Ivo Hodek

Ecology and Behaviour of the Ladybird Beetles (Coccinellidae): Hodek/Ecology and Behaviour of the Ladybird Beetles (Coccinellidae)

This book of 561 pages explores the amazing world of coccinellids, also known as ladybirds, ladybugs or lady beetles, and will appeal to both professional entomologists and amateurs. The important role played by coccinellids in biological control is chronologized since the successful introduction of the vedalia beetle, Rodolia cardinalis, into Californian citrus orchards in 1888–89, to control cottony cushion scale. The vedalia beetle saved the California citrus industry and has since been exported to many other parts of the world with equally successful results. For this reason, the ladybird has become an iconic symbol of classic biological control. Aside from their practical uses in biological control, including augmentation and conservation, the Coccinellidae are a very important group in ecology and are often used as a model systems in biology classsrooms and in many entomological studies. All scientists involved in applied ecology and pest control sooner or later need to deal with ladybugs and these insects are studied worldwide by many research groups. Also, because of their attractive appearance and public appeal, many amateurs collect and study them. Although there are a number of books on coccinellids, this compilation is a state of the art treatment of their biology, ecology and behavior. The editors are among the most important coccinellid specialists in the world, and this book comprises a major revision of previous editions with 12 chapters written by 14 different contributors. It covers all biological aspects of the Coccinellidae, including phylogeny, genetics, life history, distribution in habitats, food relationships, diapause, intraguild interactions, natural enemies of lady beetles, semiochemicals, quantification of their impact on prey, biological control, and recent developments and future trends in the study of these insects. The book begins by detailing recent developments in two basic disciplines, “Phylogeny” and “Genetics”, which are often neglected by ecologists and pest control specialists. Subsequent chapters address topics important to understand and interpret the role of Coccinellids in their habitats and present detailed updates on the subject matter, including summary tables that facilitate the synthesis of large amounts of data. All these topics are presented in a perspective of Coccinellid conservation and approaches to habitat and landscape management are provided. In the subchapter on “Food Specificity” (pp. 157–165), the relationships of coccinellid species to their prey is analysed by comparing examples of toxic and rejected prey (mostly aphids) to those that represent suitable food. Prey suitability cannot be estimated simply by acceptance, because toxic prey are also consumed (pp. 145–147). It is stressed that the quality of food should be considered in terms of its physiological/nutritional suitability and whether it supports complete development and successful reproduction. The chapter on “Intraguild interactions” deals with a very debated and controversial topic with implications for ecosystem functions, pest control and the potential impacts of exotic species. The chapter on “Biological Control” is an exhaustive review on the role of coccinellids in controlling pests and covers numerous examples of importation, augmentation and conservation. In this chapter, the reader can also find interesting ecological contrasts between coccidophagous and aphidophagous coccinellids that are construed to account for their differential impacts on coccids versus aphids. This section contains also a table summarizing insecticides that have some degree of selectivity for coccinellids, which is of importance in the context of IPM. “Quantifying the Impact of Coccinellids on their Prey” is another important topic, and this chapter outlines recent molecular tools which can assist such studies, in addition to reviewing conventional approaches. “Natural Enemies of Coccinellids” and “Semiochemicals” are approached from an ecological perspective and provide a comprehensive summary of these topics. In particular, the chapter on “Natural Enemies of Coccinellids” contains clear tables and charts which help the reader synthetize all the information. The chapter “Semiochemicals” and the subchapter “Food Related Behaviour” explore the potential of specific molecules to manipulate coccinellid behaviour. In contrast to earlier views that foraging is a random process, evidence is now presented that coccinellids are guided by olfactory and visual cues (pp. 223–226). Another breakthrough is the discovery of oviposition deterrence; ladybird females avoid the trails of conspecific larvae because they pose a risk for egg cannibalism (pp. 228–232). The last chapter is dedicated to future trends in research, which makes it interesting for specialists and ecologists, and also to those just beggining study of these insects, including students and young researchers. The lacunae in knowledge and needs for future research are treated with clarity and accuracy, which encourages and motivates the reader towards studying this important group. At the end of the book, an appendix contains the “List of Genera in Tribes and Subfamilies”. The contents are really detailed (as indicated in the book of Coccinellidae), and this is very useful and practical aid for reader orientation among the many topics covered, facilitating a comfortable read. This is also aided by the use of bold print to highlight key terms throughout the text.

