Unit Four Insects

Unit IV Insects A major portion of the information for this unit was obtained from “The guide to the Common Aquatic Invertebrates of the Loxahatchee Basin” by Carlos L. de la Rosa, Ph.D. and Carlos A. de la Rosa

On the cutting edge… Scientists at Brooker Creek Preserve are on the cutting edge of science using biological indicators to survey the health of the ecosystem and its watershed area. In addition to using the latest electronic sensors to measure water quality, scientists can verify their results by studying the health of biological indicators. In this case, by looking at aquatic insects in the various preserve habitats, researchers can tell if the food webs are still intact.

Aquatic Insects

Lesson Objectives: Students will be able to do the following: • Categorize aquatic insects with regard to their habitat • Describe the functional trophic groups of aquatic organisms • Distinguish between complete and incomplete metamorphosis

Key concepts: insect, macrohabitat, microhabitat, functional trophic group, complete metamorphosis, incomplete metamorphosis

Insects and their Habitats

Insects are one of the largest abdomen mainly functions in groups of organisms on earth. Only digestion, respiration, and about one million species have been reproduction. Insects also have a identified of the one billion estimated tough exoskeleton that protects them to exist. Their three distinct body from natural enemies and extreme regions, six legs, changes in environmental conditions. and sometimes wings identify Insects have interesting internal insects. The three adaptations designed to suit their body regions lifestyles. For instance, insects have include: the head, open circulatory systems that allow the thorax, and the blood to move around inside the abdomen. The head contains the body cavity without being enclosed mouthparts and most of the sensory in blood vessels. This helps to more organs. The thorax provides the efficiently distribute oxygen and attachment area for the three sets of nutrients to all body parts. Insects legs and if present the wings. The breathe using openings on the body

Project Oceanography 55 Fall 2001 Unit Four Insects called spiracles. Air enters the body Aquatic insects make their homes through these holes and is near or in water. The places where distributed throughout the insect’s these organisms live are body. Insects that eat have digestive called habitats. Aquatic systems that are long tubes divided habitats can be divided into into parts for different functions. The two categories based on insect nervous system transports size. Aquatic information from the sense organs macrohabitats are large, complex such as the antennae and eyes to areas such as oceans, lakes, and the brain for processing. Other ponds. Aquatic microhabitats are information is processed at nerve much smaller environments such as centers throughout the body. the single blade of a submerged plant. Microhabitats are the specific places where individuals of a particular species or group prefer to live. There are many microhabitats within a larger system. They can be described in relation to the water itself. For instance, the water habitat can be divided vertically or horizontally.

Looking at the water from top to Insects can also be categorized and bottom, we discover three distinct classified in other ways. Scientists microhabitats: the classify organisms by studying surface, the water similarities and differences in their column, and the appearance (including shape, size, benthos or bottom color, etc.) They also study community. The water behaviors, life cycles, and other surface is home to insects characteristics. For instance, insects adapted to living on the layer can be divided into two large groups: between air and water such as the those found in aquatic environments water striders, or those using the and those found in terrestrial surface from below to breathe like environments. These large the mosquito larvae. Still others may categories can continue to be live half in and half out of the water divided until we have insects that are like some of the beetles. The water similar in many column itself is a busy place. Insects ways. In this and many other organisms like fish program, we will are found in the water column. focus on the aquatic Nutrients that are food for the insects insects and learn about are found here as well as pollutants. some of their These materials travel through the distinguishing characteristics and system as the water circulates. behaviors. Insects may also be carried along

Project Oceanography 56 Fall 2001 Unit Four Insects with the water flow from one place in Aquatic habitats can also be divided the water column to another. The along horizontal lines. Scientists bottom or benthos provides study the distribution of insects from additional habitat for some insects. the shore through the splash zone, They make their homes in the muddy to the deeper water zones. Who and or sandy bottom sediments or use what lives within them can help materials such as roots and rocks for characterize these areas. homes.

