Volume 96, Issue 5
September 1987, pages 437-646
pp 437-438 September 1987
pp 439-450 September 1987
Drosophila is a suitable system to study different facets of population differentiation.Drosophila sulfurigaster, Drosophila bilimbata, Drosophila albostrigata, Drosophila neonasuta andDrosophila pulaua are morphologically indistinguishable members of the orbital sheen complex of thenasuta subgroup ofDrosophila. They are distributed in different parts of south east Asia. The evolutionary inter-relationship between these closely related forms will be discussed with reference to karyotypes, heterochromatin, satellite DNA, population fitness, ecogenetic divergence and isozyme variations.
pp 451-459 September 1987
Drosophila nasuta nasuta (2n=8) andDrosophila nasuta albomicana (2n=6), a pair of cross fertile races have conspicuous karyotypic divergence and symptoms of postmating isolating mechanisms. Hybridization of these races followed by hybrid maintenance and hybrid recombination has resulted in the evolution of two novel races with new combinations of parental chromosomes referred to as Cytoraces I and II and this has illustrated an interesting aspect of karyotypic differentiation under laboratory conditions.
pp 461-467 September 1987
Cytological parameters are nowadays being increasingly and intelligently used in solving the taxonomic problems of dubious species. Aphids’, in certain cases atleast, taxonomy is not stabilised at the species as well as at the subgeneric level. It is because of the usual occurrence of race or biotype in natural population. Occurrence of such taxonomic categories are possibly due to chromosomal rearrangements or otherwise that resulted from the association with a host plant, as evidenced in a few species, viz,Myzus persicae, Brachycaudus helichrysi, Tuberolachnus salignus etc. Several ecogeophysical factors are operative in establishing chromosomally distinguished races which demand the attention of taxonomists for further taxonomic evaluation of the concerned species. Attempt is therefore made to discuss the rationale of using the cytological informations in the identification of infraspecific categories of aphids.
pp 469-477 September 1987
Among the egg parasites used extensively for biological control of various lepidopterous pests all over the world the species ofTrichogramma andTrichogrammatoidea (Hymenoptera, Trichogrammatidae) are the most important. The mode of reproduction of most of these is arrhenotoky while a few inTrichogramma is thelytoky, the later could be facultative with change in temperature, from one mode to the other. Since 1977, a large number of new species were described and studies on different aspects made world over. The studies made include crossing experiments which proved existence in nature of sibling species and other categories of incipient speciation which otherwise are difficult to discern. Studies on isozyme and enzyme analyses showed important differences among species and populations ofTrichogramma, so also response by these to different chemical insecticides. Scanning electron microscopy is yet another important tool to supplement other differentiating factors. Other biological characters aiding systematics include sex ratio, life and fertility table studies showing breeding potential, host preferences, temperature tolerance, etc.
pp 479-483 September 1987
Species of the genusAphytis Howard (Hymenoptera, Chalcidoidea, Aphelinidae) develop as primary ectoparasites of armoured scale insects (Homoptera, Coccoidea and Diaspididae) and are the most important natural enemies of this group of pests. Several species have been successfully employed in the biological control of important armoured scale insect pests in different parts of the world. In spite of the importance ofAphytis, very little is known about the species occurring in India, a promising area for additional and important species. In the past although taxonomists have made significant contributions to our knowledge of Indian Chalcidoidea, the genusAphytis has largely been neglected because the identification of the species in this group is extremely difficult for want of readily recognizable morphological criteria and due to the common occurrence of sibling and uniparental species. The recognition of sibling species and different biological races is often important in biological control. Hence there is a need in India to initiate studies onAphytis to establish the identity of cryptic species and to recognize biological races and other infra-specific entities exhibiting morphological and biological differences, with special attention to those parasitic on armoured scale insects on economically important plants. These studies would pave the way for biological control strategies for pest species in India and elsewhere and also for those which may eventually attain pest status due to changing ecosystems.
