Impact of worker longevity and other endogenous factors on colony size in the fire ant, <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

Central to the survival and reproduction of social insect queens is the size of colonies at maturity. The influence of exogenous factors such as predation, food abundance, and seasonal changes in temperature on colony size are well studied. Less well studied are endogenous life-history factors such as a queen’s fertility and lifespan, duration of worker development from egg to adult and worker lifespan. Endogenous factors regulating the rate of colony growth and colony size were simulated using the fire ant, Solenopsis invicta. Assuming ideal environmental conditions of no predation, abundant food and uniform temperature, the simulation showed unequivocally that colony size is determined by two endogenous factors: a queen’s egg-laying rate (R _q) and worker longevity (L _w) (Colony size = R _q × L _w). Thus, we are left with an unanswered question: if worker longevity contributes directly to colony size, why is the lifespan of workers so short—in most cases, a small fraction of a queen’s lifespan?     

The Role of Resource Density on Energy Allocation in the Neotropical Termite <Emphasis Type="Italic">Nasutitermes</Emphasis> aff. <Emphasis Type="Italic">coxipoensis</Emphasis> (Termitidae: Nasutitermitinae)

Organisms acquire energy from environment and must allocate it among different life traits (growth, maintenance and reproduction). Social insects must manage the energy allocation to various levels such as colony growth and caste functions. Here, we addressed the question of whether resource density affects the energy allocation to the number of individuals and caste functions as well as nest’s growth rate in the Neotropical termite Nasutitermes aff. coxipoensis (Homgren) (Termitidae: Nasutitermitinae). In a manipulative field experiment, colonies of N. aff. coxipoensis, with known volume, were maintained in plots with three different resource’s density (0.32, 0.64 and 1.92 baits/m²) over 3 months. After this period, the number of individuals as well as the caste identity and nest volume were measured. Surprisingly, our results showed that colonies reared in the extremes of resource’s density (0.32 and 1.92 baits/m²) produced a higher number of individuals compared with colonies reared with intermediate resource density (0. 64 baits/m²). The mean number of workers increased linearly with resource density; however, the average number of immature was higher in colonies reared with 0.32 baits/m² compared with colonies reared with 0.64 and 1.92 baits/m². No significant differences of resource density were observed in the mean number of soldiers, worker/soldier ratio as well as in the nest’s growth rate. In conclusion, the resource’s density seems to play an important role in determining the investment of energy in the number of individuals and caste in N. aff. coxipoensis colonies.     

Independent hybrid populations of <Emphasis Type="Italic">Formica polyctena X</Emphasis><Emphasis Type="Italic">rufa</Emphasis> wood ants (Hymenoptera: Formicidae) abound under conditions of forest fragmentation

Combined genetic and morphological data indicate frequent hybridisation between the wood ants Formica polyctena Förster 1850 and F. rufa Linnaeus 1761 in Central Europe. The genetic and morphological traits give a concordant picture of hybridisation with a strong correlation between the genotypic admixture proportions at 19 microsatellite loci and the first vectors of a principal component analysis (P < 0.001) and of a 3-class discriminant analysis (P < 0.001) of 15 quantitative morphological characters. This integrative approach enabled a grouping into F. polyctena, the hybrid and rufa. Genetic differentiation between the hybrid and F. rufa is significantly larger than between the hybrid and polyctena, indicating gene flow mainly between the latter entities. A suggested gene flow bias towards F. polyctena agrees with differential queen acceptance and mating behaviour. Both genetic and phenotypic colony parameters indicate predominance of monogyny in F. rufa but of polygyny in polyctena and the hybrid. Hybrids are intermediate between the parental species in body size, diagnostic morphological characters, monogyny frequency, size of nest population, nest diameter and infestation rate with epizootic fungi. The three entities respond differently to woodland fragmentation. Hybrids are significantly more abundant in forests with a coherent area <300 ha than in woodland above this size. Regions with high hybrid frequency in Germany—the Eastern Oberlausitz (23%) and the Baltic Sea islands Darss, Hiddensee and Rügen (28%)—are characterised by a fragmented woodland structure whereas regions with low hybrid frequency—Brandenburg and the lower Erzgebirge (3.4%)—have clearly larger and more coherent forest systems. Data from other European countries indicate habitat fragmentation to be a facilitating factor but no essential precondition for interspecific hybridisation in these ants. Hybrids are hypothesised to have selective advantage in fragmented systems because of combining the main reproductive and dispersal strategies of the parental species.     

