On oviposition in weevils of the genus <Emphasis Type="Italic">Larinus</Emphasis> Dej. (Coleoptera,Curculionidae)

The following actions performed by females of several Larinus Dej. species during egg laying are described: search of an appropriate place on the plant, making the hole for the egg, oviposition proper, and sealing the hole. The hole preparation takes the longest time and the greatest effort. Only one individual usually completes development in one flower head. Females of Larinus vulpes Ol. prefer larger flower heads for oviposition and occasionally lay eggs into stems. The ability of females to distinguish the flower heads with already laid eggs is discussed. Species of Larinus may be divided into two groups with “early” and “late” oviposition. The evolution of egg laying in the genus Larinus is discussed.     

Phenology and dispersal of Larinus minutus Gyllenhal and Larinus obtusus Gyllenhal (Coleoptera: Curculionidae), two biological control agents of Centaurea stoebe ssp. micranthos (spotted knapweed) in Michigan

Centaurea stoebe L. ssp. micranthos (Gugler) (spotted knapweed) is an invasive plant that has been the target of classical biological control in North America for more than four decades. The seedhead-feeding weevils Larinus minutus Gyllenhal and Larinus obtusus Gyllenhal (Coleoptera: Curculionidae) are two of the most-widely released C. stoebe control agents, and have more recently been introduced into the eastern US. While there have been many studies focusing on their ability to impact C. stoebe in the western US and Canada, there have been few studies from eastern North America, and basic knowledge of important aspects of their biology is lacking. Here we report on the phenology and dispersal of L. minutus and L. obtusus in Michigan. We regularly sampled two established Larinus spp. populations in southern Michigan in 2012 and 2013, and found that while adult abundance fluctuates during the growing season, they remained at easily detectable levels from mid-June through the end of August. We also used previously established populations of L. minutus and L. obtusus released in 1996 (n = 1), 2007 (n = 2), and 2010 (n = 5) to determine how dispersal of Larinus spp. into the surrounding landscape changes with time since release. Populations of Larinus spp. weevils showed little dispersal for 2 years post-release. However, after initial establishment dispersal rates increased rapidly, resulting in average dispersal rates that increased exponentially with time since release. These findings can inform future biological control release and sampling programs for Larinus spp. in eastern North America.     

Allolarinus,a new genus and species of Lixini (Coleoptera: Curculionidae: Lixinae) from Congo

A new weevil genus, Allolarinus n. gen., with type species, Allolarinus demeyeri n. sp., is described from Congo in the tribe Lixini. The illustrations and diagnostic characteristics of this genus have been presented in a table and figure plates. This new genus is related to Larinus Dejean in terms of the type of elytra and general shape of the prothorax but clearly differs from Larinus with respect to its tooth-bearing femora and granulose pronotum. The trapezoidal short-neck prothorax and general shape of the elytra of this new genus are similar to those of Larinus; the granulose pronotum to that of Lixomorphus Faust; the dentate femora to that of Holcolixus Voss, Erilixus Voss, and Sublarinus Petri; while the existing cubito-anal vein on metathoracic wings to those of Allolixus Voss.     

Two new species of Larinus Dejean from North Africa (Coleoptera: Curculionidae), with a key to the striped Larinus (s.str.)

Two new sibling species, Larinus synthesys n. sp. from Algeria, and Larinus boroveci n. sp. from Algeria and Morocco, are described. Both species are tentatively assigned to the subgenus Larinus based on resemblance to species having longitudinal stripes on the elytra and rostrum. L. synthesys n. sp. is the smallest species in Larinus (s. str.) and is closely related to L. boroveci n. sp. The lectotype of Larinus cardopatii Lucas, 1847 is designated and redescribed. An illustrated key to the striped Larinus (s. str.) is given.     

