WHAT I EXPECT YOU TO KNOW BEFORE TAKING ENTO 305
There are a few things that I expect you to know prior to taking ENTO 305. I consider this to be essential background information for the topics that I cover in this course. Some are simple things that you learned in elementary school, high school, discovery channel, etc. Others are covered in virtually every introductory course in our department (though I am aware that some of you may not have had any of these courses). The purpose of this section is to inform you of my expectations in this regard, and provide assistance as to how to acquire the necessary information should you lack it. In all cases, should you have any questions, please come see me. I will be happy to give you additional information or references, and discuss in detail any specific item relative to your needs or interests.
Insects belong to the Phylum Arthropoda (the arthropods). The arthropods are usually divided into four subphyla (we will cover this aspect of classification towards the end of the course). On page 100 of your textbook, these subphyla are listed as Trilobita, Chelicerata, Crustacea, and Atelocerata. Insects belong to the Class Hexapoda in the Subphylum Atelocerata. The orders of insects are listed on pages 152-154 of your textbook, and there’s a brief discussion of the classification and relationships on pages 154-156.
In ENTO 305, we will be comparing the morphology of many different insects (and other arthropods), and I will be constantly referring to ordinal names (either by their common name or their more formal ordinal name). I will provide figures or descriptions of those orders that are not commonly encountered, but I will not take time in class to explain the following orders, which I expect you to know already. Page numbers refer to the relevant chapters in your textbook, to give you some additional information should you so desire, but for Ento 305, I am interested only in making sure you have name recognition of what these animals are when they are mentioned in lecture.
Collembola: springtails (pp. 170-174)
Thysanura: silverfish (pp. 179-180)
Ephemeroptera: mayflies (pp. 181-191)
Odonata: dragonflies and damselflies (pp. 193-207)
Orthoptera: crickets and grasshoppers (pp. 209-225)
Dermaptera: earwigs (pp. 234-237)
Isoptera: termites (pp. 252-258)
Mantodea: mantids (pp. 260-261)
Blattodea: roaches (pp. 263-267)
Hemiptera: bugs, cicadas, whiteflies, scales, aphids (pp. 268-329)
Thysanoptera: thrips (pp. 333-339)
Phthiraptera: lice (pp. 356-363)
Coleoptera: beetles (pp. 365-466)
Neuroptera: lacewings, antlions (pp. 469-479)
Hymenoptera: bees, wasps, ants (pp. 481-555)
Lepidoptera: butterflies and moths (pp. 571-643)
Siphonaptera: fleas (pp. 648-661)
Diptera: flies (pp. 672-743)
II. Basic insect development and types of metamorphosis
These topics are covered on pages 39-50 of your textbook. I do not expect you to know or remember any of the details on pages 39-43, but rather some of the basic facts of development that are covered on the following pages. For example, most insects lay eggs; embyonic development takes place in the egg; the eggs hatch into immature stages that are variously called nymphs, larvae, or naiads; these immature stages go through a varying number of molts before the adult stage is reached. In winged insects, there are no further molts after the adult stage is reached, unlike the some other arthropods such as female tarantulas, lobsters, and crabs. Development between egg and adult may occur gradually, with each molt producing a somewhat larger but essentially similarly looking immature (simple metamorphosis) or there may be dramatic changes in appearance between the larval and adult stage (complete metamorphosis or holometabolous development, which includes a pupal stage). You should definitely read the sections on postembryonic growth, metamorphosis, simple metamorphosis, complete metamorphosis, and variations in life history if you haven’t had much prior exposure to this kind of information. It is important to remember that when we talk about difference in structures in ENTO 305, we are usually referring to the adult insect. For example, the labium of an adult grasshopper is very different from the labium of an adult fly. However, we can also talk about the changes in morphology that take place during development. Thus, there is little change in the labium of the grasshopper during development since the structure is basically the same after each molt. However, the labium of the immature fly is very different from that of the adult fly, at least for those flies in which a labium can even be identified in the immature stage.
III. Major pieces of the insect integument
The integument (or body wall) of an arthropod is composed of several layers, and knowledge of the structure of the the integument is essential to understanding how it functions. You should already be familiar with the fact that the body wall is composed largely of cuticle that is secreted during each molting cycle by an underlying cellular layer called the epidermis. The cuticle is made up of long chains of a polysaccharide called chitin, embedded in a protein matrix. Although new cuticle is initially soft after it is secreted (and called procuticle), chemical modification of the protein matrix results in hardening (and darkening) of the cuticle, a process call sclerotization. Differential sclerotization produces a body wall in which some parts are hard while others (especially around the joints) remain soft and pliable. As shown in Fig. 2-2 (p. 6 of your textbook), there is also differentiation of the cuticle from the outermost layer to the innermost. In this regard, you should already know the differences between epicuticle, exocuticle, and endocuticle. If not, please read pp. 6-7.