A comparative study of larval cannibalism in three species of ladybird

Abstract. 1. Cannibalism was studied under laboratory conditions in three species of Coccinellidae (Coleoptera): Cycloneda sanguinea , Olla v-nigrum , and Harmonia axyridis . Larval cannibalism varied among species, C. sanguinea  > H. axyridis  ≥  O. v-nigrum .
2. Larvae of all species cannibalised more in response to reduced food availability (14 h starvation daily) than in response to reduced food quality (dry Ephestia eggs).
3. Larvae of H. axyridis cannibalised siblings at lower rates than non-siblings, but larvae of C. sanguinea and O. v-nigrum did not. Rates of cannibalism increased significantly with increasing size disparity among larvae of all three species.
4. Cannibalism in C. sanguinea and H. axyridis , but not in O. v-nigrum , increased with larval density, suggesting that not all attacks on conspecifics are driven by hunger.
5. Costs, not benefits, were the predominant effects of exclusively and partially cannibalistic diets. A diet of conspecific eggs yielded survival equivalent to the Ephestia egg diet for H. axyridis and O. v-nigrum , but developmental time was extended and adults were smaller. Larvae of C. sanguinea had superior survival and faster development on conspecific eggs than on the Ephestia egg diet. Only H. axyridis larvae survived as well on diets comprised exclusively or partially of conspecific larvae as on Ephestia eggs, although they developed more slowly.     

Key to the New Zealand species of Psyllaephagus Ashmead (Hymenoptera: Encyrtidae) with descriptions of three new species and a new record of the psyllid hyperparasitoid Coccidoctonus psyllae Riek (Hymenoptera: Encyrtidae)

Abstract  This paper records seven species of wasps in the genus Psyllaephagus (Hymenoptera: Encyrtidae) from New Zealand. All of these species are primary parasitoids of psylloids (Hemiptera: Psylloidea). Two are species previously described from New Zealand: P. acaciae Noyes and P. pilosus Noyes. Two are described Australian species which have established recently: P. bliteus Riek and P. gemitus Riek. Three new species are described here, from New Zealand: P. breviramus sp. nov., P. cornwallensis sp. nov. and P. richardhenryi sp. nov. All species are probably Australian in origin. A key to all seven Psyllaephagus species known from New Zealand is provided. An earlier first record of the Australian psyllid hyperparasitoid Coccidoctonus psyllae Riek (Hymenoptera: Encyrtidae), previously first recorded from New Zealand in 2006, is noted.     

Genetic identification of morphologically cryptic agricultural pests

1 Wireworms are the polyphagous larvae of click beetles and are well known as agricultural pests. Larvae of the genus Agriotes are internationally recognized as economically important pests of potato. Historically associated with crop damage after conversion of grassland, they are an increasing problem even in all-arable rotations.
2 Current studies of Agriotes ecology and behaviour, and consequently control and management, are seriously hampered by the lack of a means of reliably identifying larvae owing to morphological crypsis during this life-stage.
3 Here, sequence data at the mitochondrial 16SrRNA gene are presented for three species of wireworm: Agriotes obscurus, A. lineatus , and A. sputator. A novel terminal restriction fragment length polymorphism (T-RFLP) technique is described that identifies larvae of these species. This technique is shown to be both efficient and reliable. Interestingly, thus far the samples tested have yielded no A. lineatus. Implications for future study of wireworm ecology and control are discussed.     

Revision of the Australian species of Hyalobathra Meyrick (Lepidoptera: Pyraloidea: Crambidae: Pyraustinae) based on adult morphology and with description of a new species

Abstract The genus Hyalobathra Meyrick is redefined based on five Australian species including the type  species. The four named Australian species, H. archeleuca Meyrick, H. unicolor (Warren) , H. miniosalis (Guenée) and H. minialis (Warren), are redescribed and a new species, H. crenulata sp. n., is described . Hyalobathra unicolor is removed from synonymy with H. illectalis (Walker), and lectotypes are designated for H. archeleuca , H. minialis and for H. rhodoplecta Turner, a synonym of H. miniosalis . The presence of H. paupellalis (Lederer) in Australia could not be confirmed, but its genitalia are figured. Two previously included species, ' Hyalobathra ' aequalis (Lederer) and ' H .'  brevialis (Walker), are excluded from Hyalobathra, as they lack its generic apomorphies, but cannot at present be assigned to any other genus.     