Host suitability of the Mediterranean flour moth for rearing <Emphasis Type="Italic">Meteorus pulchricornis</Emphasis> (Hymenoptera: Braconidae), a polyphagous endoparasitoid of pest lepidopteran larvae

We investigated the host suitability of the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) for a polyphagous koinobiont endoparasitoid Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae), a common natural enemy of various pest lepidopteran larvae. The estimated probability of adult wasp emergence was 80% or higher when eggs were laid in nearly fully grown larvae of E. kuehniella (fresh weight, >?20.0 mg). The body size of emerged adult wasps increased with the initial weight of the host larvae at oviposition. The fresh weight of adult wasps reared on E. kuehniella was approximately 60% of that when reared on a natural host Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), and the lifetime fecundity of wasps reared on E. kuehniella was approximately half of that when reared on S. litura. Ephestia kuehniella was shown to be a positive host candidate for the mass rearing of M. pulchricornis, but further investigation is needed to increase the body size of wasps for more practical use of this species as a biocontrol agent.     

Parasitoids and fungal pathogens of <Emphasis Type="Italic">Phyllonorycter issikii</Emphasis> (Kumata, 1963) from Bulgaria

The lime leaf miner, Phyllonorycter issikii, is a moth species native to East Asia, which recently invaded considerable part of Europe. A study on the natural enemies of this invasive species was conducted in Bulgaria. Tilia cordata leaves infested with the lime leaf miner were collected in 2015 and 2016 in two public parks in Sofia. A total of eleven eulophid parasitoids (Hymenoptera: Eulophidae) belonging to three subfamilies - Entedoninae, Eulophinae and Tetrastichinae, and one braconid species (Hymenoptera: Braconidae) were recorded. In addition, one unidentified ichneumonid species was reared. Minotetrastichus platanellus was the most abundant species in the samples comprising 76.88% of the parasitoids reared from collected immature and pupal stages of Ph. issikii. It is followed by Sympiesis gordius (6.53%) and S. sericeicornis (6.03%). Three new host-parasitoid associations were established. The entomopathogenic fungi Beuveria bassiana and Metarhizium anisopliae (Hypocreales) were isolated for the first time from cadavers of Ph. issikii larvae and pupae. Based on the presented observation we hypothesized that the lime leaf miner can produce three generations in Bulgaria.     

First come,first served: the first-emerging queen monopolizes reproduction in the ant <Emphasis Type="Italic">Cardiocondyla</Emphasis> “<Emphasis Type="Italic">argyrotricha</Emphasis>”

While colonies of most tropical species of the ant genus Cardiocondyla regularly contain multiple egg-laying queens (polygyny), single-queening (monogyny) evolved convergently in a Palearctic clade of Cardiocondyla and in Southeast Asian C. “argyrotricha.” In the latter species, monogyny is probably an adaptation to patchily distributed but highly stable nest sites. In experimentally orphaned colonies of C. “argyrotricha,” the first emerging queen shed its wings, began to lay eggs, and stayed mostly on the brood pile. Queens that emerged later remained in the peripheral areas of the nest without dispersing but retained their wings even after mating in the nest. Aggressive interactions among queens and between workers and queens were occasionally observed, but it appears that the order of queen emergence determines which of them will become reproductive and inherit the nest. We conclude that young queens commonly compete for nest inheritance in some species of Cardiocondyla and that queen–queen antagonism does not necessarily involve lethal fighting.     

