Spider Egg Research Articles

RESOURCE PARTITIONING OF SPIDER HOSTS (ARACHNIDA, ARANEAE) BY TWO MANTISPID SPECIES (NEUROPTERA, MANTISPIDAE) IN AN ILLINOIS WOODLAND

Two spider-boarding mantispids, Mantispa uhleri Banks 1943 and Climaciella brunnea (Say 1824), were found to be partitioning available spider egg resources in an Illinois woods based on vertical stratification. Mantispa uhleri was found to be phoretic on the philodromid Philodromus vulgaris (Hentz 1847), the salticid Metacyrba undata (De Geer 1867) and the anyphaenid Aysha gracilis (Hentz 1847) at levels of 75%, 26%, and 27% respectively. All of these spiders were collected from areas above the forest floor. In contrast, C. brunnea was collected from 19% of leaf litter-inhabiting lycosids of the genus Schizocosa. There was no host range overlap within the woods, but in a grassy field without appreciable stratification of vegetation adjacent to the woods, both M. uhleri and C. brunnea were found aboard the lycosid Rabidosa punctulata (Walckenaer 1837) at levels of 2% and 7% respectively. A single larva of Mantispa pulchella (Banks 1912) associated with an anyphaenid from the woodland sample was also collected in this study. Mantispids are far more common than has been previously supposed and are likely an important factor in spider population dynamics and the evolution of spider behavior.

Modular Habitat Refugia Enhance Generalist Predators and Lower Plant Damage in Soybeans

Promoting generalist predators in agriculture via habitat manipulation has gained much interest in biocontrol research. Straw shelters have been used by Chinese farmers for >2,000 yr to provide temporary spider refugia during cyclic farming disturbances. This method, however, has not been systematically investigated on larger scales in western-style agriculture. Our preliminary observations indicated a significant decrease in the abundance of spiders (76%) and their egg sacs (75%), after conventional tillage of soybeans [Glycine max (L.) Merr.]. We hypothesized that providing alternative habitats in tilled fields could conserve predatory assemblages following this major disturbance. We used modular habitat refugia constructed of chicken wire loosely filled with bedding straw to provide temporary habitats for epigeic predators in a soybean field. Refugia held 5–36 times the spider density compared with open field, and the production of spider egg sacs was enhanced 18–87 times. Almost 60% more spider species were found in refugia than in open field. Abundance of harvestmen, carabids, and staphylinid beetles also significantly increased in habitat refugia. Increased habitat cover and provision of alternative prey in habitat refugia may have caused this dramatic predator increase. Soybean seedlings grown within 1 m of habitat refugia suffered 33% less insect damage compared with plants at control locations. Decrease in seedling damage, however, did not significantly increase soybean seed production. Applications of discrete habitat refugia may provide an alternative to habitat manipulation techniques to conserve and augment arthropod predators in agroecosystems.

Modular Habitat Refugia Enhance Generalist Predators and Lower Plant Damage in Soybeans

Promoting generalist predators in agriculture via habitat manipulation has gained much interest in biocontrol research. Straw shelters have been used by Chinese farmers for >2,000 yr to provide temporary spider refugia during cyclic farming disturbances. This method, however, has not been systematically investigated on larger scales in western-style agriculture. Our preliminary observations indicated a significant decrease in the abundance of spiders (76%) and their egg sacs (75%), after conventional tillage of soybeans [Glycine max (L.) Merr.]. We hypothesized that providing alternative habitats in tilled fields could conserve predatory assemblages following this major disturbance. We used modular habitat refugia constructed of chicken wire loosely filled with bedding straw to provide temporary habitats for epigeic predators in a soybean field. Refugia held 5–36 times the spider density compared with open field, and the production of spider egg sacs was enhanced 18–87 times. Almost 60% more spider species were found in refugia than in open field. Abundance of harvestmen, carabids, and staphylinid beetles also significantly increased in habitat refugia. Increased habitat cover and provision of alternative prey in habitat refugia may have caused this dramatic predator increase. Soybean seedlings grown within 1 m of habitat refugia suffered 33% less insect damage compared with plants at control locations. Decrease in seedling damage, however, did not significantly increase soybean seed production. Applications of discrete habitat refugia may provide an alternative to habitat manipulation techniques to conserve and augment arthropod predators in agroecosystems.

