae Boat fold 1 Theridiidae Which hat 1 Theridiidae Tsunami 3 Theridiidae 1 Roll 1 Theridiidae Fern Tunnel 1 Tortricidae Taquito 1 Tortricidae Quesadilla 1
Leaf structures that arthropods modify Eichrodt 8 T here are a few instances where there are overlaps between insect/arachnid family, plant family, and site (Table 2). Anyphaenidae on Fabaceae occurred at Baj o del Tigre and the Institute, Anyphaenidae on Rubiaceae occurred both i n Bajo del Tigre and the Estacin Biol gica, Anyp haenidae on Solanaceae at Bajo d el Tigre and the Institute, and same for Anyphaenidae on Lauraceae. The only overlaps a mong place and plant family occurred for the family Anyphaenidae. The overlap for arthropod family and plant family was slim as well. Individuals from the family Anyphaenidae were recorded u sing the plants from the family Solanaceae (4), and Rubiaceae (3). In the order Lepidoptera, the only overlap occurred with individuals utilizing Rubiaceae (2). Table 2. Overlap of the family, the plant family in which the y created the leaf structure and site. Insect/Arachnid Family Plant Family Bajo d el Tigre Rachel and Dwight Estacin Biolgica Anyphaenidae Myrsinaceae X Anyphaenidae Asclepiadaceae X Anyphaenidae Acantaceae X Anyphaenidae Asteraceae X Anyphaenidae Fabaceae X X Anyphaenidae Rubiaceae X X Anyphaenidae Salicaceae X Anyphaenidae Piperaceae X Anyphaenidae Solanaceae X X Anyphaenidae Timeliaceae X Anyphaenidae Capriforliaceae X Anyphaenidae Lauraceae X X Anyphaenidae Sapotaceae X Bombycidae Rubiaceae X Decophoridae Lauraceae X Erebidae Araceae X Erebidae Solanaceae X Gryllacrididae Piperaceae X Gryllacrididae Rubiaceae X Hesperiidae Malvaceae X Hesperiidae Rutaceae X Hesperiidae Araliaceae X Micro Lep Myrsinaceae X Micro Lep Araliaceae X Micro Lep Rubiaceae X Mimallonidae Piperaceae X Pyralidae Asteraceae X Pyralidae Acantaceae X Pyralidae Rubiaceae X Pyralidae Unknown X
Leaf structures that arthropods modify Eichrodt 9 Pyralidae Asteraceae X Riodiinidae Myrsinaceae X Riodiinidae Meliaceae X Salticidae Piperaceae X Salticidae Rutaceae X Salticidae Fern X Scytodidae Piperaceae X Theridiidae Araceae X Theridiidae Piperaceae X Theridiidae Fern X Theridiidae Lauraceae X Theridiidae Rubiaceae X Tortricidae Proteaceae X Tortricidae Araceae X DISCUSSION This study concluded that although there may not be a species specificity of architecture b y family, or plant family us ed, there were clear trends in what kinds of species were crafting their own homes from leaves. Within family especially displayed amo ng the arachnid families, for the different functions they would exhibit, there was a d ifferent structure they would use to accommodate each function The Anyphaenidae family for example constructed many different types of refuges, but all of them were us ed differently the pyramid a cone like structure folded tree times was most likely the species Clubonia riparia (Suter et al, 2011) was always and exclusively utilized for laying eggs. A shelter, classified as the gyro an upturned structure with webbing pulling the center together was most often used for molting Most arachnids post molting are less mobile for a couple days once they shed their exoskeleton, the skeleton underneath is soft and pliable until it hardens ( Overton, 2007). C reating a shelter in order to molt with protection is a good use of energy to ensure survivorship. The more closed structures such as elf shoe were structures that were discrete as they wrapped the leaf into a small horizontal cone sha pe. This was more often used as a shelter. These differences in refuge type could also be determined by the different species that were present within family if I had identified to species level, this could have been understood better. Another family of ar achnids, the Theridiidaes, also had interesting things regarding leaf structure. The di fferences in shape were not drastic, but they appeared different Araceae plant verses a stouter leaf, while the Lauraceae is longer and leaner the way the fo ld was created was very similar, but gave a different appearanc e with a different plant family. For Lepidoptera, there were fewer consistencies with shape this could be due to my small sample size from each family. However, I did notice that for different behaviors pupate and feed, there were similar shapes. For feed, larvae almost always demonstrated a roll structure, wh ile for pupation; they constructed more flat structures with multiple leaves.