Reproductive Biology and Behavior of <Emphasis Type="Italic">Tranosema rostrale</Emphasis> (Hymenoptera: Ichneumonidae), a Parasitoid of Low-Density Spruce Budworm (Lepidoptera: Tortricidae) Populations

Tranosema rostrale (Brischke) (Hymenoptera: Ichneumonidae) is an important parasitoid of low-density spruce budworm Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) populations. To investigate the effectiveness of this parasitoid in attacking low-density spruce budworm populations, we conducted a detailed laboratory study on its reproductive biology and behavior including mating behavior, potential fecundity, longevity, host searching, and oviposition behavior. We found that the occurrence of mating increases with the number of males present in the cage but that it drastically decreases when females mated previously. Females may mate multiple times with different males in one breeding session and mating duration is significantly longer when a male mates the second time with the same female. Dissections of T. rostrale’s oviducts showed that it is a synovigenic species emerging with about 17 % of its lifetime egg load and develops most of its eggs in the first three days after emergence at 20 °C. Sugar, but not pollen, significantly increased the insect’s longevity compared to water. Spruce budworm larvae, silk from larvae and damaged balsam fir foliage triggered probing in T. rostrale females significantly more often than larval feces. The sequence of the parasitoid’s behaviors leading to successful attack is described as antennation, probing, insertion of the ovipositor, oviposition, and subsequent disinterest or resuming of the sequence. Defense mechanisms of the host larva such as vigorous movements, biting, and/or regurgitation and behavioral countermeasures by T. rostrale are described in detail.     

Effect of host species,host nest density and nest size on the occurrence of the shining guest ant <Emphasis Type="Italic">Formicoxenus nitidulus</Emphasis> (Hymenoptera: Formicidae)

Understanding habitat requirements of species is important in conservation. As an obligate ant nest associate, the survival of the globally vulnerable shining guest ant, Formicoxenus nitidulus, is strictly tied to that of its hosts (mound building Formica ants). We investigated how host species, nest density, inter-nest distance and nest mound size relate to the occurrence of F. nitidulus. In total, 166 red wood ant nests were surveyed in SW Finland (120 Formica polyctena, 25 F. rufa, 14 F. aquilonia, 5 F. pratensis, and 2 F. lugubris). Overall, F. nitidulus was found in 60% of the nests. For the actual analysis, only F. polyctena and F. rufa nests were included due to the small number of other nests. F. nitidulus was more likely to be found among F. polyctena than F. rufa. Also, while inter-nest distance was not important, a high nest density, commonly found in polydomous (multi-nest) wood ant colonies, was beneficial for F. nitidulus. The guest ant was also more likely to be found in large host nests than small nests. Thus, our results show that the best habitat for the guest ant is a dense population of host nest mounds with a high proportion of large mounds. Conservation efforts should be directed at keeping the quality of the red wood ant habitats high to preserve their current populations and to increase colonization. This will not only benefit the guest ant, but also a plethora of other species, and help in maintaining the biodiversity of forests.     

To the knowledge of the <Emphasis Type="Italic">Sphecodes hyalinatus</Emphasis> Hagens species-group (Hymenoptera,Halictidae)

Five species of the hyalinatus species-group of the genus Sphecodes Latreille 1804 (Hymenoptera, Halictidae) are reviewed. Sphecodes maruyamanus Tsuneki and S. murotai Tsuneki are found in Russia for the first time, and S. hyalinatus Hagens is newly recorded from the Kuril Islands (Kunashir). Illustrated keys to males and females of all the species of the S. hyalinatus species-group are provided. An updated checklist of 37 species of the genus Sphecodes is given.     

<Emphasis Type="Italic">Hsp70</Emphasis> genes of the <Emphasis Type="Italic">Megaphragma amalphitanum</Emphasis> (Hymenoptera: Trichogrammatidae) parasitic wasp

Miniaturization is an evolutionary process that is widely represented in both invertebrates and vertebrates. Miniaturization frequently affects not only the size of the organism and its constituent cells, but also changes the genome structure and functioning. The structure of the main heat shock genes (hsp70 and hsp83) was studied in one of the smallest insects, the Megaphragma amalphitanum (Hymenoptera: Trichogrammatidae) parasitic wasp, which is comparable in size with unicellular organisms. An analysis of the sequenced genome has detected six genes that relate to the hsp70 family, some of which are apparently induced upon heat shock. Both induced and constitutively expressed hsp70 genes contain a large number of introns, which is not typical for the genes of this family. Moreover, none of the found genes form clusters, and they are all very heterogeneous (individual copies are only 75–85% identical), which indicates the absence of gene conversion, which provides the identity of genes of this family in Drosophila and other organisms. Two hsp83 genes, one of which contains an intron, have also been found in the M. amalphitanum genome.     