A troublesome sibling species complex of scuttle flies (Diptera: Phoridae) revisited

The complex of species resembling Megaselia pulicaria (Fallén) has proved to be one of the most troublesome challenges to attempts to resolve the recognition of species within the huge genus Megaselia Rondani. The new data presented allow more confident recognition of species and reveal that most published records represent misidentifications. The penis complex is discussed and its use in species identification demonstrated. All specimens currently assigned to M. pulicaria, other than the lectotype, are consequently reassigned to other species. These include the reinstatement of M. angusta (Wood) and its newly designated subspecies M. angusta angustina Schmitz, M. eupygis Schmitz, M. longifurca (Lundbeck) and M. monochaeta (Strobl) as valid species, and the recognition of M. buchsi sp. nov. from Germany, M. iberiensis sp. nov. from Spain, M. martensi sp. nov. from Nepal, M. nectergata sp. nov. from Britain, M. oviaraneae sp. nov. from Britain, and M. rotundapicis sp. nov. from Scotland. Five synonyms are proposed. The hitherto unknown male of M. petraea Schmitz is described. It and M. longifurca are reported from Britain and the latter from the Nearctic Region also. Natural history information is summarized for each species. In particular, it is reported that the species whose larvae prey upon spider eggs are M. angusta, M. longifurca and M. oviaraneae.

From Specialization in Spider Egg Predation to an Original Nesting Mode in a "Primitive" Ant: A New Kind of Lestobiosis

Mature colonies of Discothyrea oculata were observed nesting in cribellatid spider oothecas where they found both shelter and food although these oothecas, installed in preexisting cavities, were protected with crimped silk. Workers of colonies bred in test tubes during laboratory experiments recuperated the silk from spider oothecas introduced into their foraging area, using their mandibles and forelegs, to operculate and line the test tubes. Also, colonies left the test tubes to shelter in the cribellatid spider oothecas. The term "arachnolesty" is proposed for this new kind of lestobiosis.

How a ponerine ant acquired the most evolved mode of colony foundation

Founding queens of the ponerine ant Discothyrea oculata always install themselves in spider nests where both shelter and ample food permit their entire first brood to develop, while other Ponerinae repeatedly forage for prey. This evolved mode of founding colonies is nevertheless different from that of subfamilies with claustral colony founding (first generation nanitic workers developing from larvae fed from the queen's reserves) as the first workers, developing from larvae fed on spider eggs, are of a similar size as those of mature colonies.

A linear model for description of the relationship between the lower threshold temperature and thermal constant in spiders (Araneae: Arachnida)

The thermal constant ( K) and the threshold temperature ( T 0) for development of eggs were estimated by using linear regression for 16 species (17 populations) of spiders. T 0 ranged between 4.2 and 16.8°C, K between 64.1 and 217.4 day-degrees ( dd). When T 0 was plotted against K, the data were scattered along a single regression line ( T 0 = 18.05−0.063 K) which predicted a 0.63°C decrease in T 0 per 10 dd increase in K. The present paper is the first report, in spiders, of a linear relationship between T 0 and K at interspecific level. The typical development time ( VDT) and the extent of its deceleration by low temperature ( DD) varied between species. DD increased with increasing VDT, but the relative effect of low temperature on development time ( DD VDT ratio) varied independently of VDT, reflecting thermal adaptations consistent with the life history of the species. There is evidence that the DD VDT ratio for eggs of spiders is smaller than that of insects.

First Observation of Egg Sac Predation of the Mantisfly, Mantispa interrupta (Neuroptera, Mantispidae) upon the Wolf Spider, Gladicosa gulosa (Araneae, Lycosidae)