Leaf structures that arthropods modify Eichrodt 10 Another thing to note is that the Theridiidae family was collected most abundantly in the Rachel and Dwight ( Institute ) trails, less so at the Estaci n, and then not at all i n Bajo del Tigre I found them at every site, but their webs varied. The individuals collected at the institute (5 ) had their webs solely contained within one leaf while the webs of the individuals found at the station (1) and Bajo Del Tigre (0) expanded t o other leaves. They still utilized a leaf curl for protection, but they had a web that extended down to other leaves or other parts of the plant demonstrating a c lassic Theridiid web structure m eaning a more or less irregular web with strands attached to a substrate below a protective cover of a leaf, rock, or branch (Shapiro, 2014) This kind of structure, that I did not collect or includ e in my data set I also observed in other individuals especially within Bajo del Tigre. There was a type of small orb weaver that utilized a manipulated a leaf or a couple of manipulate d leaves for protec tion. They would build their webs underneath or between the leaves and have the leaves off to the side as a base to take refuge in i f there was danger or something startled it. This type of behavior however I did not observe behind the I nstitute, and seldom in the Estacin trails. My results showed that the richness of arachnid families is lower, but the abundance is fairly high, and the richness of Lepidoptera families is higher, but has a lower abundance. Also for spiders, there are not necessarily family speci ficities to leaf type used this may be more prevalent in the Lepidoptera families even though my data does not show this Fo r example, one of the individuals in the Hesperiidae family is of the species Astrapes augeas and they are only found on plants in the Malvaceae family (Carmona, 2016). Additionally, they are almost always found in a little home that they made for themsel ves in the leaf for protection while they feed (Carmona, 2016). This is one species that was included in my data, and it was found on a Malvaceae. There are many plants that employ chemical compounds for defense against herbivores (War et al., 2012) S o although there was not an explicit trend with insects and their choice of leaves, it is plausible that they chose specific families of leaves for different reasons. If the individual is able to cope with the chemical defense of a plant, then they may not make these structures for they would not need to expend the energy for protection from parasites or other predators I nstead their own chemical compounds would be their defense. ( Gentry and D yer 2002 ). Without a chemical resistance the larvae chose plant s that were less harmful, and they spent the extra energy for protection. According to a study done by Robert Marquis and John Lill, there are likely other structural features of host plants that attribute to an individuals choice of construction site. Thi s had to do with weight of the larva, and differences in nitrogen, nitrogen availability, and protein binding capacity of leaf extracts (Marquis and Lill, 2010). This however, really only pertains to when larvae exhibited the behavior of feeding rather tha n pupating. A l s o explained by my results there was not necessarily a trend or overlap between family of individual and the family of plant that they u s ed for the structure within the three sites. This lack of overlap could be attributed to the fact that there was not a significant amount of individuals collected from all families other than Anyphaenidae. The only overlap that did not occur within the family Anyphaenidae was in Pyralidae with Rubiaceae Another finding, was that in some cases the re were other individuals us ing structures that they did not create. They would take over refuges that the individual who created it abandoned. I found species partaking in this behavior s uch as weevils and other Coleoptera. Another type of indiv idual that I suspect could be deemed a squatter s an old refuge is from the Salticidae family. The two structures that I classified as nacho I believe created