The significance of diet in the growth and development of larvae of the blue crab,Callinectes sapidus rathbun,under laboratory conditions

The following protistan diets were tested on blue crab larvae: the algae Isochrisis galbana Parke, Monochrisis lutheri Droop, Dunaliella sp., and an unknown mixture; and the ciliated protozoans Euplotes vannus Muller and Parauronema virginianum(2/1) Thompson. None of these diets resulted in development past the first zoea stage, although some apparently were ingested and delayed mortality as compared to unfed controls.The rotifer Brachionus plicatilis Müller sustained good survival through early zoea development; however, rotifer-fed larvae did not metamorphose to the megalopa. Larvae of the polychaete Hydroides dianthus (Verrill) sustained crab larvae throughout zoea development, resulting in 17% survival to metamorphosis. The percentage mortality per stage was significantly lower in polychaete-fed larvae when compared with rotifer-fed larvae during zoea stages III, VI, and VII. Mean intermolt duration varied between diet treatments during the first three stages, but showed no differences during later zoea development. In tests on groups of late stage sibling larvae, Artemia salina L. nauplii gave development to metamorphosis, whereas rotifers did not.All the diets so far tested on blue crab larvae are classified according to their ability to sustain development. It is demonstrated that the two diets which allow completed development, Hydroides dianthus larvae and Artemia salina nauplii, contain 2–3 times as much lipid per dry weight as do rotifers. A metabolic requirement for lipid late in development may be indicated. Invertebrate larvae derived from yolky telolecithal and centrolecithal eggs may be an important dietary component for brachyuran larvae.     

Effects of the parasitization of a braconid, Apanteles, on the blood of its host, Pieris

Parasitization of a braconid wasp, Apanteles glomeratus, of larvae of a common cabbage butterfly, Pieris rapae crucivora, caused changes in differential haemocyte count (DHC), total haemocyte count (THC), and encapsulative capacity against dead eggs of Apanteles in the fourth and fifth instar host larvae.However, no correlation could be found between the number of Apanteles eggs deposited and THC of the middle fourth instar host larvae or between the number of parasitoid larvae and specific gravity of the haemolymph from the late fifth instar host larvae.From the changes in DHC and in THC of both non-parasitized and parasitized Pieris larvae, an increase in the number of plasmatocytes of non-parasitized Pieris larvae in the early fourth instar period was supposed to be due to transformation of prohaemocytes into plasmatocytes, and a low population of plasmatocytes of parasitized larvae in the comparable period was assumed to be due to a suppression of transformation of prohaemocytes by some factor released from the parasitoid eggs.Failure of the parasitized fourth instar Pieris larvae to encapsulate injected dead eggs of Apanteles indicated that the parasitoid embryos were, in some way, actively inhibiting the encapsulation reactions of the host.The increase in THC of the parasitized fifth instar larvae could not be ascribed to a decrease in the volume of host haemolymph. Rather it could be interpreted by a suppression of adhesive capacity of haemocytes in the host haemocoel to tissue surfaces.Reduced encapsulative capacity of the parasitized fifth instar larvae might be attributed either to a depression of the adhesive activity of plasmatocytes resulting from a depletion of energy source for haemocytes in the host haemolymph by parasitization, or from an active suppression of adhesiveness of the plasmatocytes by secretions from ‘giant cells’ (teratocytes) originated from the parasitoid.     

Niches and size relationships in Coleoptera associated with Cardueae host plants: adaptations to resource gradients

Summary The ecological meaning of size relationships within guilds is still a matter of debate. We analyzed the niches and size relationships in Coleoptera associated with Cardueae host plants. Species were grouped into guilds using distributional data, host records and feeding strategies: a) The species of the genus Larinus are inhabitants of flower heads within the Cynaroideae. Two types of Larinus species were distinguished: one type attacks immature flower heads, the other exploits the floer heads in a more advanced stage. The females of the first group have elongated rostres adapted to piercing through the bracts of closed flower heads, the other group possesses blunt, short rostres. For an oligophagous group of four Larinus species we are able to show that the distribution of average female rostre length is non-random. b) In southern France four stem boring species of the genera Agapanthia and Lixus coexist within the same hosts. The frequency distributions of body length from these species are clearly overdispersed. c) Coexisting species of the folivorous genus Cassida show no differences in body sizes. We conclude that morphometric differences within the investigated guild of endophytic species (Larinus and Agapanthia/Lixus) evolved in response to size of the used plant structures and the size of potentially competing species, a pattern not evident in ectophytic species. We suggest that these differences are part of a general pattern as the evolution of herbivorous guild may strongly depend on the way how the host resource is exploited (endophagy vs ectophagy). So current differences in statements on the organization of herbivore communities could perhaps be reconciled.     