Caste-Specific Expression of Na<Superscript>+</Superscript>/K<Superscript>+</Superscript>-ATPase in the Asian Weaver Ant, <Emphasis Type="Italic">Oecophylla smaragdina</Emphasis> (Fabricius, 1775)

Social insect colonies adopt different levels of survival strategies and exhibit well-defined reproductive division of labour. Oecophylla smaragdina (Fabricius, 1775) has physiological and behavioral adaptations that enable them to forage at extreme environmental conditions and are lethal to most other insects. Ion homeostasis is the key process in an organism’s survival mechanism. Among ion pumps, the ATP-dependent sodium–potassium ion pump is essential for maintaining the Na⁺ and K⁺ ionic balance and is well known as the primary consumer of energy. Oecophylla smaragdina plays pivotal role as a model among social insects for understanding ion homeostasis at the organization level of the castes. We have evaluated the expression and activity of Na⁺/K⁺-ATPase among various castes of O. smaragdina (worker subcastes, queen and male). Real-time PCR and immunoblotting analyses revealed the differential expression of Na⁺/K⁺-ATPase in the castes. Significantly higher expression of Na⁺/K⁺-ATPase mRNA and protein were observed in the minor workers, queen, major workers and males respectively. These results suggest that in the weaver ant colony, the castes might have variously adapted and evolved with a well-developed ion transport mechanism which allows them to perform allocated tasks within the nest and could be a key to their adaptive benefits towards division of labour.     

Reproductive Biology of <Emphasis Type="Italic">Leptocybe invasa</Emphasis> Fisher &amp; La Salle (Hymenoptera: Eulophidae)

Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is an invasive pest in Eucalyptus plantations around the world. The successful colonization of L. invasa is possibly related to its reproductive biology. The objective of this study was to examine the reproductive biology of L. invasa. In Guangxi Province, the sex ratio (proportion of female, 0.99) of L. invasa was female-dominant throughout the year based on natural and artificial infestation. This result was similar to the ratios observed for other geographic populations in China, including those in Fujian (0.99), Guangdong (0.98), Hainan (0.95), Jiangxi (0.96), and Sichuan (0.99). The offspring sex ratio favored females. A large number of females emerged from the galls produced by females, with few males found. Galls on the petioles and midribs of Eucalyptus plants could be caused by newly emerged females with mature eggs. The lengths of the ovariole, spermatheca, common oviduct, and reproductive glands did not differ among L. invasa females, but their lateral oviducts showed differences from 0 to 42 h after emergence, indicating that this insect is proovigenic. These results could explain why L. invasa populations can rapidly increase in invaded areas.     

Nest-building in ants <Emphasis Type="Italic">Formica exsecta</Emphasis> (Hymenoptera,Formicidae)

Representatives of the subgenus Coptoformica build composite aboveground nests in much the same manner as red wood ants do. However, despite the superficial similarity, Coptoformica nests show a number of substantial differences that impact on the way in which ants use the nest. The aboveground part of a Formica (Coptoformica) exsecta nest consists of the temporary layer, the outer crust layer, the mound, and the intermediate layer. The material of all the layers includes soil and fragments of plants (picked up or excised), the relative proportion of the two components differing among the layers. The thick, soil-rich crust layer acts as armature and allows a variety of anthill shapes. The intermediate layer and the upper part of the mound harbor quite a few large chambers. Building material is often transferred from nest to nest. On the whole, F. exsecta nests are plastic and movable, which facilitates the activity of these ants in ecotone biotopes.     