pp 485-497 September 1987
The feeding behaviour exhibited by the different subfamilies of Reduviidae is distinctly correlated with the specific prey types involved. Important adaptive modifications are seen associated with their methods of prey capture and feeding. Based on the analyses of feeding behaviour, reduviids may be grouped as (i) ‘blood feeding’ type, (ii) ‘sticky-trap’ type, (iii) ‘raptorial’ type, (iv) ‘wait and grab’ type, (v) ‘pin and jab’ type and (vi) ‘chase and pounce’ type. The oviposition methods are highly varied in Reduviidae and it is possible to assign group characteristics, but the ultrastructure of the eggs, particularly those of chorionic collar extensions and the operculum, indicate subfamily resemblance. The usefulness of feeding and reproductive behaviours and the egg ultrastructure in the biosystematics of Reduviidae are discussed.
pp 499-508 September 1987
Biosystematic studies of 3 subfamilies of Reduviidae viz Acanthaspidinae, Harpactorinae and Piratinae have provided sufficient data for clear demarcations of these subfamilies in terms of biological, behavioural and morphological tools. Biological considerations involve incubation and stadial periods, hatchability, adult longevity, sex ratio and morphometric analyses of life stages. Behavioural parameters include nature of predators, camouflaging, death feigning, head nodding, spitting, nymphal rolling, mating and oviposition of the members of these 3 subfamilies. Information on the bioecology of 25 species, behavioural aspects of 40 species and morphological aspect of 165 species serve to adequately augment our understanding of the biosystematics of this important predatory group of insects.
pp 509-515 September 1987
Bruchidae forms a small compact group of phytophagous Coleoptera with well defined ecological limits. Its members are by and large seed eaters, mostly attacking the seeds of Leguminosae including edible legumes. Several genera show definite host plant relationships and many species present strict host specificity. The bruchids of economic importance fall into two categories viz (i) store bruchids and (ii) field bruchids, with separate voltinism and distinct pattern of development. The bruchids of no recognized economic importance also have characteristic host plant relationship, pattern of distribution and avoidance of interspecific competition. Apart from the known taxonomic discrimination on the basis of external morphology, the genera and species can also be characterized from variations in the internal anatomy, the number and structure of chromosomes and the quality and quantity of their macromolecules. Behavioural peculiarities are also useful for the discrimination of species and genera. The time, manner and duration of copulation, site of oviposition and time and methods of emergence provide useful variations. Compatibility and incompatibility of various host seeds dependent on the amount of non protein aminoacids, antiprotease compounds, hemagglutinin fractions and other toxic substances for different bruchid species and the capability of the latter for combating the same also provide valuable demarcative information.
pp 517-525 September 1987
Membracids, in general, display a very few morphological characters of taxonomic value. Many species exhibit remarkable intraspecific variations, in addition to sexual dimorphism and cornuate polymorphism that makes it difficult to allocate them to their respective taxa, unless a long series of male and female individuals belonging to the same population are available for examination. The male genitalia, although of value in the diagnosis of higher categories of the Membracidae, find limited application at the species level. The nymphal characters, especially those of the fifth immature stage, are very useful in the identification of the species, but nymphal materials are not available except for a few species, and the host plants of many species remain unknown. In recent years, it has become imperative to consider the ecophysiological aspects of these insects for a better and precise understanding of their systematics. The host plant specificity of some species of membracids, the mutual association of a particular species of membracids with a particular species of ants and the parasite-host interaction involving certain chalcidoid egg parasites of membracids are considered with a view to evaluate their role in the membracid taxonomy. The impact of differential reproductive potential in terms of host diversity, the allochronic differences in mating and initiation of oviposition, and the differences in the relative growth patterns with particular reference to the polymorphic speciesOxyrhachis tarandus (Fabricius) on 5 species is investigated.