Aquatic Insect Adaptations

Insects have successfully used their the water. Aquatic insects adaptations to completing portions of their life colonize all cycles in or on the water have environments even developed some interesting the ocean. Using adaptations to solve their breathing their wide variety of problems. For example, mosquitoes body forms, sizes, and behaviors breathe through tubes that they has helped specific species inhabit place on the water surface, and unique microhabitats. For instance, aquatic beetles carry bubbles of air some insects have combined their with them under their wings. small size with their ability to fly. This Some aquatic insects have life allows them to escape from enemies stages adapted to and spread to new environments complete aquatic where they can find adequate living, such as the amounts of food and protection. mayfly. Mayfly larvae Other species have wide actually have gills distributions, short life spans, or and obtain oxygen numerous offspring to help increase directly from the water. Damselflies the odds of successfully exhibit similar adaptations. completing their life cycles. In this section, we will take The wings and legs of aquatic a closer look at some of insects are adapted for various types the adaptations for of locomotion. Efficient wings propel breathing, moving, eating, predatory insects such as and reproducing that have helped damselflies and dragonflies through aquatic insects thrive in their chosen the air to catch their prey. They habitats. display incredible speed and agility in the air. Other aquatic insects Insects need to breathe in order to perform aerial acrobatics during their supply their bodies with oxygen. mating rituals. Aquatic insect legs Without oxygen insects would die. are adapted for swimming or Most insects obtain oxygen directly grasping. The water boatman uses from the atmosphere, because they its pair of oar-like legs to “paddle” evolved on land and then colonized through the water while water

Project Oceanography 57 Fall 2001 Unit Four Insects striders stay afloat due to surface larvae have a large pair of jaws with tension and specialized structures on teeth on the end that folds under the tips of their legs. Mayflies have their mouthparts. This apparatus adaptations for living in rocky and called the labium looks like an extra fast running streams. These arm and is designed to grab and adaptations include flattened bodies hold their prey and place it close to and strong claws for hanging on. the mouth of the larvae. Dragonflies emerging from Trophic functional groups identify the eggs laid in or near mode of eating. These include the water use the scrapers, shredders, engulfers, and claws on their feet piercers. Scrapers, such as some to crawl onto mayflies, are plant eaters with plants. specialized mouthparts adapted for removing algae from the surface of Feeding adaptations can be submerged plants and other categorized according to what the surfaces. Water mites and some insect eats and how the insect eats. chironomid larvae are examples of Groups based on what insects eat shredders. These include herbivores, detritivores, insects break apart and carnivores. Herbivores eat decomposing leaves plant material. Detritivores eat dead into smaller pieces plant tissues and other organic and eat them. matter. Carnivores eat other Engulfers, such as the organisms. Aquatic insects that are water beetle, are carnivores are also known as predators that eat their prey whole or predators, because they hunt their in chunks. Piercers have a food. The water strider is a predator proboscis used to suck the juices that eats prey that fall onto the water from their prey. Filter feeders eat fine surface. It uses its sensitivity to detritus or decomposed material motion and water vibration to locate that they collect from the water. its food. It grabs its Many of the insects feeding in this prey, stabs it with its fashion including some caddisfly and sharp beak, and sucks chironomid larvae either have its juices dry. In turn, specialized structures in their bodies predators of the water to collect detritus or build tiny nets in strider such as birds which to capture these minute and fish take particles. advantage of the fact that the water strider cannot detect Reproductive motion above or below the water adaptations are surface. Even the larval stages of critical for the some aquatic insects are adapted for survival of any predatory lifestyles. For example all organism. Aquatic insects have of the dragonfly and damselfly found a variety of adaptations useful

Project Oceanography 58 Fall 2001 Unit Four Insects for the successful completion of their primarily for mating. Many adults do life cycles. These adaptations not even feed and die a few hours include reproducing large numbers after mating. Additional information of offspring relatively quickly and about life cycles and reproduction having adult stages of short duration will be found in the following section.

Life Cycles

Aquatic insects have developed life takes about a month. The adult strategies that allow female, after having a blood meal, them to adapt to lays tiny white eggs in standing or ever changing slow moving water. Within a week seasonal the eggs hatch into larvae that conditions in breath through tubes that extend which they must above the water surface. The reproduce enough primary purpose of the larvae is to offspring to carry eat and grow. They eat things that on the species. One of these float in the water and in some strategies is a metamorphic life species may even eat each other. As cycle. Metamorphosis means to the larvae grow, they go through change in appearance. Just as several changes to prepare metamorphic rock is a rock that has themselves to become changed from one form to another, adults. During this so insects metamorphose or change time, they molt or shed form during their life from larvae to their outer covering, as adults. The life cycles of many changes take place. aquatic insects is split between land After this process the and water. Insects have learned how larvae stop eating and to complete all portions of their life become pupae. Pupae cycle in water except the mating and continue to live near the water reproductive processes. surface using breathing tubes for oxygen. After a few days, the pupae The metamorphic process can be swims to the surface, the pupal skin described as complete or splits open and the adult emerges. incomplete. During complete These adults search for mates. After metamorphosis the insect develops mating the female adults lay their through the following four eggs in the water and die and the stages: egg, larvae, pupae, cycle begins again. and adult. Mosquitoes are an example of an Other insects develop through aquatic insect that has a incomplete metamorphosis. complete metamorphic life During this life cycle, the insect cycle. The complete life develops through egg, larval or cycle of the mosquito nymph stages, to the adult. The

Project Oceanography 59 Fall 2001 Unit Four Insects nymphs are similar in appearance to than the adult. Dragonflies, the adults though they do not have damselflies, mayflies, and true bugs wings and may be colored differently all have this type of life cycle.

