Humpback whale — Whale and Dolphin Conservation
- 1 Humpback whale
- 2 Tuneful, graceful and simply, huge, the amazing humpback whales are the virtuosos of the deep.
- 3 Humpback — an intricate insect
- 4 Humpbacked Habitat
- 5 Humpbacked lifestyle
- 6 The appearance of humpbacks
- 7 Humpback development
- 8 Humpback Whale
- 9 Description of the Humpback Whale
- 10 Interesting Facts About the Humpback Whale
- 11 Habitat of the Humpback Whale
- 12 Distribution of the Humpback Whale
- 13 Diet of the Humpback Whale
- 14 Humpback Whale and Human Interaction
- 15 Humpback Whale Care
- 16 Behavior of the Humpback Whale
- 17 Reproduction of the Humpback Whale
- 18 Phoridae
- 19 Related terms:
- 20 Diptera
- 21 Production of Dipteran Parasitoids
- 22 Oral Nematodes (Panagrolaimidae)
- 23 Mites (Acarii)
- 24 Fire Ants
- 25 Enhancement of Biological Control in Annual Agricultural Environments
- 26 Soft Scale Insects their Biology, Natural Enemies and Control
- 27 Physical Transport, Heterogeneity, and Interactions Involving Canopy Anoles
- 28 Parasitoids
Tuneful, graceful and simply, huge, the amazing humpback whales are the virtuosos of the deep.
Singing some of the longest and most complex songs in the animal kingdom, humpback whales are masters of melody. As if that wasn’t impressive enough, they also undertake some of the longest migrations of any mammal in the world.
IUCN conservation status: Least concern
What do humpback whales look like?
Humpback whales are massive, growing to 17 metres in length. Their huge, dark bodies are flanked by enormous pectoral flippers growing up to around a third of their body length. Fantastic tools, they use their highly-manoeuvrable flippers for hunting by slapping the water and for swimming and even possibly regulating their body temperature. Equipped with a giant tail, this is their identifying feature. When they ‘fluke-up’ and dive, researchers can identify individual humpback whales by the markings on the underside of their tails. Moving to their heads and humpback whales are covered in funny knobbles. Unlike Auntie Mildred and more like Sooty the cat, these knobbles or bumps are called tubercles, and contain a single hair acting like a cat’s whiskers. Providing a sensory tool, these hairs feed back information about the whales’ surroundings.
What’s life like for a humpback whale?
A year in the life of a humpback whale is a tale of two halves. Humpback whales are experts when it comes to travelling and devote huge portions of their time to being on the move. With half the year spent in colder, high latitude polar waters like Norway, they use this time to feed and fatten up. Following this period, they then head to warmer, shallow tropical waters, socialising, mating and looking after their young calves. Well-known for their underwater lullabies, male humpback whales are particularly vocal during the mating season. No-one knows for sure why this is but it could be that males are attempting to serenade potential female partners. Covering such huge distances, humpback whales are constantly exposed to a number of threats and must navigate a myriad of life-threatening dangers. These include whalers, fishing nets and ships.
What do humpback whales eat?
Like many other large whales, the prey of humpback whales are microscopic compared to their own bulking mass. Feasting on plankton, tiny crustaceans like krill and other small schooling fish, they gulp enormous mouthfuls of their prey and seawater. Using their baleen plates, they then filter out the water.. As you can imagine, due to their size humpback whales need to eat a lot of prey to survive. In fact, an adult humpback whale can consume up to 1360kg of food each day.
Where do humpback whales live?
Humpback whales are found in all the world’s major oceans. Most populations undertake huge annual migrations, moving between mating and calving grounds in warmer, tropical waters, and feeding grounds in colder, more bountiful waters. Unfortunately, humpback whales were hunted extensively in years gone by, and still are in some places, such as the St Vincent and Grenadine islands in the Caribbean. In some areas, like the north Atlantic, their numbers are thought to be recovering, yet in others, like the north west Pacific, there is still a major cause for concern.
The long-distance travellers
Humpback whales make some of the longest migrations of any whale, travelling thousands of miles each year. In the northern hemisphere, whales feed in the cold waters of northern latitudes before heading south to breed in warmer waters. The same things happens in the southern hemisphere, only in reverse as the seasons are the opposite. It means whales in each hemisphere never meet one another.
Humpback — an intricate insect
Humpbacks are small insects, the main feature of which is the incredibly shaped outgrowths on the back. These outgrowths can take the form of horns, spikes, ridges, balls, and so on.
Outgrowths on the humpback body can be larger than the insect itself. Because of them, the hunchbacks got their name.