pp 527-532 September 1987
The grouse locusts (Tetrigidae) represent a group of small sized Caeliferan Orthoptera. These are considered to be primitive orthopterans related to Tridactylids on one hand to Acridids on the other. This family is represented in Indian subcontinent by about 90 species belonging to 35 genera. In the present study haemolymph protein profiles from 7 species from this family have been studied as an additional parameter to understand interrelationship amongst them. It is noted that the speciesParatettix dorsifer andEuparatettix personatus belonging to the same subfamily Tetriginae show remarkable similarity in the haemolymph protein profile, thus justifying their classical taxonomical grouping. In case of subfamily Scelimeninae, however, of the 4 species studied 3 species vizEucriotettix flavopictus, Criotettix latifrons andThoradonta pruthii show a marked similarity, howeverEucriotettix harpago shows a pattern closer to that observed in the subfamily Cladonotinae. This implies that though by classical taxonomic criteria the 4 species are close to each other this may not be a very natural grouping.
From this observation it becomes clear that help from additional parameters like protein profile studies, immunochemical studies, cytogenetic analysis, etc will prove to be very valuable for the real understanding of phylogenetic interrelations and evolution of this family in particular and the status of grouse locusts vis-a-vis the orthopteran insects in general.
pp 533-542 September 1987
The fig wasps form a heterogenous group of microhymenopterans showing convergent evolution in response to adaptations for life in their unique habitat—the interior of the syconia of the differentFicus species. Sexual dimorphism is very common among the various tribes of the chalcidoid families constituting the fig wasps. This is in response to the different types of functions that the female and the male sexes are called upon to perform in their specialized habitat. The unisexual variations commonly met with in the male sex and rarely in the female sex, in the cleptoparasitic tribes belonging to theTorymidae and thePteromalidae may be attributed to competitive feeding on a limited provision of food—a trophic factor. In the homeomorphic sexes of the subfamilyEpichrysomallinae (Pteromalidae) copulation takes place outside on the top of the syconia. The importance of making observations on the biology including mating behaviour of the dimorphic (apterous and alate) males in the subfamilySycophaginae (Torymidae) for the proper study of the systematics of this group is stressed.
The true fig wasps which are the fig pollinators (Agaonidae) are generally highly host specific, i.e. only one species of these pollinators is associated with a given species ofFicus. TheFicus species and its wasp pollinator are in intimate symbiotic relationship. There has been co-evolution of theFicus species with its specific wasp pollinator. The females of these pollinator wasps often possess pollen storing structures as well as the behavioural attributes for the active collection of pollen from the stamens of the ripe fig and for the active dispersal of pollen on to the stigmas of the ovaries of flowers of tender figs into which these females penetrate for oviposition.
The ecological niche of theFicus syconia is virtually identical to that of many plant galls and as such attract many species of gall-inhabitingEurytominae (FamilyEurytomidae). SuchEurytominae include a variety of genera, with numerous species both of phytophagous and entomophagous habits.
The modern systematics of the fig wasps is based on the above aspects of their functional morphology, biology, convergent evolution, sex-limited variations, sex-limited dimorphism, host specificity, behavioural attributes, etc. A conspectus of the modern classification of the figChalcidoidea is presented.
pp 543-550 September 1987
The Chalcididae represent a large group of parasitic Hymenoptera which parasitise pupal or larval stages of various insects including several pests. Their phylogeny is not so far clearly known, but a Eurytomid—Torymid line of accent could be postulated. There is a general resemblance in their adult behaviour such as emergence, courtship, mating, oviposition, feeding etc. Their hosts belong to Lepidoptera, Diptera, Hymenoptera, Neuroptera, Coleoptera and Strepsiptera.
pp 551-559 September 1987
The Brown planthopper,Nilaparvata lugens (Stal) is causing serious damage to rice cultivation in tropical countries of Asia for the last 10–15 years. Green leafhoppers,Nephotettix spp. are also assuming serious proportions in different parts. This has been attributed to improved rice production technology, especially with the introduction of high yielding varieties. Damage is not only through loss of sap as a result of feeding but also by transmitting diseases in this process. Various reasons have been attributed like breaking of resistance, migration, insecticidal treatment etc. One such reason, which led to the biosystematic studies of these pests is the assumption that this is due to evolution of new forms referred to as biotypes. Of late biotypes have also been reported inNephotettix virescens. This term is basically used with reference to differential ability of the insect to infest particular rice cultivars having resistant genes. This phenomena is attributed by some scientists, not to the breaking of resistance, but to the evolution of new forms which are different from the original population. As per the conventional taxonomy, this new form is similar to the original form, and hence biosystematists attempted various methods like chemical and honeydew analyses, cytology, acoustic behaviour, morphometrics, etc in order to help the breeders in differentiating and identifying these and also to find out the mechanism and causes evolving such biotypes.