Although adult mantisflies of the subfamily Mantispinae prey upon a variety of insect species, during the larval stage they are obligate predators of spider eggs (Redborg and MacLeod, 1985; Hoffman and Brushwein, 1989). The mobile, campodeiform larvae gain entrance to spider egg sacs by either directly burrowing into an egg sac, or by boarding a female spider and entering the egg sac as it is being produced. Some species (Mantispa viridis Walker) are obligate egg sac penetrators, whereas others, such as Mantispa sayi Banks, can utilize both methods (Redborg and MacLeod, 1985). Inside the egg sac, the larva passes through three instars and transforms into a pupa. The pharate adult then emerges from both the pupal case and the spider egg sac. Soon after emergence it sheds one more time, transforming into a fully functional adult mantisfly (Hoffman and Brushwein, 1990). On 8 March 1997, a female Gladicosa gulosa (Walckenaer) (Araneae, Lycosidae) was captured in a mesic woodland on the Red Buffalo Ranch, in Chautauqua County, Kansas. The spider was maintained at room temperature in a laboratory of the Department of Entomology, University of Kansas. An egg sac was produced on 15 March, and a pharate adult Mantispa interrupta Say emerged at sunset on 17 April. Within an hour, it shed to the adult stage. No live spiderlings occurred in the egg sac after the mantispid's emergence. Instead of characteristically carrying the egg sac attached to her spinnerets, the female wolf spider ignored her egg sac for approximately one week prior to the mantispid's emergence. The emergence of the mantispid at sunset is consistent with Brushwein's observations of the emergence of M. interrupta between 1900 and 2200 hours EST (Brushwein, Culin, and Hoffman, 1995). Spider host associations for Mantispa interrupta have been summarized by Hoffman and Brushwein (1990). A laboratory study by Viets (1941) first demonstrated M. interrupta larvae boarding a female lycosid and the subsequent emergence of an adult mantisfly from the spider's egg sac. Pharate adults of M. interrupta have been recorded emerging from egg sacs of: Gnaphosa muscorum (C. L. Koch) (Gnaphosidae) (Kaston, 1940), Rabidosa rabida (Walckenaer) [reported as Lycosa rabida Walckenaer] (Lycosidae) (Rice, 1985), Eris militaris (Hentz) [reported as Philaeus militaris (Hentz)]

Biology of the Mantispidae.

Members of the Neuropteran family Mantispidae, subfamily Mantispinae, are predators in the egg sacs of spiders, draining egg contents through a piercing/sucking tube formed by modified mandibles and maxillae. First-instar mantispids use two strategies to locate spider eggs: Larvae may burrow directly through the silk of egg sacs they find, or they may board and be carried by female spiders prior to sac production, entering the sac as it is being constructed. Mantispids that board spiders usually adopt positions on or near the pedicel; some species may enter the spider's book lungs. Larvae maintain themselves aboard spiders by feeding on spider blood. Transfers of larvae from spider to spider are possible during spider mating or cannibalism. All of the major groups of hunting spiders are attacked by spider-boarding mantispids; the egg sacs of web-building species are also entered by egg-sac penetrators.

Coras Medicinalis (Araneae, Amaurobiidae), a New Host of the Mantisfly, Mantispa viridis (Neuroptera, Mantispidae)

member of the family Amaurobiidae. Mantisfly larvae enter spider egg sacs by either boarding the adult female spider and entering the sac as it is being produced, or by locating and directly penetrating the egg sac after it has been laid. M. viridis is an obligate egg sac penetrator (Redborg and MacLeod 1985). Therefore, the developing mantispid was inside one of the C. medicinalis egg sacs when it was collected and completed development in captivity. M. viridis has been associated with 29 spider species belonging to fifteen different families (Brushwein, Hoffman, and Culin, 1992). Some of these spider hosts include: Gladicosa pulchra (Keyserling) (Lycosidae) (Roble, 1986), Argiope aurantia Lucas (Argiopidae) (Tolbert, 1976), Achaearanea tepidariorum (C. L. Koch) (Theridiidae) (Valerio, 1971), Peucetia viridans (Hentz) (Fink, 1987), Agelenopsis sp. (Agelenidae) (Parfin 1958), and Cupiennius salei (Keyserling) (Ctenidae) (Milliron, 1940). This note extends the host list to the Amaurobiidae with the inclusion of Coras medicinalis.

New species of baeine parasitoids of spider eggs (Hymenoptera: Scelionidae) from Western Australia.