Streptococcus faecalis,Bacillus alvei, and sacbrood virus in European foulbrood of the honey bee

Contrary to reports from elsewhere, Streptococcus faecalis or Bacillus alvei did not cause European foulbrood in bee larvae also inoculated with sacbrood virus. The larvae died of sacbrood, by which time S. faecalis had mostly disappeared, although B. alvei multiplied saprophytically, as in European foulbrood, in some of the remains. Larvae that died of sacbrood already contained much sacbrood virus before they were sealed in their cells, when they appeared unaffected by the virus, but when they are most likely to die of European foulbrood, which is caused by Streptococcus pluton, often accompanied by secondary invaders, such as S. faecalis. Therefore, larvae killed by European foulbrood can be expected sometimes to contain much sacbrood virus, particularly as this virus is common.     

Predation by a carnivorous marine copepod,Euchaeta norvegica Boeck,on eggs and larvae of the North Atlantic cod Gadus morhua L.

The predatory behavior of a carnivorous marine copepod, Euchaeta norvegica Boeck, feeding on eggs and larvae of the North Atlantic cod Gadus morhua L. was examined. In the laboratory, adult females of Euchaeta norvegica did not feed on eggs. Predation rates on yolk-sac larvae and starved post-yolk-sac larvae did not vary significantly with age up to 14 days old because of little change in size or activity of the larvae. This differs from E. elongata Esterly, a temperate congener, which selectively feeds on middle yolk-sac-stage larvae of the Pacific hake Merluccius productus Ayres. The subarctic congener Euchaeta norvegica appeared to detect tailbeats of the cod larvae. The functional response was measured for E. norvegica feeding on 2–4-day-old yolk-sac larvae. Maximum ingestion was achieved at 5 larvae · 1⁻¹ with a rate of 6.3 ± 1.2 larvae·copepod⁻¹·day⁻¹ or 10.5% of its body weight. Estimates of short-term feeding rates, determined from gut-evacuation curves, indicate that E. norvegica, when preying on cod larvae only, must feed for at least 4 h to achieve this maximum ingestion rate. Presence of copepods as alternative prey for E. norvegica depresses its predation rate on cod, although the ingestion of cod greatly supplements the ration consumed. Copepods fed cod larvae form black melanin-pigmented fecal pellets in which larval cod otoliths have been found. Approximately 0.5 larva was required to form one fecal pellet. The last three developmental stages of the predatory copepod were able to ingest larvae and form dark-pigmented fecal pellets. The feeding of this carnivorous marine copepod may contribute to the mortality noted in the larval stages of cod because E. norvegica is numerous in the center of the cod-spawning area of Skrova in the Lofoten Islands, northern Norway.     

Beziehungen zwischen Stoffwechselrate,Q10, Resistenz,Toleranz-bereich,Eury- und Stenothermie

During the development of larvae of Callitroga macellaria the rate of metabolism and the resistance against heat and low oxygen pressure was examined. The high rate of metabolism of very young larvae is correlated with low resistance, and the low rate of metabolism of old larvae is correlated with high resistance.The Q₁₀ value for the oxygen consumption of Callitroga larvae during five different phases has been measured within a temperature range of 2 to 47°C so far as phase III (mature feeding larvae) is concerned. It is shown that the assumption that tolerance and resistance limits depend on oxidative phosphorylation is correct.     

Romanomermis culicivorax parasitism and the development, growth, and feeding rates of two mosquito species

The dry weight, development, and feeding rates of Culex pipiens and Toxorhynchites amboinensis larvae infected with the nematode, Romanomermis culicivorax, were measured and gross conversion efficiences were calculated. The weight of C. pipiens larvae infected at two different inoculum levels did not differ significantly from controls until day 6 postinfection (PI). Infected larvae of T. amboinensis were significantly lighter than controls at days 2, 4, and 6 PI. The rate of larval mosquito development was slowed after day 3 in parasitized individuals of both mosquito species. Infection significantly retarded the interval feeding rate of the filter-feeding C. pipiens throughout development. Infected T. amboinensis larvae consumed significantly fewer prey larvae of C. pipiens than controls. Calculation of gross conversion efficiency (GCE) showed that lightly infected C. pipiens larvae had an elevated GCE early in the infection but were less efficient relative to controls after 4 days PI. Lightly parasitized T. amboinensis had a lower total GCE than controls.     