The effects of thirteen species of aphids on some life history parameters of the ladybird Coccinella septempunctata

The prediction of impact ofcoccinellids in an aphid infested crop dependson the food specificity of the predator. Theresponse towards thirteen species of aphids(Sternorrhyncha: Aphididae) was thereforetested in the most abundant aphidophagouscoccinellid Coccinella septempunctata L.(Coleoptera: Coccinellidae). All aphidspecies studied (Eucalipterus tiliae(L.), Tuberculatus annulatus (L.), Euceraphis betulae (L.), Cavariellakonoi Takahashi, Liosomaphis berberidis(Kaltenbach), Acyrthosiphon ignotumMordvilko, Aphis spiraephaga Müller,Aphis fabae Scopoli, Macrosiphoniella artemisiae Boyer de Fonscolombe, Capitophorus hippophaeus(Walk.), Acyrthosiphon pisum (Harris),Aphis craccivora Koch, Sitobionavenae (Fabricius) were suitable foodaccording to the rate of larval development,larval mortality and adult fresh weight.Females of C. septempunctata fed with A. pisum and S. avenae laid twice as manyeggs as those fed with A. fabae and A. craccivora. These data are needed foreffective mass rearing of the studiedcoccinellid species.

Geographic variation in diapause response of adult Rhipicephalus appendiculatus ticks

Diapause in adults of the African brown ear tick Rhipicephalus appendiculatus is dependent on latitude and stock origin. Lower latitude populations, that is, those nearer the equator, show no diapause response to long or short day exposure. Diapause response to short day lengths is found in higher latitude populations, further south, and increases with increasing latitude. Nearly all individuals in the southernmost population, used in this study, enter diapause under short and long day exposure which implies that the onset of diapause in this population is obligatory. Diapause termination in higher latitude populations is induced by increasing photo period, further north, but still south of the equator, diapause is terminated by ageing. The differences in diapausing behaviour of the different populations are discussed in relation to their climatic conditions.

Intermittent character of adult diapause in Aelia acuminata (Heteroptera)

Abstract The response to photoperiod of field-collected Aelia acuminata was studied by exposing insects to three photoperiodic regimes. After the completion of diapause the insects do not respond to photoperiod: in mid-February the length of the pre-oviposition period is the same under both long and short photoperiods. After the onset of oviposition, insects again become responsive to photoperiod regardless of the time of year: under long day, oviposition lasts until death, whereas under short day the females cease oviposition after about 3 weeks. After a further 2 or 3 months without ovipositing, these females which are still experiencing short-day conditions resume reproduction for a further 4–7 weeks and long-lived individuals have three oviposition periods. A regulatory mechanism is suggested for the alternation between oviposition and diapause.

Control of diapause and supercooling by the retrocerebral complex in Pyrrhocoris apterus

Effects of external (photoperiod, temperature) and internal (retrocerebral complex, diapause condition) factors on supercooling were studied in Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae) adults. An increase in supercooling capacity is associated with the induction of diapause by short‐day photoperiod or cardiacallatectomy of long‐day non‐diapause insects in spite of a high temperature of 26 °C. The induction of diapause is a prerequisite for a further increase in supercooling capacity by cold acclimation.

Sensitivity of larvae to photoperiods controlling the adult diapause of two insects

Abstract The sensitivity of larvae of Pyrrhocoris apterus to photoperiods controlling the adult diapause was studied by changing light conditions at various larval ages. A high proportion of adults oviposited, even when the diapause-preventing exposure of a long-day regimen (L 18, D 6) was changed 2 days before the adult ecdysis to the diapause-inducing short day (L 12, D 12). The reverse procedure resulted in all adults laying eggs. The pre-oviposition period then gradually decreased with the prolongation of the diapause-preventing treatment of larvae. The responsiveness of larvae of Leptinotarsa decemlineata was proved by keeping the adults at an intermediate photoperiod (L 14, D 10). The diapause-inducing effect of short-day conditions on the larvae was thus not reversed in adults, as occurs if the adults are exposed to the diapause-preventing long-day regimen. A general rule arises from the results. The responsiveness of larvae to the signals controlling the imaginal diapause is not excluded by oviposition of adults kept under photoperiods adverse to diapause. The effect of factors experienced by the larvae results in modification of the pre-oviposition period and of the incidence of diapause only when the adults are reared under neutral light conditions.

