The biology of the mud-wasp Zeta abdominale (Drury) (Hymenoptera: Eumenidae)

The adult female nesting behaviour and biology of the neotropical mud-wasp Zeta abdominale (Drury) was studied in Jamaica. The cell-building behaviour was generally similar to that of Eumenes, but Zeta closed the apical funnel of the cell by moistening and re-moulding it into a plug. Each nest was built by a solitary female, who often built several small, mostly one-celled nests. Females efficiently used mud in cell-building, and small nests were advantageous, in needing less mud per cell and incurring a lower rate of predation than larger nests. Cellwall construction and provisioning were each completed in < 3 h, but a long pause between these activities, probably for feeding, delayed cell completion to 2.33 ± 1.0 days.
The number of active nesting females during a 10-h cycle was influenced by the time of day and weather. A relatively dense population had about 6.4 females ha^-1, whose age distribution, longevity and fecundity were estimated.     

The ecology of two West Indian species of mud-wasps (Eumenidae: Hymenoptera)

Factors affecting the distribution and numbers of the neotropical mud-wasps Zeta abdominale (Drury) in Jamaica and Z. canaliculatum (Oliv.) in Trinidad are discussed. Rainfall was a limiting factor in both aspects of the ecology of the two species. In Jamaica, Z. abdominale was virtually absent from rainfall zones >2540 mm m.a.p. (mean annual precipitation), whereas in Trinidad, Z. canaliculatum hardly inhabited those localities of > 2250 mm m.a.p. Furthermore, the local populations were progressively smaller and more scattered in wetter areas, because consistent rainfall and overcast conditions may result in reduced nesting activity. However, in a favourable locality, numbers may be temporarily increased after rainfall which boosts food supply (caterpillars).
Developmental mortality, at 57.68% and 57.2896 respectively was remarkably similar in Z. abdominale and Z. canaliculatum . The important predators within the cells were Melittobia sp. ( hawaiiensis complex) (Eulophidae) and Amobia fioridensis Townsend (Miltogramminae). In Zeta abdominale total developmental mortality was positively correlated with log,₀ (no. of cells) at different sites; averaging only 33.3% for small populations, but 77.4% for large ones.
Regulation at low numbers ( Z. abdominale ) was probably achieved by harsh physical factors, causing low fecundity, but great survival in the cells and high emigration rate. Where Z. abdominale was numerous, the physical environment was favourable, but developmental mortality was so high, that it is necessary to postulate the immigration of many nesting females.     

Homing Behaviour in Polyergus rufescens Latr. (Hymenoptera,Formicidae)

Homing mechanisms of the European slave-making ant Polyergus rufescens Latr. are investigated by field experiments. The analysis of the behaviour and paths of both homing scouts and raiders after passive displacement showed that: i. Scouts probably home by using a path integration system based on celestial cues; and ii. Displaced raiders do not seem to adopt such a vectorial orientation mechanism. Moreover, we found that passively displaced scouts exhibit a systematic search strategy for the nest after a rectilinear path. By contrast, raiders perform a similar search pattern just after release. Similarities between Cataglyphis and Polyergus homing behaviour are discussed.     

Eco-ethological Factors Affecting the Scouting and Raiding Behaviour of the Slave-making Ant,Polyergus rufescens Latr. (Hymenoptera,Formicidae)

A dulotic colony of the obligatory slave-making ant Polyergus rufescens was monitored daily in the field (Parma, Italy) from 1100–2000 h over the summers of 1991 and 1992. The first P. rufescens workers to emerge from the nest each day were individually marked and their activity was accurately recorded. The path of 47 such individuals (21 over a complete trip) was followed in detail and mapped. Results confirm a clear scouting activity: the route of these workers away from the nest is generally tortuous and time consuming and is followed by a return trip along a different and straighter path. Observations also showed that these scouts recruit nestmates and lead raiding columns towards target nests, confirming their important role in the organization of slave raids. The similarity between routes taken by scouts and raiders during outbound trips indicates the close connection between scouting and raiding activity, which was also recorded in detail since 40 raids were observed. Some experiments analysing the orientation behaviour of inbound columns showed that raiders use a chemical trail (deposited during the outbound run) to lead them back home. The hypothesis of a multiple strategy for the location of host colonies operated by this slave-making species is also discussed.     

Intraspecific slavery inPolyergus rufescens Latr. (Hymenoptera,Formicidae): field and laboratory observations

Summary Four intraspecific slave raids involving 3 colonies of the European amazon antPolyergus rufescens Latr. occurred during hot and sunny afternoons in July 1992 near Parma, Italy. Generally, no fighting between the resident ants and the invaders was recorded, and pillage of the brood lasted just a few minutes. The brood captured during 3 raids was collected and transported ot the laboratory where slavemaker callow workers eclosed and were accepted by both the raiders and hosts present in artificial mixed colonies. This is the first case of functional intraspecific slavery recorded in the field for the obligatory dulotic formicine antP. rufescens.     