Leaf structures that arthropods modify Eichrodt 11 their own structure since one individual recreated it within th e plastic bag, bu t the ones found in fern tunnel and poc ket fold I expect the individuals were taking over an old refuge for protection as well as means of energy preservation. I did not include those two structures within the data set however because I have no data to support that claim. Another insect that at first, I assumed to be a squatter was a cricket from the Gryllacridae family H owever I learned that they do in f act spin silk to build shelters and are one of two families in this or der that are able to do this (Walker et al., 2012). This type of cricket is known as the Raspy cricket and during the day they retreat to th e leaf shelter they created this has been presumed to be a defense against predation, but it has also been suggested to be a protection from desiccation in dryer areas (Walker et al., 2012). It is important to understand how different arthropod use their environment and understanding how they protect themselves When we understand our environment better, we can connect to it more as well as seek to better conserve it. During this study, there were many things that occurred that I found interesting and surprising but since it is a little understudied, I was not able to explain these occurrences. With more interest in thi s topic, we will be able to understand the behaviors of the many arthropods among us Future Studies In all three sites, I encountered a high quantity of vacant caterpillar refuges. These more often had been used for feeding. However, it made me consider at what point do Lepidoptera deem a leaf unsalvageable when do they move on to another food source? Some it seemed, ate away a good amount of the leaf, while othe rs only depleted a small portion of it. Perhaps this is something that varies with fa mily or species, size, or how close the individual is to pupating. In the future, I would li k e to study this in greater depth Another consideration I would like to look more into is whether the individual, when put under stress, exhibits the behavior it c r eated the shelter for faster for example laying eggs or pupating, or if the disturbance changes the beha vior they would have exhibited, as this is something that could have skewed my data as well. Another aspect that would have been beneficial to focus o n was at which height the specimen was collected from although I could not see easily or reach individuals higher up it would b e an interesting thing to note. Observationally, I found that arachnid individuals were more often higher up and Lepidoptera wer e closer to the forest floor. With more time and resources it would also be interesting to see what architect species are found higher up in the canopy. ACKNOWLEDGEMENTS I would like to thank my advisor Sofia Arce Flores for all her help throughout the entire process, for taking an interest in my project and essentially making it a reality by providing me with all the necessary resources to keep me moving forward. I would also like to thank her baby Abi for always brightening my day with her presence. I would like to thank Emilia Triana for helping me identify my arachnid families and for diminishing my fear of spiders. A special thanks to Kenji Nishida for allotting me som e of his time to identify my insect species and for continuing to keep in touch on the specific species of larvae once reared. I would also like to thank Eladio Cruz for iden tifying my plant families, as this was very helpful. A nd a final shout out goes to all of the
Leaf structures that arthropods modify Eichrodt 12 EAP staff and family for keeping me engaged and in good spirits and to Frank Joyce for making this program and experience possible! LITERATURE CITED Bartlett T, Hyche L. 2003 Leaf Curl/Roll. C armona M. 2016 Astraptes augeas (Hesperiidae). Area de Conservacion Guanacaste Costa Rica Fukui A. 2001. Indirect interactions mediated by leaf shelters in animal plant communities. Population Ecology 43(1). 31 40. Gentry G, Dyer L. 2002. On the conditional nature of neotropical caterpillar defenses against their natural enemies. Hanson P E, Nishida K. 2016. Insects and Arthropods of Tropical America. Cornell University Press, Ithaca, NY. Marquis J, Lill J. 2010. Impact of plant architecture versus leaf quality on attack by leaf tying caterpillars on five oak species. Oecologia 163 (1). Overton M. 2007. How Do Spiders Grow: (Moulting and Regeneration). Burrow. Shapiro, L. 2014 Brief Summary. Encyclopedia of Life Suter B, Miller P, Stratton G. 2011 Egg capsule architecture and siting in a leaf curling sac spider, Clubonia riparia (Araneae: Clubionidae). Journal of Aracnology BioOne. Walker AA, Weisman S, Church JS, Mer rit t DJ, Mudie ST, Sutherland TD. 2012 Silk from Crickets: A New Twist on Spinning. PLoS ONE 7(2): e30408. War A, Paulrai M, Ahmad T, Buhroo A, Hussain B, Ignacimuthu S, Sharma H. 2012 Mechanisms of Plant Defense Against Herbivores. Plant Signaling and Behavior. NCBI.