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Activity: Insect Observation

Taken from The Guide to Common Aquatic Invertebrates of the Loxahatchee Basin by Carlos L. de la Rosa, PhD. and Carlos A. de la Rosa

Scientists study insects to find out more about their ecological importance and to classify them. By classifying insects, researchers can compare different types of insects according to their behaviors and physical characteristics. By studying their importance within the environment, researchers learn how to control pest species and how to use other insects as natural pesticides.

Objectives: Students will be able to construct apparatus to use in collecting and observing aquatic insects.

Materials: Materials required for each student or each student group. • 2 pieces of glass with sanded or rounded edges • One can of play-dough • PVC pipe or old coffee can (bottom removed), or bucket (bottom removed) • Transparent covering (plastic bags can also be used) • Rubber band • Masking tape

Procedure: Mini-aquarium Construction 1. Form a U-shaped sausage of play-dough. 2. Press the two pieces of glass against the play-dough, one on each side. 3. Fill it with water. 4. Place an organism in it. 5. Observe the organism.

Aquatic periscope Construction 1. Use the piece of PVC pipe, coffee can, or bucket as the base. 2. Make sure any sharp edges are covered with masking tape. 3. Cover one end of the cylinder with transparent plastic. 4. Use the rubber band to hold the plastic in place. 5. Place the end of the periscope into the water and look into the periscope. 6. Observe the water habitat. Identify insects using the attached sheet. 7. Have fun.

Possible Extensions: 1. Have students record the types of organisms they collect. 2. Have students devise a classification system for their organisms. 3. Have students determine what adaptations they found for locomotion and feeding.

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Activity: Tools of the Trade Information taken from The Guide to the common Aquatic Invertebrates of the Loxahatchee Basin by Carlos L. de la Rosa, PhD. and Carlos A. de la Rosa.

Entomologists study insects. You can be an amateur entomologist by using some tools of the trade. Most of these can be made or found in your home.

Objectives: Students will be able to collect and observe insects using readily available materials.

Materials: • Collecting and observation tools (see lists below) • Observation recording tools (paper, pencil, computer, etc.)

Procedure: 1. Discuss various types of collection apparatus and how certain apparatus are designed for particular purposes. 2. Compare some of the professional apparatus with the homemade versions. 3. Discuss steps used by scientists during the collection, observation, and recording process. 4. Have students collect insects and record observations. 5. Discuss the types of information obtained from the activity and why it would be important to have this type of information.

Possible Extensions: 1. Visit a local entomologist. 2. Visit a local business to learn more about the importance of insects in our daily lives. (Places to visit could include a local zoo, botanical garden, butterfly house, crop research facility, pesticide plants, or government entomological research facility.)

Tools for Collecting Tools for Observing • Kitchen strainer • Flat white pan • Small aquarium net • Wide mouth jar • Make a net from a coat hanger • Magnifying lens and an old sock • Forceps Recording Information • Eyedroppers • Locality where collected • Date of collection Professional Collecting Tools • Type of habitat • Artificial substrates • Collection method used • Plankton or drift nets • Kick nets

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Insect Identification

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Student Information: Incredible Insects

All of us have come in contact Only about one percent of all with insects. the insect species are Many of us considered to be pests. These could tell unwanted insects can destroy stories large amounts of crops about pesky resulting in a loss of income for flies and farmers. Other insect pests mosquitoes or carry diseases that can be beautiful butterflies. Insects are harmful to humans or often misunderstood creatures. domesticated animals. Many people are frightened of insects, because they know Scientists have gained useful very little about them. These information by studying insect adaptable creatures are one of adaptations. Researchers the most successful groups of have developed pesticides by organisms on earth watching what insects eat and representing more than 75% of how they eat. Scientists can all animals. They have been also determine ecosystem able to inhabit a wide range of health by studying the insects places from the driest deserts found in a particular place. For to the highest mountaintops. instance, if only one type of insect is found where there Insects are an important part of should be many types, our ecosystem. They help to scientists can use this decompose plants and animals information to find out what is that are then used by other causing the problem. organisms for food. Insects provide us with products such as wax, silk, and honey. They also pollinate many of our crops. Insects can even be used as biological pesticides to control unwanted pests.

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