A new species of Microsphecodes from Jamaica (Hymenoptera, Halictidae)

A new species of the cleptoparasitic bee genus Microsphecodes Eickwort and Stage (Halictinae: Halictini) is described and figured from a male and female collected in Jamaica. Microsphecodes xaymacensis Engel, sp. n., is distinguished from its congeners on the basis of integumental coloration and sculpturing, and form of the male pygidial plate and genitalia.     

Pollen-Foraging Dynamics of Subalpine Bumblebees (Bombus Latr.)

Abstract A 23-year study on Mount Rainier of nectar-foraging hummingbirds and pollen-foraging bumblebees (Bom-bus Latr.) indicated a constant relative frequency of Bombus species in the area and a wide occurrence of insect species on flowers plus a wide range of flower species pollinated by a single insect. Early-blooming plants had a high queen/worker pollinator ratio, while workers predominated on later-blooming plants. No altitudinal difference in distribution of Bombus species occurred. Analysis of 955 corbicular pollen loads from 1158 bumblebees collected yielded 49.5% monolecty for queens and 34.5% for workers with a wider range for queens than for workers. Colors of corollas photographed in visible and ultraviolet light corresponded to the visual spectra of animal pollinators. In the stable plant-pollinator community investigated, pollinating insect activity appears phenologically controlled by floral anthesis and behaviorally related to floral form and function. Bumblebee tongue length, however. Is not a valid determinant for foraging niche separation except in Castilleja with a deep corolla tube accommodating long tongues of hummingbirds and bumblebees. It is concluded that in a biotic community well-coordinated with the physical environment, limited flower constancy of pollen-foraging pollinators appears to contribute a necessary degree of adaptive versatility through sharing of insect and floral resources. Flower constancy is primarily a function of the circumstance in which a pollinator operates and not simply a characteristic of the pollinator itself.     

Host nest usurpation and colony foundation in the European amazon ant,Polyergus rufescens Latr. (Hymenoptera: Formicidae)

Summary The socially parasitic mode of founding new colonies by queens of the European amazon antPolyergus rufescens was analysed in the laboratory. Newly-mated females of this obligatory slave-maker were individually introduced into queenright and queenless artificially established colonies of bothFormica cunicularia (the slave present in the natal dulotic nest) andF. rufibarbis (another potentialServiformica host). Particular attention was devoted to the behavioural patterns displayed by these young queens during the usurpation phases. Our observations, supported also by video-taping, show that the slave-making female, before laying her eggs, must penetrate the host colony, kill the resident queen, become accepted by the adult workers and appropriate the host brood. The parasite was almost always adopted in the colonies ofF. cunicularia, whereas in the presence ofF. rufibarbis it was generally killed in a short time. The failure in the attempt of usurping the colonies ofF. rufibarbis is discussed in relation to the host specificity typical of this slave-maker. Finally, egg-laying byPolyergus successful usurpers, the subsequent eclosion of the brood, and its complete social integration in the newly-established mixed colonies were also recorded.     

Factors controlling the distribution of a subtropical corn borer,Diatraea grandiosella (Lepidoptera: Pyralidae)

During this century the southwestern corn borer, Diatraea grandiosella (Lepidoptera: Pyralidae), has extended its range from subtropical Mexico into the United States, below 38° N latitude. This maize‐feeding insect is now found from Arizona east to Alabama and north to Kansas, Missouri, and Tennessee. The species has adapted to the shorter growing seasons, longer summer daylengths, and lower winter temperatures present in the southern US than are present in Mexico. Life history, morphological, and behavioral traits were compared for populations of D. grandiosella from southeastern Missouri and southcentral Mexico and revealed differentiation in a suite of characters, some of which show clear adaptation to a northern climate while others are obviously less adaptive. An electrophoretic comparison of enzymes from D. grandiosella from the central portion of its range in the US and from a population from southcentral Mexico indicated that considerable genetic differentiation has occurred. Quantitative genetic studies should be undertaken on the original and dispersed populations to differentiate between those characters that have been directly responsible for the adaptation of this insect to northern maize‐growing regions and those that have changed merely due to genetic correlations with characters undergoing selection. Data from such studies, together with available information about the dispersal of this insect, should provide insight into factors regulating the movement of tropical insects into temperate regions.     

