André Ferran

Antennal sensilla and sexual dimorphism of the adult ladybird beetle Semiadalia undecimnotata Schn. (Coleoptera: Coccinellidae)

The antennal receptors of the adult male and female ladybird beetle, Semiadalia undecimnotata (Coleoptera: Coccinellidae), were examined by scanning and transmission electron microscopy. Twelve types of receptors were characterized and grouped into 5 morphological classes: Bohm, trichoid, coeloconic, basiconic, and chetiform sensilla. Sensory function was determined on the basis of sensillar ultrastructure and electrophysiological response. Olfactory sensilla are confined in both sexes to the 2 terminal antennal segments. In contrast, gustatory and mechanosensitive organs are present along the entire length of the antennae. Sexual dimorphism of antennal receptors is limited to the latter 2 functional classes. The principal characteristics of this dimorphism are the following: a) males possess 540 sensilla (all types), while females possess only 500; b) males exhibit 2 types of taste receptors not present in females; c) females exhibit one type of mechanoreceptor absent in males; d) the 3 sex-specific types of sensilla, which occupy the same position in males and females, are confined to the inner side of the antennae. The possible role of male-specific sensilla in intersexual communication is discussed.

A natural flightless mutation in the ladybird, Harmonia axyridis

A homozygous flightless strain, obtained by selection from a laboratory population of Harmonia axyridis Pallas (Coleoptera, Coccinellidae), has been reared under controlled conditions since 1982 after sampling in China. The adults of this flightless strain have normal elytra and wings but drop almost vertically when they attempt to fly. The origin of this mutation, whether laboratory or natural, is discussed. As the mutation does not affect the fitness of the beetles, this flightless strain can be used in biological control. Releasing flightless adults rather than larvae should provide the potential for more continuous control of aphids by both larvae and adults.

Locomotory behavior of flightless Harmonia axyridis Pallas (Col., Coccinellidae).

To improve the efficiency of the lady beetle H. axyridis as a biological control agent against aphids, a flightless population was obtained by feeding adults with a mutagen and selecting their progeny for nonflying but otherwise morphologically normal individuals. These flightless adults attempted to fly but immediately fell. They softened their fall by opening their elytrae and wings. The inability to fly could result from change in their flying behavior compared to control adults. The flight duration was very much shorter, and the wing beat frequency and, more particularly, the amplitude of the wing beats were clearly lower. More time was spent in the other components of the flight behavior such as wing rotation, wing immobility, and wing folding. The sequence of these patterns differed slightly, due mainly to change in their frequency. The locomotor behavior was not modified by the mutation, which affected only the wing muscles. Searching behavior of mutant adults differed from that of control adults only in that they took longer to encounter and ingest aphids. Nevertheless, the larval growth and reproductive rate remained unchanged. The behavioral and biological features of these flightless adults indicate that it should be possible to use them in biological control programs.

Morphology and ultrastructure of integumentary glands of Semiadalia undecimnotata schn. (Coleoptera : Coccinellidae)

Abstract The ultrastructure of integumentary glands of the adult ladybird, Semiadalia undecimnotata (Coleoptera : Coccinellidae) is described. Two types of glands can be found distributed over the head, thorax, and abdomen: glands without ducts and glands with secretory ducts. Glands without ducts consist of a single cell and a secretory apparatus located within the thickness of the cuticle and equipped with a cuticular cribriform plate; this cribriform plate separates 2 superimposed cavities, and epicuticular filaments fill the lower cavity. Glands without ducts are thought to release volatile pheromones. Glands with a duct appear to be made of 2 kinds of cells: one cell forms the receiving duct and later synthesizes the secretory products, one (or more) cell makes the evacuating duct. Their secretions are abundant and released on the surface of the cuticle in the shape of tortuous cylinders, which are resistant to acetone treatment. Glands without ducts and glands with secretory ducts correspond, respectively, to classes 1 and 3 gland cells according to the nomenclature of Noirot and Quennedey (1974, Annu. Rev. Entomol. 19 : 61–80).

Taste Sensitivity of Detritivorous Mosquito Larvae to Decomposed Leaf Litter

Dietary leaf litter chemistry is known to play an important ecotoxicological role in the plant–mosquito interaction in subalpine flooded areas surrounded by vegetation because of differential larvicidal effects of insoluble polyphenols formed during the leaf decaying process. This dietary interaction was investigated through comparative evaluation of the role of toxic/nontoxic leaf litter in both larval foraging and feeding behavior, by using different samples of decomposed alder leaf litter and larval Aedes aegypti as experimental references. Track analysis showed significant differences in larval foraging behavior in the absence or presence of leaf litter. Comparative alimentary preference investigations and further track analysis suggested that larvae are unable to detect leaf litter toxicity. These characteristics of the larval behavioral feeding pattern suggested that: (1) decomposed leaf litter may be involved as an important attractive food source in the habitat selection and evolutionary history of culicids, and (2) preingestive behavioral mechanisms appear to be minimally involved in the differential larval dietary adaptation to toxic leaf litter. These results may have interesting consequences for culicid biological control.

RETRACTED: Locomotory behavior of flightless Harmonia axyridis Pallas (Col., Coccinellidae)

To improve the efficiency of the ladybeetle Harmonia axyridis as a biological control agent against aphids, a flightless population was produced by feeding adults with a mutagen and selecting their progeny for non-flying but otherwise morphologically normal individuals. The inability to fly could result from a change in their flying behavior compared with control adults. Flight duration was very much shorter, wing beat frequency and more particularly the amplitude of the wing beats were clearly lower. More time was spent on the other components of flight behavior such as wing rotation, wing immobility and wing folding. The sequence of these patterns differed slightly mainly due to changes in their frequency. The locomotory behavior was not modified by the mutation, which only affected the wing muscles. The searching behavior of mutant adults differed from that of control adults only in that they took longer to encounter and ingest aphids. As this difference is not important, it should be possible to use this flightless population in biological control programs.