There are more than 3 thousand species of these insects. Humpbacked women live all over the world; they cannot be found only in the Antarctic. Most species live in the tropics of South America. In addition, humpbacks are found in temperate latitudes.
There are more than 3000 species of these insects
It is worth noting that in tropical specimens, the outgrowths on the back have more bizarre shapes in comparison with their northern counterparts.
Humpbacks are small insects, the main feature of which is the incredibly shaped outgrowths on the back.
Horned humpbacks live in our country, but their appearance is not so intricate. In Europe, there are only 3 types of humpbacks.
Horny humpbacks live in our country
Most humpbacks live on plants. The most favorite places are the edges and glades in the forests. In most humpbacked women, part of the life cycle takes place on trees.
Although the structures on the humpback bodies can be significant, these insects are able to fly.
Most humpbacks live on plants.
True, they do not fly too well. They can overcome in the air only a few meters.
The life of humpbacks can hardly be called saturated, since most of them do not leave plants. They suck juices from plants. Humpback vegetable juice is the main source of nutrition. Adult insects and larvae feed on them. They cause minor damage to cultivated plants.
Hunchbacks can fly, though very badly.
There are humpbacks from July to August.
The appearance of humpbacks
As already noted, the main feature of this species are interesting outgrowths on the pronotum. In some humpbacks, they are simple, for example, they resemble a horn in shape, while in others they are real architectural structures. The main significance of these outgrowths is not clear, most likely, this is a way of mimicry.
The humpback spends most of his life on the plant
It is noteworthy that in males and females of the same species, the shape and color of outgrowths may differ.
Humpback females lay eggs on the surface of leaves, on the roots of plants, or under the bark. Eggs hibernate. To protect the eggs, many females cover them with a special foamy substance that hardens and becomes quite durable. And some females guard their clutch, in addition, they remain with the larvae until they develop.
Humpback got its name due to the unusual shape of its body.
The excrement of humpback larvae is rich in sugar. These excrement is called honey dew. Ants like this dew very much. In this regard, cooperation between humpback nymphs and ants has been established, useful for both types of insects. Ants feed on sugary matter and, in gratitude, they protect the nymphs from other predatory insects.
For people, hunchbacks are completely harmless
Humpbacks are completely safe for people, although their horns and spikes are sharp and you can prick about them.
Known for their lovely signing abilities, humpback whales are quite charismatic marine mammals. Heavily depleted by whaling, this species has since become a fan favorite on whale watching ships. These fascinating whales have many distinctive characteristics, read on to learn about the humpback whale.
Description of the Humpback Whale
The humpback whale is a large, dark gray, torpedo-shaped marine mammal. These whales are easily distinguished by the “pleats” or grooves along their throats. Though they are not the only species with these grooves, the humpback whale’s white underbelly and distinctive pleats make them easily recognizable. This species also has long pectoral fins on either side of its body, a small dorsal fin on its back, and a large tail fin – known as a fluke.
Interesting Facts About the Humpback Whale
The humpback whale is a unique marine mammal, with a number of distinguishing – and endearing – characteristics. Like many marine mammals, they were heavily depleted during the whaling era, but are now a centerpiece in ecotourism.
- The Whale Watcher’s Sweetheart – Humpback whales are loved by whale watching ships because of their active behavior, and propensity to approach the vessels. Whale-watching ships are heavily regulated, and are not allowed to approach any whale closer than 100 yards. Thus, whales that voluntarily approach ships are highly appreciated, giving tourists a closer look at the huge marine mammals. There is some concern about the implications of this behavior, as time spent approaching ships is time not spent eating, nursing, and socializing with other animals. Scientists are also concerned that whales approaching vessels will be more susceptible to ship strikes.
- Rorqual Whales – The humpback whale is one of nine species in the family Balaenopteridae, which compromises all the animals known as rorqual whales. This group of whales is characterized by the deep grooves in their throats, which expand to fill with water while feeding. Rorqual whale species forage by opening their mouths to take in large amounts of water, allowing their throats to expand like balloons. The whales then spit the water back out of their mouths, filtering out small fish and krill (a small shrimp-like crustacean) through plates of baleen.
- The Songster of the Sea – Humpback whales have some of the most recognizable vocalizations of all whale species. Male humpback whales produce lengthy, organized songs that have distinct melodies. Researchers believe that humpback whales may sing while searching for a mate, or establishing dominance. Populations of humpback whales in different locations have different songs, for example, the North Pacific population has one song, while the North Atlantic population has an entirely different one. These songs gradually change from one year to the next.
