Biosystematics of Tingidae on the Basis of the Biology and Micro Morphology of Their Eggs*
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Proc. Indian Acad. Sci. (Anirn. Sci.), Vol. 96, No. 5, September 1987, pp. 587-611. (D Printed in India. Biosystematics of Tingidae on the basis of the biology and micro morphology of their eggs* DA YID LIYINGSTONE and MHSYACOOB Division of Entomology, Bharathiar University, Coimbatore 641 046, India Abstract. 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 ha ve 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 thc 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. Keywords. Tingidae; oviposition strategies; opercular diversities; evolutionary trend; biosystematics. I. Introduction The pioneering contribution of Southwood (1956) on the classification of Terrestrial Heteroptera on the basis of egg structure and the classic monograph of Cobben (1968) on the evolutionary trends in Heteroptera on the basis of the micromorpho logy of the eggs, continue to challenge those who try to venture on the biosystema tics of any particular family of Heteroptera. Unfortunately, the posthumously published 3 volume treatise of Hinton (198 I) on the biology of the insect eggs, but for the third volume comprising of the bibliography, has nothing substantial to offer on the biology of the eggs of Heteroptera. Nevertheless, the contributions of Salkeld (1972) and Haridass (1985a, b, 1986a, b) on the ultrastructure of reduviid eggs have enormously enhanced the scope of future attempts on the biosystematics of Cimico morpha in general on the basis of the biology and micromorphology of their eggs. The Tingidae, constituting a minor family of Heteroptera, ever since Johnson (1936) published the first elaborate account of the biology of the Rhododendron lace bug. Leptobvcrsa rhododendri, has been steadily registering its importance as a 'Contribution No. 44. SR7 588 David Livingstone and M H S Yacoob weed control agent, as a potential vector of coconut wilt and as a rare example of floral gallmaker. The biology and micromorphology of the eggs of Tingidae has been considered in specific cases of biological studies, attempted by Roonwal (1952) on Teleonemia scrupulosa: Stusak (1961, 1968), on Monanthia symphyti; M. rotundata; Acalypta marginata; A. parvula; A. corynata; Elasmotropis testacea: Catoplatus [abricit; Physatocheila dumetorum; Deryphysia foliacea; D. catoplatus; Tinqis auriculata; T. reticulata and T. stachydis, Livingstcne (1959, 1962a, b, 1967a, 1968, 1976) on Urentius euonymus; M onosteira minutula; Cadmilos retiarius; Tinqis buddleiae and Dasytingis rudis and Livingstone and his eo-workers (Livingstone et al 1981; Livingstone and Yacoob 1983a, b, 1986) on Pontanus puerilis, Agramma spp. and A. hupehanum. The more recent publications of Yaccoob and Livingstone (1983) and Livingstone and Yacoob (1983a, b, 1986) on the egg Parasitoids of a miscellany of Tingidae of southern India provide adequate informations for placing emphasis on the biology of the eggs as a significant aspect of biosystematics. In the present paper, the micromorphology and biology of the eggs of 40 species of Tingidae belonging to 26 genera and two subfamilies of southern India provide the bases for assessing the biosystematics of this family. 2. Oviposition site selection and oviposition strategy Tingidae are by and large species specific in their host selection (Livingstone 1977). They feed and oviposit on the same host plant. But each species selects its own oviposition site and accordingly their strategies of oviposition vary. All species of southern India whose biologies are known are multivoltine. Even the exotic species T. scrupulosa, the Lantana lace bug, which is known to be bivoltine in northern India (Khan 1945; Roonwal 1952), is multivoltine in southern India, breeding all round the year, producing more than 12 generations (Livingstone et al 1980). Most European species of tingids are known to be bivoltine (Drake and Ruhoff 1965). The British thistle lace bugs, Tinqis ampliata and T. cardui are reported to be univoltine. However, their overwintering phenomenon is not well understood (Eguagie 1972a, b, 1973, 1974a, b). All the 4 known species of the subfamily Vianaidinae are reported to be myrmecophilous and but for a meagre fragmentary information on the micromorpho logy of the ovariolar egg of one species (Cobben 1968) their biologies are not known. The gallicolous species of Copium and Paracopium are anthophagous and they oviposit into the corolla by rotating their eggs in their oviduct at 180°, so that while ovipositing, the operculum could be directed to the interior of the flower bud. The nymphs that hatch enter the space beneath the corolla and make the monothalamus floral cecidium (Darke and Davis 1960; Darke and Ruhoff 1965). This unique rotatory mechanism of the eggs in these bugs is not even vaguely understood from the reports of Fischer (1956), Monad and Carayon (1958), Abraham and Abraham (1971) and Jaeger (1976). Specificity in oviposition site selection on the host plant is strongly indicated as revealed in table 1 and the manner of oviposition is determined by the oviposition site. as indicated in table 2. The manner of oviposition is further indicated by the specialization of the ovipositor (figure 5). Such specializations become species specific and such an explorative study provides valuable information on the biosysternatics, Biosystematics of Tinqidae 589 inter-specific relationships and adaptive radiation of this or any other group of insects. 2.1 Lamina oviposition Depending on the thickness and architecture of the lamina or the calyx, the eggs are inserted either parallel (horizontal) to the leaf surface as in all the grass tingids such as Aconchus urbanus, Agramma spp. and other monocot tingids such as Stephanitis spp. or slantingly into the mesophyll as in the majority of lamina ovipositing species (figure 3J). The degree of obliquity is directly related to the relative thickness of the lamina. Tingids of the verbenaceous plants tend to insert their eggs near to vertical position, similar to those that insert their eggs into stems and pistils. Horizontal deposition in monocot lamina invariably occurs in between parallel veins. In lamina oviposition, since the eggs are inserted into the substance of [he leaf, the upper and lower epidermis turn transparent, and the site of oviposition becomes dechlorophylled, betraying the presence of the egg. All the lamina depositors show varying degrees of preference to specific sites such as dorsal surface, ventral surface, leaf margin and leaf tips (table I) and majority of them prefer the ventral surface, for safety and protection from direct exposure to sun light. It has also the advantage of the safety of the nymphs from predators and from being directly exposed to insecticides. The first gonapophysis of the lamina ovipositors can be readily recognized by the arrangement of serrations, especially in the grass tingids, for facilitating insertion into the flaccid blades (figure 5 J-Nl. 2.2 Rachis/petiole/vein oviposition Considerable variations occur in the degree of obliquity of oviposition, depending on the thickness of the substrate. When the eggs are deposited into the midrib they are closer to vertical insertion as in Pontanus puerilis (figure 3G) and Perissonemia ecmeles (figure 3E). 2.3 Floral parts oviposition There is specificity in the selection of floral parts also. C. retiarius selects the calyx (Livingstone 1962b). D. rudis (Livingstone 1976), D. semota and Ammianus ravanus specifically select tender pistil and oviposit in clusters of 3-8 eggs. The eggs hatch before the pistil matures since mature fruits always carry shells .01' hatched eggs. 2.4 Stem oviposition This is characteristically found in C. bullita, inserting its eggs vertically in batches of more than IQ eggs per batch into the tender stems of Ocimum spp. Lamina oviposition is also not uncommon in this species, as reported by Samuel (1939) and Sharga (1953). Phatnoma costalis alone has been found ovipositing exclusively into the tender stems of Hibiscus. In C. retiarius, a polyphagous