Anatomical and histological changes during dormancy in twococcinellidae

The gonads of both females and males ofSemiadalia undecimnotataSchneid, were studied during the estivo-hibernation period (August–May). The ovaries remain unripe in diapausing females, the ovarioles being formed by mere germaria until late April (or early May) when the previtellogenesis begins. In some years, the stage of the first oocyte is attained in females staying still in the hibernation quarters. On the contrary, both the spermatogenesis and spermateliosis proceed in the testes of diapausing males so long as the ambiant temperature is sufficiently high (August–September, April–May). Only in the coldest period of dormancy (November–March) the tissue of testicular follicles ceases to be active. Since mid-April the spermatogenesis and spermateliosis are resumed completely and the males fertilize the females, as is shown by dissections of their spermathecae. Seminal vesicles are always full of sperms. The digestive tract is empty in inactive coccinellids and the size of the fat body gradually diminishes in the course of estivo-hibernation.The dependence of the activity of the tissue of testicular follicles on the ambient temperature was proved experimentally in bothS. undecimnotata andCoccinella septempunctata L. The temperature of +12°C enables a natural regression, while an abrupt transfer to +5°C renders gradual emptying of follicles impossible.RésuméLes femelles et mâles deSemiadalia undecimnotataSchneid., récoltés dans les quartiers d’estivo-hivernation dans les collines de Louny (Bohême du Nord) furent disséqués pendant la période de repos de cette espèce (du mois d’août au mois de mai).Les femelles présentent en permanence des ovaires immatures dont toutes les ovarioles se réduisent aux seuls germaria. Les premiers ovocytes apparaissent au milieu de mai. Selon les années, cette période de prévitellogenèse peut être observée même sur les lieux d’hibernation. On observe des spermathèques vides pendant presque tout le repos, sauf au printemps. Depuis le commencement d’avril jusqu’au moment de la migration de retour, le pourcentage de femelles avec une spermathèque qui contient des spermatozoïdes actifs augmente graduellement jusqu’à atteindre 100%.Par contre, comme chez les mâles la spermatogenèse débute au stade nymphal, l’activité des tissus des follicules testiculaires se poursuit au cours des deux premiers mois de leur estivo-hibernation (août et septembre). A la fin de septembre et pendant le mois d’octobre la quantité des éléments cellulaires diminue en fonction de la diminution de la température. Pendant la période au climat le plus froid (de novembre à mars), la spermatogenèse s’arrête et les follicules testiculaires deviennent presque vides, à l’exception de leur partie distale qui contient quelques ovogonies et de leur portion proximale qui renferme les faisceaux de spermatozoïdes. En avril, la spermatogenèse reprend; pour cette raison, à partir de la miavril tous les mâles présentent une activité normale des follicules testiculaires qui leur permet de fertiliser les femelles.Parce que nous avons décelé une coïncidence entre la régression de l’activité des follicules testiculaires et la diminution de la température, nous nous sommes attachés à préciser expérimentalement cette relation chezS. undecimnotata etCoccinella septempunctata L. Aux températures élevées, obtenues au laboratoire (25°C), mais également aux températures alternées (entre 17 et 22°C ou entre 12 et 20°C), l’activité des follicules testiculaires peut se maintenir ou reprendre, si on assure une nourriture miellée. Par contre, une température constante de 12°C détermine une régression normale de l’activité. Le brusque transfert des mâles aux températures qui avoisinent le zéro (+5°C const.) ne rend pas possible une régression de ce type et l’on observe des situations anormales.

