This order of universally distributed insects is represented by the silverfish , chapter 8 , which are common household pests and are injurious to book bindings, wallpaper, and similar articles containing starch or glue size. Furthermore, insects have a front lip labrum , 1 pair of mandibles, 1 pair of maxillae, and a hind lip labium. . The rigid cuticle inhibits growth, so arthropods replace it periodically by molting. Although currently the order Hymenoptera is third in size from the standpoint of the number of species which have been described and named, probably great numbers of inconspicuous species, especially among parasites, have escaped the attention of taxonomists, so it is likely that there are more species of this order in existence than of any other. The balance of the appendages is legs.
Appearance radically different from that of adult; typically cylindrical. . Wings develop internally as imaginal buds before being everted in the pupa. If the cover slips were not placed on the scale insects after they were bathed in oil, they became desiccated and died much more rapidly; none of them survived for a period longer than 10 days Ebeling, 1945. The lower lip or labium performs a function similar to the lower lip of vertebrates. They first produce new, softer exoskeletons underneath the old ones. There are 11 orders of living arachnids, of which 7 will be considered of more or less importance as household pests, although some are harmless and are of interest only because they may be confused with bona fide pests.
The Lepidoptera are also highly specialized in other ways. Within a phylum there are smaller groups of animals called classes, which also have common characteristics that distinguish them from other groups. . Diapause may be triggered by a engthening vernal photoperiod or by a shortening autumnal photoperiod, or may be imposed by such internal factors as heredity, enzymes, or hormones. Insect blood has no red blood corpuscles and plays no part in oxygen transport, although the plasma of chironomid larvae does contain hemoglobin which may aid in respiration. Suborder Homoptera The suborder Homoptera is characterized by the wings, when present, being membranous, or sometimes with a somewhat leathery texture, but never with the basally thickened forewings hemelytra which characterize the Heteroptera. Four narrow, membranous wings, nearly veinless, fringed with hairs; some species are wingless.
. Insects which lay eggs are said to be oviparous. Other psocids live on the bark of trees and on foliage. Likewise, beginning students and those not familiar with a given insect group are not likely to know the meaning of the majority of the abbreviations. These three pairs of legs are attached to the thorax, as are one or two pairs of wings. In the Arthropoda, the various classes subdivisions of a phylum share these characteristics in common: bilateral symmetry; segmented bodies; paired, jointed appendages; protective cuticle; a dorsal blood vessel; and a ventral nervous system. In the Lepidoptera, the mouthparts of the larvae are always different from those of the adults, the larvae having mandibulate and the adults having haustellate sucking mouthparts.
The nymphs naiads and adults of insects with incomplete metamorphosis live in entirely different habitats. The female places her eggs on the ends of hairlike stalks about 12 mm in length. . Every seta on its surface is useful in communicating information about the spider's surroundings. They operate in a horizontal plane, i. Order Scorpions Like the spiders, scorpions have 2 body regions, the cephalothorax or prosoma, and the abdomen. The 3 orders involved are placed in a separate division of the Exopterygota later in this chapter, but this is not meant to indicate their phylogenetic relationship to other insects.
Primitively wingless insects without metamorphosis. The latter are so called because of their strange gyrations when they circle round and round one another as they swim or skate on the water. However, there is a harmful stage. Thysa nu'ra Abdomen with not more than 6 segments, often terminating in a springing apparatus springtails. . Sclerites and sutures are often used in the taxonomy of Coleoptera because the sclerites are fitted together with remarkable exactness and precision.
Order coleoptera includes beetles and weevils and contains the most species. In some insects, the normal adult morphological features are absent; characters of the immature stage are carried over to the sexually mature and reproducing individuals. The myriapods include the centipedes and millipedes. The anterior part of the cephalothorax bears 3 groups of eyes: a median group of 2 eyes and a lateral group of 2 or 3 eyes at each margin. The spiracles are the external openings of the air tubes, known as tracheae, which divide and subdivide as they penetrate to all portions of the body.
Insects are arthropods with jointed appendages, segmented bodies, and an exoskeleton composed of chitin. Small, narrow, rarely over 10 mm in length, unpigmented because of their secluded and subterranean habits. . The few species in other orders that have only a single pair of wings do not possess halteres. Like all other arthropods, they grow by molting, but they may also increase in length by adding an additional body segment at each molt.
In the United States the principal genus is Tarantula, although it is not a tarantula, which is a large spider. . After their victims are drained of their body juices, they are cast far beyond the borders of the pit. In some spiders, these glands are located entirely within the chelicerae, and in others they extend backward into the first section of the cephalothorax, as diagrammatically illustrated in , chapter 9. .