Predation efficiency of indigenous larvivorous fish species on Culex pipiens L. larvae (Diptera: Culicidae) in drainage ditches in Argentina.

Two neotropical freshwater fish species, Cnesterodom decemmaculatus (Poeciliidae) and Jenynsia multidentata (Anablepidae), were collected from human-made ditches, a common habitat of the house mosquito Culex pipiens in La Plata, Argentina. Cnesterodom decemmaculatus was recorded in 62 of the 100 examined ditches, whereas J. multidentata was collected from only 21 ditches sympatrically with C. decemmaculatus. Culex pipiens was the only mosquito species collected, and its larvae and pupae were found in 38 of the 100 ditches. Fish and mosquito larvae and pupae were collected together in only two ditches and were significantly negatively correlated. Siphons of larval Culex and remnants of chironomid larvae, copepods, aquatic mites, and fish were present in the gut contents of two C. decemmaculatus from mosquito-positive ditches, while diatoms and filamentous algae were recorded in every fish dissected. Adult C. decemmaculatus and J. multidentata needed approximately 6.2 h to completely digest one Cx. pipiens 4th instar larva under laboratory conditions. When fish were confined with a density of 60 or fewer Cx. pipiens 4th instar larvae, C. decemmaculatus and J. multidentata adults consumed 100% of them in one day but only 35% and 42%, respectively, when confined with 150 larvae. Eradication of Cx. pipiens from a ditch, where densities had averaged 250 immatures per dip, was achieved 17 days after the introduction of 1,700 C. decemmaculatus.     

Delivery of hatching larvae to estuaries by an amphidromous river shrimp: tests of hypotheses based on larval moulting and distribution

1.  Amphidromous shrimps live and breed in freshwater rivers and streams, but their larvae require development in sea water. Larvae may hatch upstream and then drift to the sea, although in some species females have been reported to migrate to the coast before larvae are released. Here, we tested the relative importance of larval drift and female migration in Macrobrachium ohione (Decapoda: Palaemonidae) in a distributary of the Mississippi River in Louisiana, U.S.A.
2.  Newly hatched (stage-1) larvae are nonfeeding and will not moult to stage 2 (first feeding stage) without encountering salt water. A factorial experiment was conducted in the laboratory to test the effects on moulting to stage 2 of (i) time spent by stage-1 larvae in fresh water before (ii) exposure to and maintenance in water of different salinity. Larvae kept in fresh water for 1 or 3 days before a change to saline water at 6 or 10 ppt showed a greater frequency of moulting than those kept for longer (5 days) in fresh water or changed to less saline water (2 ppt). Non-moulting larvae died or were moribund within 11 days of hatching.
3.  The relative abundance of stage-1 larvae was measured with plankton tows at two locations in the river c. 150 km apart, one near the sea and one upstream. Larval abundances near the sea were significantly greater than those upstream.
4.  The results indicate that hatched larvae of M. ohione have a limited period in which to drift in fresh water before reaching water sufficiently saline to stimulate moulting to the first feeding stage. Female migrations may play an important role in delivering larvae of amphidromous species from large continental river systems in which distances to the sea are great, while larval drift alone may be sufficient in species living in short streams, like those found in many small mountainous tropical islands.     

