Insect Reproduction and Development

Transcription

1 Insect Reproduction and Development 1. Identify reproductive stages of insects 1.1. Compare male and female Drosophila, Romalea and Phthyrus pubis. How can you distingusih between the sexes? 1.2. Identify the different lifecycle stages for ants, honeybees and termites. 2. Examine the gamete development in males Examine slides of the grasshopper testes, in order to identify the different stages of spermatogenesis. Identify the apical end of the testis and the region where the testis joins with the vas deferens. The apical end is round and packed with cells, while the opposite end is a more open cavity lined with formed sperm. Identify the individual compartments of the testis, known as cysts. The cysts are separated by connective tissue walls or septa. At the apical end, the cells are grouped into presumptive germ cells known as spermatogonia. These cells are undergoing mitosis and are giving rise to all of the remaining germ cells in the testis. Moving from the spermatogonia in the apical end to the vas deferens at the opposite end of the testis, the cells mature as a group. That is, all of the cells within a given cyst will be in the same approximate stage of meiosis. A good longitutinal section will have nearly all of the stages of meiosis displayed on one section, but you may have to examine several slides to observe all of the stages. Identify the spermatogonia, 1ary and 2ary speratocytes, spermatids and sperm. Grashopper testes (microsructure, low magnification). Individual cysts found in the circle.

2 3. Recognize immature stages and lifecycles: 3.1. There are slides of insects and live specimens in various stages of metamorphosis such as Drosophila, Culex and termites.. Make sure that you observe the different developmental stages and assign the insects to one of the four basic types of metamorphosis: A) Ametabola = no or very simple metamorphosis This division includes four orders of small wingless insects: the Diplura, the Thysanura, the Collembola, and the Protura. The young hatch from the egg with the adult form of body; they differ from the adult only in their size and their sexual immaturity. B) Hemimetabola = incomplete metamorphosis Orders within the Pterygota with a mode of development that includes three distinct stages: the egg, naiads, and the adult stage, or imago. These groups go through gradual changes; there is no pupal stage. The nymph often somewhat resembles the adult stage but lacks wings and functional reproductive organs. C) Paurometabola = gradual metamorphosis Orders of the Pterygota, such as the Hemiptera or Orthoptera where eggs hatch into larval instars called nymphs which generally start with wing pads that develop into fully mature wings. D) Holometabola = complete metamorphosis Pterygote insects that pass through an egg stage, followed by several larval stages, a pupa or transformational stage and finally an adult Match the following diagrams with the four different types of metamorphosis and label the different components of development accordingly.

3 3. Describe and note changes between the different types of metamorphosis by answering the following questions:

4 Which of the above lifecycles have winged adults? What does that tell you about the general taxonomic associations of the lifestyles? How do you distinguish between naiads, nymphs and adults? How do the holometabolous larvae resemble the adults? How do they differ? Do the holometabolous larvae contain wingpads or wings? What a differences and similarities between larvae and pupae? What distinguishes a nymph, a naiad and a larva?

5 4. Raising butterflies, preying mantis and damselflies nymphs. 1. Brassica butterfly We will have set up the brassica plants the week before. Place the paper strip with eggs gently on a leaf and watch the tiny green caterpillars eat and grow. Move the larger caterpillars to brussels sprouts or to other readily available vegetables from the brassica family until the pale green chrysalids are formed. Attractive, white butterflies will appear in about 30 days.. The brassica plants will be required for the caterpillars to use as nutrition and need to be maintained for that purpose. 2. Mantis eggs Place the egg case(s) inside the habitat, remembering to close the habitat door. Keep the habitat temperature at F (22 26 C). If the temperature oscillates or does not remain near optimum, it can take longer for the nymphs to emerge. Mist the habitat once a day (or as needed when the habitat becomes dry) with room-temperature spring water. Do not use tap water or distilled water. Do not allow the spray bottle or water container to come into contact with any soap or detergents. Hatching can take 2 to 8 weeks at optimal temperatures. Each egg case can have nymphs that will emerge all at once. Mortality is high in the early stages of development and during the molting process. Feed flightless fruit flies to the nymphs for the first few months of life, starting 1 to 2 days after emergence. Feed every other day for the first 2 to 3 months. Mantis nymphs will begin to attack and consume their siblings after about a week unless they are divided into individual containers and maintained separately. Continue to mist the habitat daily or place a watering station (shallow dish with sponge or cotton balls) inside the habitat, as the nymphs will actively seek and drink water. Change the water daily because fruit flies will also be attracted to the water source and will foul it. After the mantis has completed its 5 th molt, supply cricket nymphs as a food source. Wait until after the 7 th molt to provide adult crickets as food because a strong cricket can easily attack and kill a mantis. The mantis life span can be a few days to 6 months, as the mantis requires 7 to 9 molts to reach adult size. 3. Damselfly nymphs Damselfly and dragonfly nymphs are cannibalistic, so keep them separate in aquaria or small jars of springwater. Include some aquatic plants or sticks that extend above the water line, as the nymphs will need to crawl out of the water to emerge as adults. The nymphs keep satisfactorily at 10 to 31 C (51 to 87 F). Do not place them in direct sunlight. Damselflies should be fed Daphnia.