Such structures often cause considerable damage to man, e. Beneficial Arthropods: Arthropods which are beneficial have great commercial value.
The crustaceans like prawn, lobster, crab and shrimps are regarded as delicious foods. A large number of Crustaceans which live as plankton serve as the food of fishes which in turn are the foods of man. Numerous birds and also several mammals are insect eaters.
Man gets honey from honey-bee, silk from silk worm and lac from lac insects. Numerous Insects, Arachnids, Diplopods are insect-eaters and they serve us by destroying many injurious Insects and Arachnids. From our knowledge of arthropods we have learnt the handling of injurious and beneficial insects. It has been realised that instead of indiscriminate use of insecticides it is necessary to rely more on biological controls.
A number of problems are still unsolved and require further investigation. They are social insects and live in large colonies, each colony having a single queen.
Their body is soft which easily gets desiccated and, hence, they live in earthern galleries or mounds. Their mouthparts are of the biting type and they have two pairs of similar elongated wings placed in sockets which are easily shed after the first flight.
Caste system among them is highly developed. The most common forms are workers and soldiers which are both sterile females and males. The sexual forms may be winged macropterous or short-winged brachypterous or may be wingless apterous. The whiteants Termitidae may be subterranean Coptotermes , may live in dry wood Mastotermes , may form mounds Odontotermes , or they may make huge termitaria Nasutitermes.
The queen is the life of the colony and if she dies the colony may perish. Practically, all termites feed on the cellulose obtained from dead plants, wood, wooden structures, books, etc.
They also attack crops, particularly sugarcane and wheat sown under unirrigated conditions. Their mouthparts are of the biting type and they have no cerci. About 1, species are known. They are ectoparasites of birds and a few of them are also found on mammals. The thoracic segments are more or less free and the tarsi may be 1-or 2-segmented. They attach eggs to the feathers of their hosts and complete life-cycle without dropping off. Separated from the host, the lice cannot live for long.
They are wingless insects having piercing- and-sucking type of mouthparts, with which they suck the blood of their host. Their thoracic segments are fused and they have 1-segmented tarsi, and a single claw with the help of which they cling to the hair of their host.
The body louse of man, Pediculus humanus Linnaeus Pediculidae and the cattle louse, Haematopinus Haematopinidae are the common examples of this order. Many of the forms are apterous and in some, there may be an incipient pupal instar. There are two suborders, Heteroptera and Homoptera.
In the former, the basal half of the fore wing is of a much harder consistency than the rest of it. The plant bugs are medium insects and the important crop pests include the rice bug, Leptocorisa acuta Thunberg Coreidae , the green potato bug, Nezara viridula Linnaeus Pentatomidae , the red cotton bug, Dysdercus koenigii Fabricius Pyrrhocoridae , the lace bug, Urentius sentis Distant Tingidae , the dusky cotton bug, Oxycarenus laetus Kirby Lygaeidae.
The common bed bug, Cimex lectularius Linnaeus Cimicidae although wingless, also belongs to this suborder. In the second suborder, Homoptera, the fore wings, when present, are of a uniform consistency and it includes such crop pests as leafhoppers Cicadellidae , aphids Aphididae , pyrilla Fulgoridae , citrus psylla Psyllidae , the whiteflies Aleyrodidae and the scales Diaspididae.
Such commonly known insects as cicadas Cicadidae and the lac insect Lacciferidae also belong to this suborder which is of great importance in agriculture. This order is known to contain 59, species. They are minute insects with segmented antennae.
The mouthparts are stylet-like and are used for rasping and sucking plant sap. The tarsi are short-each ending in a vesicle. In the life-history of these insects, there is an incipient pupal instar. The thripses are commonly seen in flowers, but they may also feed on leaves. The well-known pest species are the grapevine thrips, Rhipiphorothrips cruentatus Hood Heliothripidae and onion thrips, Thrips tabaci Lindeman Thripidae.
They are small to large insects with soft bodies, and their larvae are campodeiform with biting or suctorial mouthparts, and are generally predacious. The larvae of lace wings destroy a large number of aphids, and those of the ant lions dig typical funnel-shaped pits in the sand and wait for stray ants to fall in and serve as their prey.
They are small to very large insects in which the galeae are modified to form a spirally coiled sectorial proboscis used for sucking nectar from flowers and in some cases the fruit juice. Their larvae are active, mostly phytophagous, and some also feed on wax and cloth. Their pupae are object or partially free and are usually enclosed in cocoons.
It is very large order of 1,19, species and many of them are brilliantly coloured. The lepidopteran larva has a well-developed head, 3 thoracic and 10 abdominal segments. Abdominal feet or prolegs are present on segments and In some, the numbers of pairs are reduced and consequently, as they walk they form a loop of the body and are known as semiloopers or loopers. Distinguishing Characteristics of Moths and Butterflies: Moths: i.
