Sperm Competition

Multiple matings are common in many insect species. The occurrence of remating under natural conditions can be determined by observing the mating behavior of individual females or by dissection to establish the amount of ejaculate or the number of spermatophores present in the female's sperm storage organs. Some of the best documentation of remating comes from studies of many Lepidoptera, in which part of each spermatophore persists in the bursa copulatrix of the female throughout her life...

Imaginal or adult phase

Decticous Pupa

Except for the mayflies, insects do not molt again once the adult phase is reached. The adult, or imaginal, stage has a reproductive role and is often the dispersive stage in insects with relatively sedentary larvae. The imago that emerges (ecloses) from the cuticle of the previous instar may be capable of reproduction almost immediately or a period of maturation may precede sperm transfer or oviposition. Depending on species and food availability, there may be from one to several reproductive...

Structure of the gut

Cicada Foregut Valve

There are three main regions to the insect gut (or alimentary canal), with sphincters (valves) controlling food fluid movement between regions (Fig. 3.13). The foregut (stomodeum) is concerned with ingestion, storage, grinding, and transport of food to the next region, the midgut (mesenteron). Here digestive enzymes are produced and secreted and absorption of the products of digestion occurs. The material remaining in the gut lumen together with urine from the Malpighian tubules then enters the...

Box 42 Reception of communication molecules

Tripectinate Antenna Insects

Pheromones, and indeed all signaling chemicals (semiochemicals), must be detectable in the smallest quantities. For example, the moth approaching a pheromone source portrayed in Fig. 4.7 must detect an initially weak signal, and then respond appropriately by orientating towards it, distinguishing abrupt changes in concentration ranging from zero to short-lived concentrated puffs. This involves a physiological ability to monitor continuously and respond to aerial pheromone levels in a process...

Box 55 Eggtending fathers the giant water bugs

Care of eggs by adult insects is common in those that show sociality (Chapter 12), but tending solely by male insects is very unusual. This behavior is known best in the giant water bugs, the Nepoidea, comprising the families Belosto-matidae and Nepidae whose common names -giant water bugs, water scorpions, toe biters - reflect their size and behaviors. These are predators, amongst which the largest species specialize in vertebrate prey such as tadpoles and small fish, which they capture with...

Diversity In Genitalic Morphology

Aedeagus Female Organ

The components of the terminalia of insects are very diverse in structure and frequently exhibit species-specific morphology (Fig. 5.5), even in otherwise similar species. Variations in external features of the male genitalia often allow differentiation of species, whereas external structures in the female usually are simpler and less varied. Conversely, the internal genitalia of female insects often show greater diagnostic variability than the internal structures of the males. However, recent...

Mating in katydids and crickets Orthoptera Tettigoniidae and Gryllidae

Spermatophylax

During copulation the males of many species of katydids and some crickets transfer elaborate spermatophores, which are attached externally to the female's genitalia. Each spermatophore consists of a large, proteinaceous, sperm-free portion, the spermatophylax, which is eaten by the female after mating, and a sperm ampulla, eaten after the spermatophylax has been consumed and the sperm have been transferred to the female. The illustration shows a recently mated female Mormon cricket, Anabrus...

Lifehistory Patterns And Phases

Embryonic Development Insect

Growth is an important part of an individual's ontogeny, the developmental history of that organism from egg to adult. Equally significant are the changes, both subtle and dramatic, that take place in body form as insects molt and grow larger. Changes in form (morphology) during ontogeny affect both external structures and internal organs, but only the external changes are apparent at each molt. We recognize three broad patterns of developmental morphological change during ontogeny, based on...

The Thorax

Notum Pronotum Insect Image

The thorax is composed of three segments the first or prothorax, the second or mesothorax, and the third or metathorax. Primitively, and in apterygotes (bristletails and silverfish) and immature insects, these segments are similar in size and structural complexity. In most winged insects the mesothorax and metathorax are enlarged relative to the prothorax and form a pterothorax, bearing the wings and associated musculature. Wings occur only on the second and third segments in extant insects...

The estimated taxonomic richness of insects

Surprisingly, the figures given above, which represent the cumulative effort by many insect taxonomists from all parts of the world over some 250 years, appear to represent something less than the true species richness of the insects. Just how far short is the subject of continuing speculation. Given the very high numbers and the patchy distributions of many insects in time and space, it is impossible in our timescales to inventory count and document all species, even for a small area....

The fat body

In many insects, especially the larvae of holometabolous groups, fat body tissue is a conspicuous component of the internal anatomy Figs 3.7 amp 3.15 . Typically, it forms a white or yellow tissue formed of loose sheets, ribbons, or lobes of cells lying in the hemocoel. The structure of this organ is ill-defined and taxonomically variable, but often caterpillars and other larvae have a peripheral layer of fat body beneath the cuticle and a central layer around the gut. The fat body is an organ...

Maxilla

Bee Head Frontal Glossa

LABIUM WITH ' lt gt HYPOPHARYNX each consisting of a basal part composed of the proximal cardo and the more distal stipes and, attached to the stipes, two lobes - the mesal lacinia and the lateral galea - and a lateral, segmented maxillary palp, or palpus plural palps or palpi . Functionally, the maxillae assist the mandibles in processing food the pointed and sclerotized lacinae hold and macerate the food, whereas the galeae and palps bear sensory setae mechanoreceptors and chemoreceptors...