pp 561-572 September 1987
Garhwal and Kumaun ranges of Himalaya include 250 odd species of aphids infesting a number of agricultural and forest plants. Out of these only 52 species (20%) are found to be gall formers. Majority of these gall aphids (63%) are indigenous. Except 4 species which produce true galls on stems, all other species are known to produce leaf fold or leaf roll or leaf base galls.
In general, the gall forming aphid species are heteroecious i.e. alternate between their primary and secondary hosts in different periods of the year. However, a few have been found to be autoecious i.e. monophagous. These aphids are also highly polymorphic in nature. Unless morphs from both of their primary and secondary hosts are available their identities in some cases are difficult. It has been observed that the morphology of aphid galls, karyomorphology, host association, life cycle pattern and natural enemies (both predators and parasites) help in the identity of such aphids more precisely, particularly in the closely related species complexes.
pp 573-581 September 1987
Pure systematics of Agromyzids attracted the attention of many entomologists quite early in the century, but investigations on their biosystematics is still to gain the necessary attention and recognition from entomologists. Their life history and feeding habits being so closely interelated with the chemical nature of their host plant, investigations into their capability to select the right host plant become all the more important. It has become very essential to critically reassess their systematic position and the characters governing this sensitive interspecific relationship. Factors which require special attention in this regard are: (i) the organs and devices responsible for host recognition and host selection, (ii) correlation between the structure of these organs and the behaviour of these flies, (iii) recognition of special features in their biology and (iv) the study on the interrelationship between ecological factors and the special features in their biology.
Though agromyzid infestation causes damage to varied plant parts such as root, stem, leaf and seed etc there is striking structural similarity in the organs and devices responsible for host selection. This is mainly due to the fact that in all cases it is the adult fly which is responsible for choosing the host. As very little information is available on the correlations between structural adaptations for host recognition, selection and the behaviour of Agromyzids, an attempt has been made to highlight these aspects.
pp 583-586 September 1987
The sarcity of positively associated stages of adults of both sexes and the remarkably little variation shown by the adults of a very few species studied have naturally led to the recognition of the so-called pupal cases, the exuviae of the IV instar nymphs in the matter of generic and specific classification of the aleyrodids—a rather unusual procedure in the taxonomic study of these insects. This stage is the one most often collected and known in the species world over and also possesses a multitude of diagnostic features than in any other stage.
pp 587-611 September 1987
The biology and micromorphology of the eggs of 40 species belonging to 26 genera and two subfamilies of Tingidae from southern India have been studied and considered for an assessment of their biosystematics. The oviposition strategy is intimately correlated with the selection of oviposition site on the host plant, determined by the shape and size of the egg and accomplished by appropriately developed ovipositing mechanism involving the structural features of the first gonapophyses. The oviposition pattern is accordingly classified and the eggs are classified on the basis of the nature of development of the chorionic collar cum opercular apparatus. Characterization of the eggs and assessment of their systematic importance have been linked with the origin and evolution of adaptive radiation of oviposition strategies of their egg parasitoids as well. Production of season oriented dimorphic eggs is common among species that oviposit their long operculate eggs vertically in clusters, either into stems or rachis or pistil. Lamina ovipositors preferentially oviposit into the mesophyll horizontally, without cluster formation, on the undersurface of the leaves and the significant reduction in the number of aeropyles of such oval, short operculate eggs could be correlated with the abundance of oxygen supply of the ambient air. More elongate, long operculate eggs in Tingidae, characterized by their multiplicity of aeropyles and vertical oviposition in clusters into stems, rachis and pistil, signify primitiveness, as observed in Cantacaderinae and some large sized Tinginae. Micropyles are absent in tingid eggs, as fertilization occurs before chorion formation and a true spermatheca is wanting.