- Bubble Nets – Humpback whales use a unique feeding method to capture fish. Groups of humpback whales will dive below the fish and blow bubble “nets” to corral them into one area. The whales then lunge through the trapped fish, taking large mouthfuls of fish and water to filter through their baleen.
Habitat of the Humpback Whale
Humpback whales spend different times of year in different habitats. They spend summer in northern latitudes, and migrate to tropical waters near the equator during the winter. There is also a population of humpback whales that remain in the Arabian Sea year-round.
Distribution of the Humpback Whale
Humpback whales can be found in oceans worldwide.
Diet of the Humpback Whale
Humpback whales have large plates of baleen, a stiff hair-like substance that is used to strain fish and krill from mouthfuls of water. Baleen is made from keratin, the same substance as your fingernails and hair. Humpback whales use this baleen to filter out and eat small fish, smaller krill, and even smaller plankton.
Humpback Whale and Human Interaction
The humpback whale was threatened heavily during the commercial whaling era, along with many other whale species. According to the National Oceanic and Atmospheric Administration (NOAA), the humpback whale population has increased in many of their distinct populations. The taking of humpback whales was prohibited in commercial whaling in 1966. Today, 4 of the 14 distinct populations are listed as endangered.
Humpback whales today continue to face a number of threats, including:
- commercial fishing gear entanglement
- accidental ship strikes
- habitat destruction
- whale watching ship harassment
- hunting in legal harvests for scientific purposes
- illegal harvest for whale meat
The humpback whale has not been domesticated in any fashion. The immense size of the whale would prevent any practical domestication efforts.
Does the Humpback Whale Make a Good Pet
The humpback whale would not make a good pet, as they are incredibly impractical to keep. Their enormous length makes building an enclosure impractical, and they can eat up to 3,000 lbs. of fish per day.
Humpback Whale Care
Because the humpback whale has never been kept in human care, we do not know much about the potential requirements for caring for them. We do know that they can eat an estimated 3,000 lbs. of fish and krill per day, and travel thousands of miles in yearly migrations.
Behavior of the Humpback Whale
Humpback whales, along with many other cetaceans, will leap out of the water in a behavior called “breaching.” Scientists speculate that humpback whales may breach to remove parasites, to play, or possibly to display dominance. Slapping of flippers and tails on the surface of the water are also thought to be a display of dominance. These acrobatic displays make them a favorite in the whale watching community.
Reproduction of the Humpback Whale
Humpback whales breed at their wintering grounds, in the tropical waters near the equator. Male humpback whales will compete amongst themselves, sometimes battling violently to earn mating rights. Females have a gestation period of 11 months, and give birth to a 2,000 lb. calf. The calf will remain with its mother for 6-10 months.
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Richard W. Merritt, . Joe B. Keiper, in Encyclopedia of Insects (Second Edition) , 2009
This family, also known as humpbacked flies and scuttle flies (4000 species), is another group that exploits a wide range of habitats and exhibits diverse feeding habits. The humpbacked appearance and reduced venation make the adults easy to identify. Many species are consumers of decaying organic matter and can infest household garbage cans; the females are strongly attracted to the odor of decay. Other species are more unusual, specializing on the consumption of slug eggs (some Megaselia) or parasitic on spiders, millipedes, and at least nine insect orders (e.g., Apocephalus, Melaloncha). Some species are currently targeted as potential biocontrol agents of fire ants, a serious pest in the southern United States. One species is known as the coffin fly (Conicera tibialis) because it was reported to maintain many generations on a single human body in the confines of a buried casket.
Production of Dipteran Parasitoids
Maria Luisa Dindo, Simon Grenier, in Mass Production of Beneficial Organisms , 2014
Dipteran parasitoids (especially Tachinidae, but also Sarcophagidae, Phoridae , Cryptochaetidae, and Bombyliidae) comprise a numberd of species of interest for applied biological control and, as a consequence, mass production. Although they are underestimated and often forgotten in biocontrol strategies, several studies concerning their rearing technology have been carried out. The purpose of this chapter is to review the work done on dipteran parasitoids and bring this group of insects to light. Some examples of tachinid and other dipteran parasitoids implicated in biological control are presented in the first section. Subsequently, the most important aspects of their biology relevant for rearing are described. In vivo and in vitro rearing techniques are considered in another section from different points of view, such as host type (natural vs alternative) and age, infestation mode, abiotic conditions, parasitoid nutritional needs, and continuous in vitro culture. Adult maintenance, quality control, and storage and shipment procedures are also discussed. Finally, some perspectives are presented with the aim of stimulating new ideas for research efforts on the mass culturing of dipteran parasitoids.