Interactions between introduced and native predatory ladybirds (Coleoptera, Coccinellidae): factors influencing the success of species introductions

Abstract.  1. Why some exotic species invade successfully while others do not is poorly understood. This study focuses on the inability of the exotic predatory ladybird Adalia bipunctata (L.) (Coleoptera, Coccinellidae) to establish and spread in Japan. In particular, this study considers the interactions between A. bipunctata and three native Japanese ladybird species, Harmonia axyridis Pallas, Coccinella septempunctata Linn., and Propylea japonica Mulsant.
2. The number of aphids occurring on the host plants declined dramatically over the course of larval development in the presence of H. axyridis or C. septempunctata . In contrast, many aphids remained at the end of the experiment when only A. bipunctata or P. japonica was present.
3. The survivorship of A. bipunctata from second instar to adult was significantly reduced in the presence of H. axyridis , but not in the presence of C. septempunctata or P. japonica . Most deaths were the result of intra-guild predation when H. axyridis or C. septempunctata larvae were present. Larvae of H. axyridis and C. septempunctata suffered very high mortality in this experiment, but survived better when co-occurring with A. bipunctata than when occurring only with conspecifics. In contrast, P. japonica survived better when occurring with conspecifics than with A. bipunctata .
4. The finding that larvae of the exotic species A. bipunctata died at high rates from intra-guild predation by the native Japanese ladybirds H. axyridis and C. septempunctata may bear on the question of why A. bipunctata has not established more successfully in Japan whereas H. axyridis and C. septempunctata have been very successful in establishing themselves in North America.     

Predaceous diving beetle, Dytiscus sharpi sharpi (Coleoptera: Dytiscidae) larvae avoid cannibalism by recognizing prey

Larvae of diving beetles such as the various Dytiscus species (Coleoptera: Dytiscidae) are carnivorous and usually prey on other aquatic animals. Cannibalism among larvae of Dytiscus sharpi sharpi (Wehncke) was observed to begin when they were starved for more than two days under artificial breeding conditions. However, the 2-day starved larvae did not show cannibalism in the presence of intact, motionless, frozen tadpoles, or frozen shrimps. The beetle larvae attacked and captured intact tadpoles faster (15 sec) than other motionless and frozen tadpoles (120 sec), indicating that prey movement was an important factor in stimulating feeding behavior in larvae. Prey density does not have an effect on larval cannibalism. In cases in which preys are present at lower densities than that of larvae, a group of beetle larvae frequently fed on single prey. This feeding behavior, therefore, provides direct evidence of self-other recognition at the species level. Using two traps in one aquarium that allows the larvae to detect only prey smell, one containing tadpoles and another empty, the beetle larvae were attracted to the trap with tadpoles at high frequency, but not to the empty trap. In another experiment, the beetle larvae were not attracted to the trap containing a beetle larva. These results suggest that the larvae of D. sharpi sharpi are capable of recognizing prey scent, which enables the promotion of foraging behavior and the prevention of cannibalism.     

Survival at low temperature of larvae of the pine processionary moth Thaumetopoea pityocampa from an area of range expansion

1 Larvae of Thaumetopoea pityocampa (Lepidoptera: Notodontidae) develop throughout the winter, although their feeding activity and survival can be impaired by adverse climatic factors. The present study investigated the survival at low temperature of larvae originating from a population with range expansion in an alpine valley in Northern Italy.
2 The supercooling point of individually analysed larvae averaged at −7 °C. This value insufficiently described the cold hardiness of the larvae; 39% of the tested larvae were alive when returned to room temperature immediately after freezing. When larval colonies inside their nest were exposed to −17 °C for 1 h after gradual temperature decrease, survival was 70.4%.
3 Rearing of larvae in the laboratory at different day/night temperatures indicated an effect of cumulative chill injury on larvae. A logistic regression explained the relationship between negative thermal sum (h°C below 0 °C) received in the laboratory experiment and larval survival. A similar relationship was demonstrated between negative thermal sum and survival of larval colonies in the field.
4 In the laboratory experiment, some tested larvae were able to survive for up to 8 weeks without feeding depending on rearing temperature. As expected, feeding occurred only when larvae were reared at temperatures of 9 °C day/0 °C night.
5 We classify the larvae of T. pityocampa as being moderate freezing tolerant. The winter behaviour allows this species to track climate warming by a rapid expansion into those areas that become compatible with the insect's development.