Raiding and Foraging Behavior of the Blood-Red Ant,Formica sanguinea Latr. (Hymenoptera,Formicidae)

In this paper we report the results of a detailed study on the behavioral ecology of slave raiding and foraging activity in the European blood-red ant, Formica sanguinea Latr. The field study was conducted over an unbroken period of 78 days, during which the activity of two dulotic colonies of this facultative slave-maker was observed for 10 h each day. It was possible to observe 26 raids distributed over 23 days, among which 18 were followed by the sacking of nests belonging to the species F. cunicularia, F. fusca, and Lasius emarginatus, whereas 8 failed. Simple, continuous, and simultaneous raids occurred. We recorded the timing, frequency, distance, and direction of slave raids, including the number of participants and the type of booty. Particular attention was devoted to the scouting behavior and raiding organization. Moreover, every day, we observed foraging and predatory behavior, during which adult insects (mainly ants), seeds, and berries were retrieved to the dulotic colonies. On the basis of our observations F. sanguinea seems to be a very efficient slave-maker and predatory species of the Raptiformica subgenus. Moreover, its dulotic behavior may be regarded as a continuation and an expansion of its foraging and predatory behavior, as predicted by Darwin's hypothesis for the origin and evolution of slavery in ants.     

The distribution of freshwater shrimps (Atyidae and Palaemonidae) in Jamaica

The distribution of freshwater shrimps in Jamaica is presented. Atya innocous, Atya lanipes, Atya scabra, Micratya poeyi and Macrobrachium heterochirus were found only in the high-gradient streams characteristic of eastern and north-eastern parishes. Macrobrachium acanthurus, Jonga serrei , and Potimirim mexicana were found only in the low-gradient streams characteristic of western and southwestern parishes. Macrobrachium faustinum, Macrobrachium carcinus , and Xiphocaris elongata were distributed throughout Jamaica. Oxygen, temperature, and current speed were the physical features of the streams most likely influencing this distribution. It was observed that species in high-gradient streams had larvae which required high salinity for development, and those in low-gradient streams had larvae with low salinity requirements. It is argued that larval salinity preferences during the marine planktonic stage of the life history could allow larvae to select an appropriate river prior to its being invaded by juveniles.     

Host-searching behavior ofVenturia canescens (Grav.) (Hymenoptera: Ichneumonidae): Superparasitism

The foraging behavior ofVenturia canescens, a solitary endoparasitoid of lepidopteran larvae, was investigated in the laboratory. FemaleVenturia canescens with a larger number of mature eggs to lay were found to have higher levels of superparasitism (measured as numbers of eggs laid per parasitized host). Increased parasitoid density was found to result in reduced levels of superparasitism by host-deprived (i.e.,undepleted) wasps. Females which had been allowed access to hosts before the experiment (depleted wasps) laid fewer eggs per parasitized host than undepleted wasps, although there was no significant difference in the levels of superparasitism among the depletion periods of 1, 2, 5, and 7 h. It was also found that an egg which was encountered less than 15 min after oviposition was much less likely to be avoided than one which was encountered after more than 15 min had elapsed.     

Intraspecific nest parasitism in the sand waspStictia heros (Fabr.) (Hymenoptera: Sphecidae)

Two forms of intraspecific nest parasitism are described for the neotropical sand waspStictia heros (Fabr.). Females behaving aggressively made aerial attacks on prey-laden females as they approached their nest for provisioning. Attacks resulted in prolonged grappling on the sand, and the relative sizes of the contestants influenced final possession of the prey. Also, the probability that returning females were attacked was directly related to the size of the prey being delivered. Females displaying marauding behavior entered the nests of other females, removed prey, and deposited it in their own nest. Females usually raided nests that were near their own nest and tended to concentrate raiding attempts on nests that previously yielded prey. We also describe the behavior associated with the delivery of hunted prey and examine possible interrelationships between wasp size, prey size and hunting trip duration.     

The comparative distribution and population dynamics in Trinidad of Sceliphron fistularium (Dahlbom) and S. asiaticum (L.) (Hymenoptera: Sphecidae)

Two sphecid wasps, Sceliphron asiaticum (L.) and S. fistularium (Dahlbom), which build mud nests and capture spider prey, had overlapping but distinctly different distributions in Trinidad. Sceliphron asiaticum was associated with drier (<2000 mm mean annual precipitation) and less forested areas. The analysis of existing data on these species revealed a similar differential distribution throughout the neotropics. Based on the dissection of their old nests collected at 42 sites in Trinidad, retrospective life tables were constructed and estimates of fecundity made. Sceliphron asiaticum tended to form denser nesting associations and, while most of the common parasitoids were shared, had overall higher developmental mortality. Although such mortality was density-dependent in both species, where the two wasps nested together mortality from Melittobia (Eulophidae, Chalcidoidea) was higher in S. asiaticum . Both species were protarrhenotokous and had similar field fecundities (7–8/♀), but the rate of oviposition may be greater in S. asiaticum since far less mud was used in the construction of its cells. Both species had >50° mortality of the females between emergence and starting to nest. The regulation of numbers of these wasps in relation to that of S. assimile (Dahlbom) in Jamaica is discussed.