Oral Nematodes (Panagrolaimidae)
Fatal infection of the external mouthparts and oral cavity and pharynx with entomopathogenic Rhabditida nematodes
Species, Age, Sex
Tarantulas (Theraphosidae), spiders
Genetics and Breed Predisposition
Reported in numerous species from Americas, Africa, and Asia
Reported in terrestrial and arboreal species
Most common after introduction of new tarantulas from other collections
Contagion and Zoonosis
Transmission is so far unclear.
Infection has been known to spread between isolated enclosures in collections.
It has been postulated that Phoridae fungus gnats may act as mechanical vectors spreading the infection between individual spiders in separate enclosures.
Recent work suggests that mealworm beetles (Tenebrior mollitor) contaminating cricket cultures could bring the parasite into tarantula collections.
Unclear whether this is a zoonotic disease
Closely related nematodes have been reported in difficult to treat deep or anaerobic wounds of humans and mammals.
Caution is advised given that a bite from an infected tarantula could potentially result in a human infection.
Geography and Seasonality
Reported in both the United States and Europe
History, Chief Complaint
Physical Exam Findings
Viscous white oral discharge between the fangs and on the chelicerae
Spiders may have a huddled posture or may stand on “tip-toes.”
The nematodes are not usually visible with the naked eye.
Etiology and Pathophysiology
The mode of transmission and details of the life cycle are currently unknown.
It has been postulated that Phoridae flies and mealworm beetles may act as mechanical vectors.
Rhabditida nematode infections are often associated with symbiotic bacterial infections.
These symbiotic bacteria may cause tissue necrosis, aiding the feeding of the nematodes.
Alopecia due to environmental stress in tarantulas (see Alopecia)
Ants (these can kill captive invertebrates in severe cases)
Phoridae humpback flies (very small fruit flies that may also act as a vector for Panagrolaimidae nematode infections; see Panagrolaimidae Oral Nematodes in Tarantulas)
These mechanical methods of mite removal are time consuming. In some cases anesthesia is helpful in performing mite removal with a brush or cotton tip and water based lubricant to trap the mites. Anesthesia will also slow the mites’ movements, making them easier to remove.
There are many insecticides that control fire ants. Baits are advantageous because it is not necessary to find the mounds; ants carry the bait back to their nests. Most fire ant baits consist of corncob grits coated with soybean oil as an attractant. Typically, a toxicant or insect growth regulator is dissolved in the oil. However, none of these solutions are permanent. Efforts are now under way to bring into the United States some of the fire ant parasites and predators from South America. Decapitating flies ( Phoridae ) are one promising predator now being released in Florida and elsewhere. These flies lay their eggs on fire ants. The grub that hatches invades the ant’s head, where it consumes its brain. Ultimately the ant’s head falls off and a new fly emerges. Although these flies parasitize only a small percentage of ants, they do interfere with the ant’s foraging behavior and may make fire ants less competitive with other ants. The flies are spreading from their introduction sites, but their impact on fire ant populations is not yet known. Other potential biocontrol agents include protozoal parasites ( Thelohania solenopsae and even Varimorpha invictae) and parasitic ants from South America (Solenopsis daguerri). A newly discovered fire ant picorna-like virus may kill brood in the colony. Ultimately, a broad approach using chemicals and biological agents will best manage this invasive species.
See Also the Following Articles
Ants ■ Introduced Insects ■ Regulatory Entomology ■ Venom
Enhancement of Biological Control in Annual Agricultural Environments
MARCOS KOGAN, . JOSEPH V. MADDOX, in Handbook of Biological Control , 1999
Assessments of naturally occurring parasitoids are usually based on surveys of individual host species or guilds of hosts. Extensive surveys have been conducted on the parasitoids of some of the major pests of transient crops, e.g., Helicoverpa zea and H. virescens (Fabricius) (Noctuidae) and Nezara viridula (Linnaeus) (Pentatomidae). Helicoverpa zea and H. virescens are highly polyphagous and have been recorded in the United States from 235 plant species in 36 families. A literature survey of the parasitoids of these two species produced 60 species of Hymenoptera in 6 families (Braconidae, Chalcididae, Eulophidae, Ichneumonidae, Scelionidae, and Trichogrammatidae) and 61 species of Diptera in 4 families (Muscidae, Phoridae , Sarcophagidae, and Tachinidae) ( Kogan et al., 1989) . The efficacy of natural control agents in cotton in the United States was assessed by Goodenough et al. (1986) , and King and Coleman (1989) assessed the potential for biological control of Heliothis spp. and Helicoverpa zea and concluded that natural enemies alone would probably remain incapable of controlling the pests throughout their geographic and host ranges.