Differential host growth regulation by the solitary endoparasitoid, Meteorus pulchricornis in two hosts of greatly differing mass

Solitary koinobiont endoparasitoids generally reduce the growth of their hosts by a significant amount compared with healthy larvae. Here, we compared the development and host usage strategies of the solitary koinobiont endoparasitoid, Meteorus pulchricornis, when developing in larvae of a large host species (Mythimna separata) and a much smaller host species (Plutella xylostella). Caterpillars of M. separata were parasitized as L2 and P. xylostella as L3, when they weighed approximately 2 mg. The growth of parasitized M. separata larvae was reduced by almost 95% compared with controls, whereas parasitized P. xylostella larvae grew some 30% larger than controls. Still, adult wasps emerging from M. separata larvae were almost twice as large as wasps emerging from P. xylostella larvae, had larger egg loads after 5 days and produced more progeny. Survival to eclosion was also higher on M. separata than on P. xylostella, although parasitoids developed significantly faster when developing on P. xylostella. Our results provide evidence that koinobionts are able to differentially regulate the growth of different host species. However, there are clearly also limitations in the ability of parasitoids to regulate phenotypic host traits when size differences between different host species are as extreme as demonstrated here.     

Interactions between a braconid,Microplitis croceipes,and a fungus,Nomuraea rileyi,in laboratory-reared bollworm larvae

The parasite Microplitis croceipes required 1.1 days longer at 26°C to complete development in Heliothis zea larvae than was required for the fungus Nomuraea rileyi to kill the host larvae and sporulate. Host larvae parasitized by M. croceipes or infected with N. rileyi failed to complete a fifth larval molt or pupate. Of the remaining healthy larvae, one-half completed six larval stadia before popation. Larvae parasitized by M. croceipes were predisposed to infection by N. rileyi, but the fungus inhibited development of M. croceipes if host larvae were infected with N. rileyi within 1 day after parasitization.     

Weevils Lixinae (Coleoptera,Curculionidae) as gall formers

Galls induced by six species of Lixinae weevils from Ukrainian steppes are described. The gall formation by Larinus species is doubtful. One gall may in some cases be jointly occupied by different weevil species. The adaptive significance of gall formation in Lixinae is discussed.     

A Pathogenic Bacterium,Enterococcus faecalis,to the Beet Armyworm,Spodoptera exigua

A bacterial disease was found in the beet armyworm, Spodoptera exigua (Hübner). Blackened body of the infected larvae was a typical symptom of the epizootic disease especially at the intersegmental areas. We isolated the bacteria from the hemolymph of the infected 5th instar larvae and identified the isolate as a gram-positive bacterium, Enterococcus faecalis. When the 4th instar larvae were injected with the bacteria, half lethal dose of the bacteria was estimated as 22,593 colony-forming units (cfu) per larva and half lethal time of the bacteria was estimated as 2 days at 10⁷ cfu injection and 6 days at 10⁸ cfu injection. The bacteria were strongly resistant to each 1,000 ppm of ampicillin, kanamycin, and streptomycin. They were, however, relatively susceptible to mixture (1,000 ppm) of different combinations of the three antibiotics.     

Larval photoresponses of the polyclad flatworm Maritigrella crozieri (Platyhelminthes,Polycladida) (Hyman)

Phototaxis by larvae of the flatworm Maritigrella crozieri was used to determine spectral sensitivity, the ontogeny of the phototactic pattern, and the lowest light intensity to induce a directional response (intensity threshold). Adult M. crozieri live in shallow water with the tunicate Ecteinascidia turbinata and have a planktonic larval phase lasting longer than 3 weeks. The primary spectral sensitivity maximum was at 500 nm, which is probably an adaptation to the spectrum available underwater at twilight. The phototactic threshold changed with age, as dark-adapted, 1-week-old larvae had a threshold (1.84×10¹⁷ photons m⁻² s⁻¹) an order of magnitude higher than that of 3-week-old larvae. Flatworm larvae are relatively insensitive to light as compared to other invertebrate larvae. Young larvae were positively phototactic at high light intensities and negative at low, a pattern typical of a predator avoidance shadow response. In contrast, older larvae were only positively phototactic, which would be useful for transport to shallow-water adult habitats.     