pp 613-618 September 1987
Lepidoptera constitutes one of the dominant groups of insects in the forest ecosystem, both in terms of species diversity as well as their economic importance. Segregation of taxa in this order is mainly based on the external morphological characters at supraspecific and specific levels, although the morphological details of genitalic armature are also currently being used. More recent trends in the systematics of this group include studies of their ultrastructure, biochemistry, karyology, biometry, cytogenetics etc.
Lepidopterans differ in their habits and habitats, each species having its characteristic habitat requirements, but very sensitive even to slight changes in the environment. As a result, members of different populations which are subject to extrinsic factors affecting the habitats, host-plants or associated organisms exhibit considerable variation. Besides, changes are also brought about by intrinsic factors like parthenogenesis, intraspecific hybridization, changes in the genetic constitution of individuals, etc, which result in a high degree of intraspecific variability within a population.
pp 619-628 September 1987
In recent years increasing number of studies have been undertaken involving modern techniques like DNA hybridization, analysis of enzymic and chromosomal polymorphism in conspecific populations, ecophysiology and behaviour in individual species etc with far reaching implications in the systematics of Entognathous Apterygota, particularly the Collembola. Both scanning and transmission electron microscopes have been used extensively for the study of surface structure, sense organs, spermatozoa and gut providing considerable insight into phylogenetic relationship of higher taxa as well as interrelationships at the generic and lower taxonomic levels.
pp 629-636 September 1987
Culex vishnui group consists of 3 species of mosquitoes vizCulex vishnui, Culex pseudovishnui andCulex tritaeniorhynchus. It was found that out of 16 species of mosquitoes collected in 3 years from two different biotopes, 8·28 and 24·89% ofCulex vishnui mosquitoes were collected from human habitations and cowsheds respectively. The corresponding data ofCulex pseudovishnui were 1·80 and 5·66% respectively. Out of 12274 mosquitoes belonging to 17 species collected off man-baits in one year,Culex vishnui constituted 34·6% while the latter species encountered 9·04%. When the collection was made by placing manbaits and cow-baits side by side, the attraction ratio (man:cow) ofCulex vishnui was found to be 1∶1·9 and that ofCulex pseudovishnui was 1∶2·6. Bloodmeal analysis of these two species of mosquitoes revealed thatCulex vishnui was more inclined to human blood (21·5%) than that ofCulex pseudovishnui (16·14%).Culex vishnui andCulex pseudovishnui were both susceptible to DDT, dieldrin and malathion, but the LT50 value was slightly higher in the former species than the latter.Culex vishnui utilised its breeding spots like paddy fields, ponds, ditches and burrow-pits more effectively in almost all the months of a year thanCulex pseudovishnui. The density of the larvae ofCulex pseudovishnui was found to be lower than that ofCulex vishnui. Japanese encephalitis virus was isolated only fromCulex vishnui in West Bengal.
pp 637-646 September 1987
Previous work on the importance of egg ultrastructure to the taxonomic and phylogenetic studies of Ephemeroptera with special emphasis on the two schistonotan families, Leptophlebiidae and Heptageniidae is reviewed. The chorionic sculpturings, the types of micropyles and attachment structures of the eggs of south Indian mayfly species belonging to 8 genera of Leptophlebiidae and 3 genera of Heptageniidae have been studied through scanning electron microscope.
The present study confirms the earlier observations that the Leptophlebiidae are most certainly of enough distant relationship with the Heptageniidae to warrent inclusion in separate superfamilies viz Leptophlebioidea and Baetoidea. Whereas the structural modifications on the eggs are significant in contributing to the taxonomy of both the families at the generic level, submicroscopic examinations of chorionic structures provide data for the separation of different species and species complexes in Leptophlebiidae.