A partial host record of N. viridula shows that it is also a highly polyphagous species, having been recorded from 44 common cultivated and wild hosts in 18 different plant families ( Todd & Herzog, 1980 ). Jones (1988) surveyed the world literature for records of N. viridula parasitoids and found 57 species in 2 dipteran and 5 hymenopteran families. These lists represent a valuable resource for identifying candidates for biological control.
Species guilds, rather than single species, are often the object of detailed studies. Comprehensive studies of parasitoids of lepidopterous caterpillars in soybean in the United States were reviewed in Pitre (1983) . Ten primary parasitoids and ten hyperparasitoids were recorded on cereal aphids in Europe ( Vorley, 1986 ). In most cases, extensive surveys of common herbivorous insects of transient crops reveal the presence of a rich associated fauna of natural enemies; however, many of those herbivores remain serious pests. Obviously, qualitative surveys reveal very little about the effectiveness of natural enemies in population regulation. Enrichment of the complement of natural enemies of transient crops through augmentative releases or through classical biological control will be discussed in subsequent sections (see also Hokkanen, 1997 ).
Soft Scale Insects their Biology, Natural Enemies and Control
David J. Ponsonby, Michael J.W. Copland, in World Crop Pests , 1997
This subject has been reviewed in depth by Hodek (1973) , Drea & Gordon (1990) and Majerus (1994) . These authors have shown that predaceous coccinellids are themselves attacked by predators, both vertebrate and invertebrate, as well as by a host of parasites, parasitoids and diseases. Vertebrate predators include mammals, birds and lizards, whilst invertebrate predators include spiders and mites, hemipterans, neuropterans, other coleopterous species, dipterans and hymenopterans (Formicidae and Vespidae). Of these, spiders play a key role in depressing coccinellid populations, if not by direct feeding then certainly by trapping them in their webs ( Hodek, 1973 ; Majerus, 1994 ). Parasitic insects are represented by species from two families of Diptera ( Phoridae and Tachinidae) and six families of Hymenoptera (Ichneumonidae, Braconidae, Pteromalidae, Encyrtidae, Eulophidae and Eupelmidae). Of the parasitoids studied so far, only the encyrtids and the eulophids have been found to be important. Up to 95% parasitism of C. bipustulatus was recorded from North Africa by the encyrtid, Homalotylus flaminus Dalman and more than 90% parasitism in Chilocorus species around the Black Sea by a complex of both H. flaminus and the eulophid, Testrastichus coccinellae Kurdjumov ( Hodek, 1973 ). Super- and hyperparasitism are reported from four families (Pteromalidae, Encyrtidae, Eulophidae and Eupelmidae), attacking all stages from egg to pupa.
Other parasites include mites of the family Podapolipidae, particularly those of the genus Coccipolipus which specialise on coccinellids ( Majerus, 1994 ). This study by Majerus (1994) on C. hippodamiae infesting Adalia bipunctata adults showed that the mites (all females) attached themselves to the underside of the elytra and fed on the haemolymph. Eggs were produced and the hatching larvae migrated to the posterior extremities of the elytra, transferring to another host when mating occurred. This parasite is, therefore, sexually transmitted although the effect of its feeding on the host is unknown.
Nematodes have been found to affect only one species of coccidophagous ladybird (an Adalia species feeding on diaspidids in the USSR) despite the fact that several aphidophagous species are known to be affected. Drea and Gordon (1990) attribute this phenomenon to the arboreal habitat of coccid-feeding species and, consequently, their rare contact with the soil.
Pathogens include the two gut-dwelling sporozoan groups, Gregarinida and Microsporidia, and the four fungal genera, Beauveria, Hesperomyces, Fusarium and Laboulbenia ( Hodek, 1973 ; Drea and Gordon, 1990 ; Majerus, 1994 ). The effects of these pathogens on coccinellid populations are not clearly understood although it is thought that a species of Gregarinida (Gregarina katherina), present in 50% of the population of C. bipustulatus and Pharoscymnus anchorago Fairmaire in West Africa, prevented the establishment of Chilocorus stigma Say from North America ( Drea and Gordon, 1990 ). Beauveria bassiana was reported as the most common and virulent fungus on ladybirds but its impact on their mortality is not clear and intensive study is indicated ( Hodek, 1973 ; Drea and Gordon, 1990 ; Majerus, 1994 ).