Effect of thermoperiod on diapause intensity in Pyrrhocoris apterus (Heteroptera Pyrrhocoridae)

The intensity of adult diapause in Pyrrhocoris apterus was measured in two series of experiments as the duration of pre-oviposition period at a constant temperature of 25 degrees C after transfer from short (12L:12D) to long day conditions (18L:6D). Higher diapause intensity was induced with a thermoperiod than at constant temperatures. After the induction throughout larval instars 3-5 and during 4 weeks of adult life at short days and a thermoperiod of 25/15 degrees C the pre-oviposition period was 30+/-4 and 26+/-3 days. After induction at constant 25 degrees C the pre-oviposition period was 22+/-3 and 23+/-4 days, while after induction at constant 20 degrees C it was 17+/-4 and 19+/-4 days. Induction at a lower constant temperature of 20 degrees C was thus followed by a less intense diapause than the induction at a higher constant temperature of 25 degrees C. These counterintuitive results are discussed. The oxygen consumption rate measured at experimental temperatures prior to transfer from short to long days was higher at thermoperiodic conditions than at constant temperatures and it was similar at constant 20 and 25 degrees C. Thus, the oxygen consumption rate measured prior to the transfer was highest (indication of the least intense diapause) in the insects that showed later, after the transfer to long days, the longest pre-oviposition period (indication of the most intense diapause). Within the first two days after transfer to constant 25 degrees C, oxygen consumption rate measured at 25 degrees C decreased in the thermoperiodic insects, while it transiently increased in insects from constant 20 degrees C. Two days and later after the transfer, oxygen consumption rate was similar in all groups. Cold hardiness was not correlated with diapause intensity. The low lethal temperature in diapausing insects was correlated with the night temperature during diapause induction.

Adult Diapause in Coleoptera

Recent studies dealing with adult (reproductive) diapause in the Coleoptera are reviewed, as a kind of supplement to the classic compendia. In the first two sections, the general characteristics of adult diapause are described and principal terms explained. Original articles dealing with 19 species from nine coleopteran families (Coccinellidae, Chrysomelidae, Bruchidae, Curculionidae, Carabidae, Silphidae, Scolytidae, Scarabaeidae, and Endomychidae) are reviewed. Finally attempts are made at generalisations from the papers reviewed, and hypotheses on diapause evolution are inferred. A polyphenic character of diapause is a prominent feature in C. septempunctata and L. decemlineata, but has been found also in other Coleoptera and in insects generally and often generates voltinism heterogeneity within populations.

Mating and activity of gonads in pre-dormant and dormant ladybirds (Coleoptera: Coccinellidae)

Summary We checked voltinism tendencies in four ladybird species considered to be univoltine in Central Europe. The developmental state of male and female gonads and the incidence of mating females were investigated between September 1998 and April 1999 in ladybirds sampled from two localities in the Czech Republic: (1) in the vicinity of the town of Ceske Budejovice (S Bohemia) and (2) at the top of the hill Raná (N Bohemia). Interspecific differences in those aspects of reproductive activity were checked in the pre-dormancy/early dormancy period (September) in Ceratomegilla undecimnotata (Schneid.), Coccinella septempunctata L., C. quinquepunctata L. and C. magnified Redtb. Changes in the course of dormancy were monitored in C. undecimnotata and C. septempunctata. Since C. septempunctata from S Bohemia was relatively heavily parasitized by a braconid, Dinocampus coccinellae (Schrank), the effect of parasitization by this parasitoid on ladybird sexual activity was also analysed. In September, all C. undecimnotata females had completely inactive ovaries, and none of them had mated, while some females of Coccinella spp. displayed a certain degree of ovarian activity and many females had mated. The activity of testes varied greatly in all species, but the least active, on average, was C. undecimnotata. In both C. undecimnotata and C. septempunctata males, the mean activity of the testes considerably decreased between September and January and then increased in April. However, at each date it was significantly lower in C. undecimnotata than in C. septempunctata. The ovaries of some C. septempunctata females started to mature already in April, while all C. undecimnotata females still had inactive ovaries. C. septempunctata females parasitized by D. coccinellae were more often mated and more often snowed certain activity of ovaries than unparasitized ones. In males, however, parasitization caused reduction in the activity of gonads. It can be concluded that the entire central European population of C. undecimnotata is probably obligatorily univoltine, while in populations of the three Coccinella species some individuals are potentially multivoltine. Diapause and post-diapause development is modified, at least in C. septempunctata, due to parasitization by D. coccinellae.