Eggs — Generally flat and round ii. Larvae — Generally covered with hairs iii. Ocelli — Two ocelli present iv. Type of antennae — Thread-like, comb like or feathery v. Pupation — Pupae are mostly enclosed in silken cocoons vi. Shape of body — Relatively large body vii. Pattern of resting position of the wings — The wings lie in a slanting roof-like disposition on either side of the body-length viii.
Activity time — Usually night-fliers Butterflies: i. Eggs — Cigar shaped and cylindrical ii. Larvae — Smooth and naked iii. Ocelli — Absent iv. Type of antennae — Club-shaped v. Pupation — Pupae are naked vi. Shape of body — Slender body vii. Pattern of resting position of the wings — The wings are held over the back in the vertical position viii.
Activity time — Day-fliers As pests of crops, this is the most important order and in a tropical country, such as India, several hundred species are known pests of economic plants.
Out of these, over 50 are major pests. Some of the commonest pests are the cutworms, Agrotis spp. The silk moth, Bombyx mori Linnaeus Bombycidae , has a great economic importance as a producer of commercial silk.
Their mouthparts are modified into a proboscis used for piercing and sucking or sponging liquid foods. The typical larva is worm-like, legless, and has an indistinct head. It has a terrestrial, aquatic or parasitic mode of life, the pupa is weakly object or exarate, enclosed in a puparium made of the last larval skin. There are three suborders- Nematocera, in which the larva has a well-developed head; Brachycera, in which the head is incomplete and retractile; and Cyclorrhapha, in which the head is vestigial.
The mosquito Culicidae belongs to the first suborder; horse flies Tabanidae and robber flies Asilidae belong to the second; the hover flies Syrphidae , leafminers Agromyzidae , blow flies Calliphoridae and the house fly Muscidae belong to the third suborder. This is a very large and important order comprising about 1,19, species. The adults are ectoparasites with the body laterally compressed.
The rat flea, Xenopsylla cheopis Rothschild Pulicidae frequently migrates to man and transmits the bacillus of bubonic plague. Their mouthparts are of the biting type and sometimes of the lapping or sucking type. The first segment of the abdomen is fused with thorax, often like a narrow petiole. The pupae are generally enclosed in cocoons. Hymenoptera is divided into two suborders.
Females live longer than males on average: 60 and 48 days, respectively. The well-known pests of paddy are Spodoptera mauritia, Heliothis armigera, Agrotis ypsilon, Cirphis albistigma, Psalis securis, Nymphula depunctalis, Melanitis ismene, Schoenobius incertulus all belonging to the Lepidoptera , Hispa armigera Coleoptera , Leptocorisa acuta, Ripersia oryzae both Hemiptera and a few others from Diptera, Thysanoptera and Orthoptera. It is important to restate the thesis and three supporting ideas in an original and powerful way as this is the last chance the writer has to convince the reader of the validity of the information presented. Austin GD, Analysis: A gay movement s dissertation essay shows your understanding of how the author builds an argument by: Examining the authors use of evidence, reasoning, and other stylistic and persuasive techniques Supporting and gay movement s dissertation claims with wellchosen evidence from the passage Writing: A successful essay is focused, organized, and precise, with an appropriate style and tone that varies sentence structure and follows the conventions of standard written English.
Host Plants Back to Top Leptocorisa acuta feeds primarily on graminaceous plants such as rice, wheat, and sugarcane Hill
Heteroptera of Economic Importance. Nymphs: A week following oviposition, the eggs hatch, and within hours the nymphs begin feeding Corbett International Rice Research Newsletter, 6 1 When they are freshly deposited, eggs are a cream-yellow color, turning to a reddish-brown after approximately one week. Malathion and Methylparathion dust is also effective.
The lepidopteran larva has a well-developed head, 3 thoracic and 10 abdominal segments. Alternate host plants and hibernation of the rice bug Leptocorisa acuta in North Bengal. Activity time — Usually night-fliers Butterflies: i. About 1,95, species of this order have been described so far. The auditory organs are located on the first abdominal segment. Tropical Pest Management
Excessive feeding can cause yellow spots on the leaves. Populations tend to increase during the flowering stage of the rice crop, which coincides with warmer weather. A large number of Crustaceans which live as plankton serve as the food of fishes which in turn are the foods of man. Symphyta includes the wood-boring wasps.
The sexual forms may be winged macropterous or short-winged brachypterous or may be wingless apterous. Their mouthparts are of the biting type and they have two pairs of similar elongated wings placed in sockets which are easily shed after the first flight. The food should be both good tasting and good for you. They are social insects and live in large colonies, each colony having a single queen. A large number of pests are also known in wheat Sesamia inferens, Agrotis ypsilon, Toxoptera graminum , in Sugarcane several members of the group Lepidoptera, e. These bugs have globular, protruding eyes in addition to small ocelli simple eyes , which are difficult to see.