Six species of scelionid wasps from Western Australia belonging to the tribe Baeini, a group known only to be parasitic on spider eggs, are described as new: Mirobaeoides barbarae, M. manjimupensis, Ceratobaeus mainae, C. clavisegmentus, Hickma/lella walpolensis and H. noyesi. These species extend the morphological limits of their respective genera, and in the case of Mirobaeoides, enough to warrant its redescription. Psyllobaeus Austin (type species P. pecki Austin) known only from Lord Howe Island is synonymised with Mirobaeoides. Additional diagnostic notes are provided for Ceratobaeus Ashmead and Hickmanella Austin, along with comments on the relationships of the six new species, and the diversity and make up of the baeine fauna in southwestern Western Australia.

Convariation of Spider Egg and Clutch Size: The Influence of Foraging and Parental Care

The purpose of this study was to investigate the effects of body size, foraging mode, and parental care on the relationship between clutch size and egg size in spiders. Specifically, covariation of egg size and clutch size with body size was investigated, using data from the literature, in 156 species of North American spiders from 22 families. Variance in clutch size and egg size was found to be mainly attributed to differences among genera. I therefore conducted a comparative analysis at the generic level. Results indicated that clutch and egg size were influenced by body size. Spiders from genera with larger body sizes produced larger offspring and more offspring per reproductive event than spiders from genera with smaller sized species. Relative egg number was inversely related to size of eggs produced, indicating a reproductive trade—off. Web building spiders produced more and smaller eggs than cursorial hunting spiders of a similar body size. Furthermore, cursorial spiders that guard and carry their young produced more young than those that only guard the eggs before hatching or do not guard. However, residual clutch size or residual egg size (residuals from regressions of clutch size and egg size, respectively, against female body size) did not differ among parental care groups. This study suggests that the method of food acquisition and type of parental care contributed to the offspring are associated with clutch size and egg size in spiders.

Development and Reproductive Behavior of Mantispa viridis Walker (Neuroptera: Mantispidae)

The development and reproductive behavior of Mantispa viridis Walker was examined in northwestern South Carolina. Campodeiform first instars actively searched spider egg sacs and halted the development of spider eggs that had advanced to the prelarval or larval developmental stages. M. viridis utilized both viable and inviable spider eggs and completed development on as few as five black widow, Latrodectus mactans (F.), eggs. Developmental time from eclosion to adult emergence averaged slightly less than 24 d. Both mated and unmated females produced egg clutches. However, viable clutches were only produced by mated females. Mated females produced a greater number of clutches each containing more eggs than unmated females. Unmated females produced a small number of eggs that embryonated, and in which a mantispid larva developed. However, larvae in these eggs did not eclose. Males were found to have the intertergal membranes between abdominal segments 3 and 4, and 4 and 5 expanded. These membranes were everted during courtship and apparently emitted a mating or recognition pheromone. Mating behavior and adult longevity are also described.

Seasonal Phenology and Overwintering of Mantispa viridis Walker (Neuroptera: Mantispidae) in South Carolina

Captures of immatures and adults of Mantispa viridis Walker indicate this species has at least three distinct generations per year in the Clemson area of South Carolina, with an occasional fourth one in late fall and early winter. Mark-recapture studies show that M. viridis adults are rarely recaptured. Experiments exposing adults and immatures to ambient fall and winter temperatures in the Upper Piedmont of South Carolina resulted in the death of all adults by December, but 33% of the larvae emerged as adults the following spring from late February through May. The ability to survive prolonged freezing weather as immatures inside spider egg sacs may allow M. viridis to inhabit the colder regions of its range.

The Effect of Host Size on Sex Ratio in the Ichneumonid Wasp, Trychosis cyperia, a Spider Parasitoid

-Since parasitoid wasps can determine the sex of their offspring, they may use this ability to adjust sex in response to differences in the size of their hosts. To test this hypothesis, I measured the size, sex and development times of emerging ichneumonid wasps (Trychosis cyperia Townes), whose larvae are parasitoids of the eggs of crab spiders Misumena vatia (Araneae: Thomisidae), with a single larva per spider clutch. Over 70% of the emerging wasps were females. Host size was positively correlated with size of female, but not male, cocoons and adults. Spider clutches producing male wasps and clutches producing female wasps did not differ in size, but the resulting female wasps were larger than the males. In this sense females used host tissue more efficiently than did males. Probable parental laying dates, emergence dates, and development times of males and females collected in the field but reared in the laboratory did not differ significantly.