The Psilostomidae Looss, 1900 (<Emphasis Type="Italic">sensu stricto</Emphasis>) (Digenea: Echinostomatoidea): description of three new genera and a key to the genera of the family

Three new psilostomid genera, Byrdtrema n. g., Longisaccus n. g. and Macracetabulum n. g., each with a single species, are described from ducks, Aix sponsa (L.) and Bucephala albeola (L.) in North America. Byrdtrema n. g. and Macracetabulum n. g. possess a bipartite seminal vesicle and share this character with four psilostomid genera, Grysoma Byrd, Bogitsh & Maples, 1961, Neopsilotrema Kudlai, Pulis, Kostadinova & Tkach, 2016, Psilostomum Looss, 1899 and Psilotornus Byrd & Prestwood, 1969. Byrdtrema n. g. differs from Macracetabulum n. g. in the shape of the body (elongate vs elongate-oval); the position of the ventral sucker (in first third of body vs just pre-equatorial); the shorter forebody; as well as in the smaller size of the eggs in relation to body length. Both new genera differ from (i) Grysoma by the nature of the vitellarium (large, compact follicles with small vitelline cells vs weakly defined follicles with large vitelline cells, respectively) and the smaller size of the eggs in relation to body length; (ii) Psilostomum in the posterior extend of the cirrus-sac in relation to ventral sucker (slightly posterior vs more posterior), the location of the genital pore (at the level of oesophagus vs just postbifurcal), the shorter length of uterine and longer post-testicular fields in relation to body length, and the anterior limits of vitellarium (at the level of ventral sucker vs posterior to ventral sucker); (iii) Psilotornus by the presence of a muscular pharynx (vs absent or rudimentary) and the location of the cirrus-sac (antero-dorsal to ventral sucker or more posterior vs entirely anterior to ventral sucker) and ovary (in hindbody vs in forebody). Byrdtrema n. g. differs from Neopsilotrema in the shape of the body (elongate vs subspherical to elongate-oval) and ventral sucker (elongate-oval vs subspherical to transversely oval), the shorter forebody and smaller eggs in relation to body length. Macracetabulum n. g. differs from Neopsilotrema by the shape of the ventral sucker (elongate-oval vs subspherical to transversely oval), the anterior limits of vitellarium (level of middle of ventral sucker vs level of intestinal bifurcation or anterior testis); and the slightly smaller size of eggs in relation to body length. Among the psilostomid genera, Longisaccus n. g. shows close affinities to Psilochasmus Lühe, 1909 in the presence of the long cirrus-sac and tubular internal seminal vesicle but can be clearly distinguished from the latter by the absence of the retractile tail-like process. In combination with molecular data, the above differences justify the recognition of three new genera. A key to the genera of the Psilostomidae is provided.     

Maternal care,larviparous and oviparous reproduction of <Emphasis Type="Italic">Hypoaspis larvicolus</Emphasis> (Acari: Laelapidae) feeding on astigmatid mites

Hypoaspis larvicolus (Acari: Laelapidae) (first report from Turkey) occurred together with Sancassania polyphyllae (Acari: Acaridae) on the larvae of the scarab beetle, Polyphylla fullo (Coleoptera: Scarabaeidae), that were feeding on the roots of strawberry in Aydin, Turkey. Laboratory studies were conducted to (1) observe whether H. larvicolus feeds and completes its life cycle on the various stages of S. polyphyllae or other astigmatid mites, such as Acarus siro, Carpoglyphus lactis and Tyrophagus putrescentiae (Acaridae), and to determine its population growth when feeding on these prey, and (2) to determine development periods, longevity and fecundity of H. larvicolus feeding on C. lactis. Hypoaspis larvicolus females did not feed on S. polyphyllae, but fed, developed and reproduced when A. siro, C. lactis or T. putrescentiae were provided as prey. Hypoaspis larvicolus is larviparous as well as oviparous. The female lays eggs or gives birth to larvae. If a female gives birth to a larva, it is attached under the female’s venter for 1–2 days, a phenomenon recorded for the first time in Hypoaspis; in fact, for the first time in mites. The results of the population growth experiments revealed that H. larvicolus feeding on C. lactis produced the highest number of eggs, juveniles and adults. The developmental periods of H. larvicolus feeding on C. lactis at life-cycle path I (larva to adult) and II (egg to adult) were 12.2?±?0.3 and 15.6?±?0.6 days (females) and 19.5?±?0.2 and 20.9?±?0.4 days (males), respectively. Longevity of females versus males of H. larvicolus was 120.6?±?7.2 versus 91.6?±?13.1 days (life cycle I) and 110.0?±?27.7 versus 118.3?±?10.9 days (life cycle II), respectively.     