With the exception of the encyrtid and eulophid parasitoids mentioned above, there appears to be little information relating to the effect of natural enemies on the coccidophagous ladybirds, although there is evidence emerging of some complex ecological relationships between predators of coccinellids (e.g., some spiders – Majerus, 1994 ) and their hosts, and the importance of secondary parasitism and hyperparasitism is little understood in this context. The need for further detailed biological study is indicated.
Physical Transport, Heterogeneity, and Interactions Involving Canopy Anoles
Roman Dial, Joan Roughgarden, in Forest Canopies (Second Edition) , 2004
Dial (1992) reported on the results of suspending small, cylindrical traps (25 cm 2 ) on horizontal lines stretched at mid-canopy height (12 to 15 m) across two gaps (see Figure 15-1 ). The overall mean number of insects captured in small gap traps (1,945 arthropods m −2 12hrs −1 ; n = 23 traps, s.e. = 60.4) was significantly greater than the catch from small within-crown traps (1,241 arthropods m −2 12 hrs −1 ; n = 6 traps, s.e. = 244.4). Using the approach of Dial and Roughgarden (1995) to calculate the expected biomass of gap arthropods as a function of body length using gap arthropod body size distribution and biomass allometry ( Rogers et al. 1976 ) gives a peak biomass for arthropods in the 2 to 3 mm size class ( Dial 1992 ). Many of the same taxonomic orders of insects and spiders captured in crowns (Diptera, Thysanoptera, Hymenoptera, Coleoptera, Homoptera, Araneae, Hemiptera, Psocoptera, Neuroptera, Lepidoptera, Blattodea, Orthoptera) were also captured in gaps (see Figure 15-11 ). The numerical majority of individuals in sticky traps were Diptera in both crowns ( Dial and Roughgarden 1995 ) and gaps (see Figure 15-11 ). Diptera captured in crown and gap traps included many families ( Phoridae , Chironomidae, Sciaridae, Scatopsidae, Psychodidae, Chloropidae, Drosophilidae, Tephritidae, Neriidae) with larval habitats in litter, soil, fungi, and water (Ferrar 1987; Borrer et al. 1989 ), although larvae of Syrphidae and Sarcophagidae were observed in crowns ( Dial 1992 ). Because debris and epiphytes in the canopy had not yet accumulated following Hurricane Hugo, sticky trapped Diptera most likely originated from the ground and other non-arboreal sources.
Figure 15-11 . Taxonomic distribution of arthropods captured using cylindrical sticky traps suspended 11-15 m over two forest gaps shown in Figure 1 . DP = Diptera, TH = Thysanoptera, HY = Hymenoptera, CO = Coleoptera, HO = Homoptera, AR = Araneae, PS = Psocoptera, HE = Hemiptera, LE = Lepidoptera, OR = Orthoptera, NE = Neuroptera, BL = Blattodia. (From Dial and Roughgarden, unpublished manuscript.)
The greater abundance of aerial arthropods over gaps than within forest canopy may be due to several factors. Two possibilities suggested by the literature are: (1) greater food resources for dipteran larvae (including detrital as well as living material) from gap plants than from later suc-cessional plants ( Janzen 1973 ; Coley et al. 1985 ; La Caro and Rudd 1985 ) and (2) insects are attracted to increased light levels within gaps ( Craig and Bernard 1990 ). Dial (1992) reports on the results of a wind vane trap (0.5 m sticky trap-coated rod), where samples showed a significant, positive correlation of insect catch per cm to windward position along the rod (r 2 = 0.81, P = 0.01); during one sample period, the number of insects captured on the first, most windward cm was an order of magnitude more than on the last, most leeward cm of the rod. These results support the conclusion that insects arrive from the instantaneous wind direction. Dial (1992) used two large, fixed-cylinder traps (∼425 cm 2 ) to estimate the circular mean direction of arthropod catch and circular statistics ( Stephens 1962 ; Batschelet 1965 , 1981) and found that the mean direction differed significantly from random (V-test, P = 0.005). Arthropod catches on the large, fixed cylinders indicated a general southeasterly origin of arthropods during those months (see Figure 15-12 ).
Figure 15-12 . Compass rose distributions for number of arthropods captured 11-15 m over two gaps shown in Figure 15-1 using large, fixed cylinder sticky traps. (From Dial and Roughgarden, unpublished manuscript.)