Faunal make-up, host range and infestation rate of weevils and tephritid flies associated with flower heads of the thistle Cirsium (Cardueae: Astaraceae) in Japan

From 1988 to 1998, we collected flower heads of 39 thistle taxa (35 taxa of Cirsium, one species each of Breea, Synurus, Saussurea and Arctium; Cardueae; Astaraceae) in Japan, mainly from Hokuriku and other parts of central Honshu, and kept them in the laboratory to breed weevils and tephritid flies, the core fauna. We report the faunal make‐up, host plants, geographic distribution and the attack levels of the insects. Results indicated that (i) three Larinus species (Curculionidae) and three species of tephritid flies (Tephritis, Urophora and Xyphosia) comprised the core fauna; (ii) two insect species belonging to the same taxonomic group (either Curculionidae (Larinus) or Tephritidae) tended to use different host plant species; (iii) two sympatric Larinus species (L. latissimus and L. meleagris) segregated the host plants seasonally in central Honshu (Cirsium blooming in spring and autumn, respectively); and (iv) two tephritid fly species, Xyphosia punctigera and Urophora sachalinensis, segregated geographically (the former on the Japan Sea side and the latter on the Pacific Ocean side). In comparison with their European counterparts, the weevils and tephritids of the Japanese Cirsium are characterized by a lower species richness and a lower degree of specialization in usage of the thistle flower heads, with gall‐formers being distinctly under‐represented, and callus tissue‐feeders being absent. This reflects the fact that Japanese thistles are so closely related that hybridization frequently occurs, and also that the thistles have had a short history of interaction with the insects since the thistles’ arrival in Japan.     

Präadaptation, Wirtskreiserweiterung and Parallel-Cladogenese in der Evolution von phytophagen Insekten1, 2

Preadaptation, host shifts and parallel cladogenesis in the evolution of phytophagous insects In this contribution we investigate the possibilities to apply concepts developed for the evolution of animal parasites to insect-plant systems. We compare host parasite systems in animals with plant-herbivore systems and list similarities and differences. The terms preadaptation, predisposition, expansion and contraction of host ranges, and parallel cladogenesis are discussed. We enumerate general preadaptations for the evolution of herbivory in insects and preadaptations for shifts between herbivory and entomophagy. Examples are given for expansions of host ranges based on phytochemical or structural characters of host plants. Cases of parallel cladogenesis in herbivoreparasitoid systems and plant-herbivore systems are compiled from the literature. An analysis of the insect fauna of the “thistles” (Cynaroideae) in the Palearctic and Nearctic demonstrates the importance of the evolutionary history of the plant taxa and of the existence of preadapted pools of herbivores for the evolution of guilds of specialized herbivores. The members of the Curculionid taxon Cleoninae provide examples for multiple colonizations and radiations of herbivores on the Cynaroideae. The taxonomic and biological relationships of the weevil genera Rhinocyllus, Bangasternus and Larinus which exploit the flower heads of Cynaroideae, can be interpreted as result of a basic parallel cladogenesis between herbivore and host. A gelelectrophoretic analysis of Larinus spp. supports this hypothesis.     

Interactions and effects of multiple biological control insects on diffuse and spotted knapweed in the Front Range of Colorado

Abundances and interactions among biological control insects and their effects on target invasive plants were monitored within the flower heads and roots of diffuse knapweed, Centaurea diffusa, and in spotted knapweed, Centaurea stoebe, along the Colorado Front Range. Flower weevils, (Larinus species) and root-feeders (Cyphocleonus achates and Sphenoptera jugoslavica) were released on knapweed that already supported biological control gall flies (Urophora species). At a single monitoring site, seed production by C. diffusa declined from 4400 seeds m⁻² in 1997 to zero seeds m⁻² on the monitoring sites in 2006, while the flowering stem density of C. diffusa declined from a peak of almost 30 stems m⁻² in 2000 to zero stems m⁻² in 2006. The average abundance of Urophora and Larinus in flower heads fluctuated independently during the 2001–2006 interval, while the relative abundance of C. achates and S. jugoslavica in roots exhibited a weak inverse relationship that appeared driven by climate effects. The relative abundance of insects on a population of C. stoebe was monitored for five years as Larinus species and C. achates became established on spotted knapweed that already supported Urophora species. Spotted knapweed seed production on our monitoring site declined from 4600 seeds m⁻² in 2003 to zero seeds m⁻² in 2006. Unlike C. diffusa, substantial numbers of rosettes of C. stoebe remained present. Larinus consumed almost all Urophora encountered in C. diffusa, and consumed about 40% of the Urophora in co-infested flower heads of C. stoebe (ca. 10–15% of the total Urophora population). No negative correlations between the relative densities of flower head and root-feeding insects were observed. The effects of these insects on target plants have produced results consistent with the ‘cumulative stress hypothesis’ for biological control of Centaurea species.