Host preferences and biotic potential of <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> and <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Hemiptera: Aleyrodidae) in tomato and pepper

Whiteflies Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are important pests in pepper (Capsicum annuum L.) and tomato (Solanum lycopersicum L.) crops in many countries. Contrary to what is observed for all other countries, in Uruguay, B. tabaci is mainly found on pepper and rarely on tomato, while T. vaporariorum is exclusively found on tomato. This study tested the oviposition preferences and biotic potential of these two whiteflies reared on both host plants. The developmental time, survival rates, longevity, fecundity and main population parameters were characterized. Both whitefly species showed different preference patterns regarding their host plants. T. vaporariorum preferred tomato instead of pepper to oviposit. Their developmental time is longer on pepper. B. tabaci preferred pepper, but the difference from tomato was not very strong. Pepper affects the biotic expression of T. vaporariorum negatively, while B. tabaci is able to develop equally on both host plants. These results show that the distribution differences of both whiteflies observed on both host plants could have a biological basis.     

Host Foraging Behavior of <Emphasis Type="Italic">Dastarcus helophoroides</Emphasis> (Coleoptera: Bothrideridae) Adults,a Coleopteran Parasitoid of <Emphasis Type="Italic">Monochamus alternatus</Emphasis> (Coleoptera: Cerambycidae)

Dastarcus helophoroides adults, a coleopteran parasitoid of Monochamus alternatus, were reared in the laboratory. The objectives of this paper are to investigate the host foraging behavior of D. helophoroides, and the evidence for learning in such behaviors. Choice and no-choice experiments were carried out. The choice experiments show that the number of D. helophoroides adults choosing the Pinus massoniana log infested with M. alternatus larvae was significantly higher than that choosing the blank (a flavorless simulative log made of brown kraftpaper), and the number of D. helophoroides adults choosing the uninfested P. massoniana log was also significantly higher than that choosing the blank. The no-choice experiment shows no significant difference between the number of D. helophoroides adults that chose the infested log and that chose the uninfested log, despite previous experience with uninfested log, infested log, or neither of them. No evidence of learning in host foraging behavior in D. helophoroides adults was found. The results indicate that the volatile chemicals emitted by uninfested P. massoniana logs and infested logs with M. alternatus larvae are equally attractive to D. helophoroides.     

Effect of gut bacteria on fitness of the Chinese citrus fly, <Emphasis Type="Italic">Bactrocera minax</Emphasis> (Diptera: Tephritidae)

A likely symbiotic association between tephritid fruit flies and gut bacteria has been recognized since the beginning of the last century. However, direct evidence for a link between gut bacteria and fruit fly fitness is still limited or absent for many species. Similar to other tephritids, the gut of Bactrocera minax (Enderlein) (Diptera: Tephritidae) is known to contain bacteria throughout the life stage, but what, if any, impact these bacteria have on B. minax fitness is entirely unknown. In order to elucidate the effects of bacteria on the fitness of B. minax, resident bacteria were isolated from the adult gut using culture-dependent techniques. Adult fly diets were subsequently supplemented with three bacterial isolates (Klebsiella pneumonia, Citrobacter braakii and Pantoea dispersa), or bacteria were removed from flies by antibiotics treatment: untreated adults provided a control. Adult fitness parameters (male and female longevity, female fecundity, male copulation number) were measured for the two treatments and one control group. Results were complex depending on the fitness parameter measured and the bacterial species. Compared to the controls, antibiotic treated B. minax had significantly decreased fecundity, but male and female longevity was increased. When flies were fed diets supplemented with any of the three bacterial isolates, female fecundity was significantly enhanced. However, only Citrobacter braakii significantly increased male mating frequency than control males. The results show that gut bacteria directly influence fitness of B. minax, but impacts are dependent on the bacterial species and the fitness parameters measured.