In summary, five lines of evidence suggest that wind transports aerial arthropods into forest canopy from adjacent gaps. First, sticky traps caught more arthropods within windward crowns than in leeward crowns. Second, arthropods existed in the air within crowns and over gaps with Diptera predominating in both habitats. Third, significantly more arthropods were captured in gap traps than in crown traps. Fourth, arthropods arrived from the instantaneous wind direction. And fifth, the mean direction of arthropod arrival coincided with an easterly trade-wind direction. It appears that the observed spatial distribution of canopy anoles within the forest canopy at this site may represent the local consumers’ response to variation in non-local resource abundance, variation determined by canopy structure and wind direction. These conclusions follow from: (1) arthropods in observed lizard diets (see Figure 15-7 ), (2) lizard depletion of these arthropods ( Section III ), and (3) evidence from gap catches of arthropods.
3 Characteristics of Insect Parasitoids
Insect parasitoids are smaller than their host and are specialized in choice of host. Only the female searches for hosts and usually destroy their hosts during development. Different parasitoid species attack at different life stages of the host. Eggs are usually laid in, on, or near the host. The immature stages remain on or in the host and almost always kill the host ( Hoffmann and Frodsham, 1993 ). Adult parasitoids are free-living, mobile, and may be predaceous. With respect to population dynamics, parasitoids are similar to predatory insects.
Parasitoids attack either by penetrating the body wall and laying eggs inside the host or attaching eggs to the outer body surface. The immature parasitoid develops on or within the host, consumes all or most of the host’s body fluid, and pupates either within or external to the host ( Hoy, 1994 ). The adult parasitoids emerge from pupae and start the next generation afresh by actively searching for a host to oviposit. The life cycle of the pest and the parasitoid can coincide, or that of the pest may be altered by the parasitoid to accommodate its development. Most adult parasitoids require food such as nectar, pollen, or honey dew and many feed on host’s body fluids, whereas others require free water as adults ( DeBach and Rosen, 1991; Altieri and Nicholls, 1998 ). Parasitism is found in at least five insect orders, i.e., Hymenoptera, Diptera, Coleoptera, Lepidoptera, and Neuroptera ( Eggleton, 1992 ), but the most parasitoids that have been used in biocontrol are from the insect orders Hymenoptera and, to a lesser degree, Diptera ( Van Driesche and Bellows, 1996b ). Hymenopteran parasitoids account for nearly 78% of the estimated number of species and consequently have served as models of choice for nearly all research on insect parasitoids ( Godfray, 1994; Hawkins and Sheehan, 1994; Waage and Greathead, 1986 ). The superfamilies Ichneumonoidea and Chalcidoidea are among the largest assemblages within parasitoids. Members of these superfamilies are parasitoids of economic importance and have been used in many biocontrol programs ( LaSalle, 1993 ). There are several unique factors that are responsible for the success of hymenopterans as parasitoids, they are the only holometabolous parasitoids retaining a primitive lepismatid form of ovipositor and associated accessory glands. This modified ovipositor is used to gain direct access to concealed host, secrete venom to paralyze the prey, lay eggs, secrete feeding tubes, and locate prey via sensitive neural receptors. Only hymenopteran parasitoids are haplodiploids. Such a sex-determining system gives females control over the sex ratio of the progeny ( Charnov, 1982 ). The most frequently used groups in the order Hymenoptera are Braconidae and Ichneumonidae in the superfamily Ichneumonoidea, and the Eulophidae, Pteromalidae, Encyrtidae, and Aphelinidae in the superfamily Chalcidoidea. About 66% of all successful biocontrol programs have involved parasitoids that belong to the order Hymenoptera.
Dipterans include an estimated 16,000 described species of parasitoids, about 20% of the known species with this lifestyle ( Eggleton, 1992 ). Within Diptera, several families are parasitic but are less amenable in biocontrol programs. These families include Sciomyzidae, Bombyliidae ( Yeates, 1994 ), Calliphoridae ( Rognes, 1991 ), Phoridae ( Disney, 1994 ), Sarchophagidae ( Pape, 1987 ), Rhinophoridae ( Pape, 1986 ), and Tachinidae ( Belshaw, 1993; Hertig, 1960; Mellini, 1990; Pape, 1992 ). The family Tachinidae is the most frequently employed group as parasitoids ( Greathead, 1986 ). The dipteran parasitoids in Tachinidae appear to be less host-specific. Some species of tachinid flies have been found to attack more than 100 different host insects. The family Tachinidae, which is exclusively parasitic, has many species that have been manipulated for biocontrol for a range of pest taxa. Examples of dipterans as parasitoids include the parasitoid, Lydella thompsoni, that was used against European corn borer, Ostrinia nubilalis; Lixophaga diatreae used in the Caribbean against the sugar cane borer, Diatraea saccharalis; and Cyzenis albicans introduced to Canada against the winter moth Operophtera brumata ( Arnaud, 1978; McAlpine, 1981 ). Although parasitoids have also been recorded in the insect orders Strepsiptera and Coleoptera, parasitism is not common in them ( Greathead, 1986 ). Table 1 depicts the common parasitoids found in agroecosystem.