Modified Rearing and Maintenance Techniques for Mantispa viridis (Neuroptera: Mantispidae)

Improved techniques were developed for the rearing and maintenance of Mantispa viridis Walker. These have proven highly successful and have eliminated problems encountered by other researchers working on mantispine developmental studies, and should allow subsequent studies to be conducted under standardized conditions. These techniques also have been used in maintaining colonies of beaded lacewings (Neuroptera: Berothidae), various spider egg parasitoids and predators, and are adaptable for other arthropods that require individual confinement.

Speziation bei Parasitoiden am Beispiel von Schlupfwespen (Ichneumonidae: Pimplinae)

Speciation in Parasitoids (Ichneumonidae: Pimplinae)Five species of the ichneumonid genus Tromatobia are currently recognized in Europe. All of them are parasitoids of spider eggs, attacking especially araneid cocoons. There are remarkable differences in biology and development: The Tromatobia species oculatoria and ovivora are oligophagous and bicoltin whereas Tr. ornata (resp. variabilis and forsiusi) is monophagous and univoltin.

Tetrastichinae (Hymenoptera: Eulophidae) associated with spider egg sacs

Aranobroter rayorae, gen. et sp. n., is described as a gregarious predator of spider eggs within egg sacs of Metepeira incrassata (Araneidae) from Veracruz, Mexico. Baryscapus uetzi, sp. n., is described as an internal parasitoid of A. rayorae. The biology of these two species is discussed. A review of Tetrastichinae associated with spider egg sacs includes new North American records.

Colony size and parasitoid load in two species of colonial Metepeira spiders from Mexico (Araneae: Araneidae).

While a number of advantages may result from group living, it may also lead to increased levels of attack by parasites because groups may be easier to find. This leads to the prediction that levels of parasitism should increase with colony size. We test this prediction by comparing colony size and parasitoid load for two species of colonial orb-weaving spiders from Mexico, Metepeira (undesc. sp., tentatively named atascadero) and Metepeira incrassata, which exhibit contrasting levels of social organization and utilize different habitats. For M. atascadero, which occurs solitarily or in small groups in desert/mesquite grassland habitat, rates of egg-sac parasitism fluctuate widely from year to year, and are closely tied to spider egg output. There is no relationship between colony size and rate of parasitism. For colonial M. incrassata, which occur in tropical rain forest/agricultural habitat, rates of parasitism are relatively constant from year to year. However, there is a positive relationship between colony size and rate of parasitism in this species. These differences are discussed with regard to the stability of the two habitats, prey availability, and the foraging behavior of the respective parasitoids.

The biology of Pholcus phalangioides (Araneae, Pholcidae): predatory versatility, araneophagy and aggressive mimicry

Predatory versatility occurs in Pholcus phalangioides (Fuesslin). In addition to building prey‐catching space webs, P. phalangioides invades webs of other spiders and feeds on the occupants. It acts as an aggressive mimic by performing specialized vibratory behaviours to which the prey‐spider responds as it normally would to its own prey. Prey (spiders and insects) is attacked by wrapping. Prey that trips over lines at the edge of a web of P. phalangioides, but fails to enter the web, is successfully attacked: P. phalangioides leans out of its web to throw silk over the prey, keeping as few as two legs on the silk. However, P. phalangioides does not attack prey that is completely away from webs. Occasionally, P. phalangioides feeds on eggs of other spiders and on ensnared insects it encounters in alien webs. Experimental evidence indicates that vision is of little or no importance in the predatory behaviour of P. phalangioides. Although P. phalangioides invades diverse types of webs, in addition to using its own web, its efficiency as a predator varies with web‐type. It is most efficient as a predator of spiders and, especially, insects on its own web, and least efficient as a predator of amaurobiids on their cribellate sheet webs. Sensory, locomotory and other factors which influence differential predatory efficiency are discussed. The behaviour of P. phalangioides is compared to that of Portia, an araneophagic web‐invading salticid, and the results of this study are discussed in relation to hypotheses concerning salticid evolution.