Table 1 . Common Parasitoids Found in Agroecosystems
|Diptera||Tachinidae||Beetles, butterflies, and moths||Internal|
|Phoridae||Ant, caterpillar, termites, flies, others||Internal|
|Hymenoptera||Chalcididae||Flies and butterflies (larvae and pupae)||Internal or external|
|Encyrtidae||Various insect eggs, larvae, or pupa||Internal or external|
|Eulophidae||Various insect eggs, larvae, or pupa||Internal or external|
|Aphelinidae||Whiteflies, scales, mealybugs, aphids||Internal or external|
|Myrmaridae||True bugs, flies, beetles, leafhopper eggs||Internal|
|Scelionidae||Insect eggs of true bugs and moths||Internal|
|Ichneumonidae||Larvae or pupae of beetles, caterpillars, and wasps||Internal or external|
|Braconidae||Larvae of beetles, caterpillars, flies, and saw flies||Internal (mostly)|
|Pteromalidae||Larvae and pupae of lepidopteran and Coleopteran insects||Internal|
Modified from Hagler (2000) .
3.1 Classification of Parasitoids
A wide group of parasitoids lay eggs on or inside the body of insect hosts, which are then used as food by the developing larvae. The most important parasitoid groups that parasitize the eggs of the host insects are trichogrammatids, ichneumonids, scleonids, evanids, chalcids, and tachinids ( Quicke, 1997 ). The trichogrammatids parasitize the eggs of several insect species and have been used extensively in biocontrol programs ( Flint and Dreistadt, 1998 ). The braconids, bethylids, and ichneumonids parasitize mainly the larvae of moths and butterflies ( Hrcek et al., 2013 ). The chalcids, braconids, and encyrtids parasitize the eggs and larvae of insects. Certain ichneumonids, eulopids, and chalcids parasitize both larval and pupal stages of insects. An epricania, Epiricania melanoleuca (Fletcher), parasitizes Pyrilla perpusilla (Walker) on sugar cane, and is an adult parasitoid belonging to the order Lepidoptera ( Kumarasinghe and Wratten, 1996 ).
Parasitoids may be classified depending upon whether they are external feeders (ectoparsitoids) or internal parasitoids (endoparasitoids) ( Doutt et al., 1976 ). Ectoparasitic species are generally found in situations where the host is protected, i.e., leaf miners or scale insects. In these circumstances, the adult parasitoid may simply deposit an egg inside a feeding tunnel (leaf miner) or near the host without making a direct contact with the host. Endoparasitism is more common in hosts that are not protected, such as aphids or caterpillars, where the adult parasitoids directly deposit the egg inside the host with their ovipositors ( Doutt et al., 1976 ).
Parasitoids may have only one generation (univoltine) or two or more generations (multivoltine) ( Van Driesche and Bellows, 1996b ). Life cycles are generally short, ranging from 10 days to 4 weeks or so in summer but correspondingly longer in cold weather. However, some require a year or more if they have hosts having only a single generation per year. In general, they all have great potential rates of increase.
Parasitoids may be either solitary, when only one larva develops per individual host, or gregarious, when more than one larva develops upon a single host. However, this is not always clear cut, as many species may develop facultatively as solitary upon a small host and gregarious upon a larger one ( DeBach and Rosen, 1991 ). Adult parasitoids seek out their hosts using a variety of cues such as visual, olfactory, and tactile, from the target host and its habitat. Parasitoids may be either idiobiont, i.e., the host’s development is arrested or terminated upon parasitization (e.g., egg parasitoids) or koinobionts, i.e., the host continues to develop following parasitization (e.g., larval–pupal parasitoids) ( Doutt et al., 1976 ).
Some species of parasitoids are polyembryonic, where a single egg gives rise to many embryos. Other parasitoids display superparasitism, where more than one adult of the same species attacks the host, and multiparasitism, where more than one species attacks the same host. Both super and multiparasitism are generally regarded as undesirable situations because much reproductive capacity is wasted.
When one parasitoid is attacked by another parasitoid the phenomenon is called hyperparasitism. Hyperparasitoids are secondary insect parasitoids that develop at the expense of primary parasitoids, thereby representing a highly-evolved fourth trophic level. They are called secondary parasitoids if they attack primary parasitoids and tertiary parasitoids if they attack secondary parasitoids. Secondary parasitism is usually harmful, as it reduces the efficacy of primary parasitoids ( Sullivan and Volkl, 1999 ).