Cephalonomia Waterstoni Research Articles

Abundance and diversity of insects associated with stored grains and tamarind in Nigeria

Detailed information on insect pests of stored grains in Nigeria is lacking. A two-year survey was conducted to determine the species composition and abundance of insects associated with maize, millet, rice, sorghum and tamarind in eighteen locations across five agro-ecological zones in Nigeria. Sixteen coleopteran, lepidopteran and hymenopteran species were associated with stored products, with high species richness on cereal grains but low species richness on tamarind. Most of these insects are polyphagous on cereal grains, whereas the tamarind weevil Sitophilus linearis (Herbst, 1797) (Curculionidae), and Caryedon serratus (Oliver, 1790) (Chrysomelidae) were found only on tamarind in this study. The maize weevil Sitophilus zeamais (Motschulsky, 1758), rice weevil Sitophilus oryzae (Linneaus, 1763), lesser grain borer Rhyzopertha dominica (Fabricius, 1792) (Bostrichidae), rusty grain beetle Cryptolestes ferrugineus (Stephens, 1831) (Laemophloeidae) and red flour beetle Tribolium castaneum (Herbst, 1797) (Tenebrionidae) were most abundant on stored grains. The tamarind weevil, C. serratus and the sawtoothed grain beetle Oryzaephilus surinamensis (Linneaus, 1758) (Silvanidae) were most abundant on tamarind. The hymenopterans Theocolax elegans (Westwood, 1874) (Pteromalidae), Anisopteromalus calandrae (Howard, 1881) (Pteromalidae) and Cephalonomia waterstoni (Gahan, 1931) (Bethylidae) were the dominant parasitoids of larvae and pupae of the storage pests. Simpson index of diversity of insect species across locations ranged from low (0.63) to high (0.89).

Olfactory host location and host preference of Holepyris sylvanidis (Hymenoptera: Bethylidae) and Cephalonomia waterstoni (Bethylidae), two natural enemies of Tribolium and Cryptolestes species.

Parasitoids can suppress populations of their host and thus play a primary role in Integrated Pest Management. In the stored product environment, stimuli deriving from plant products, damaged plant products and hosts might be important for host location by the parasitoids. We studied foraging cues in Holepyris sylvanidis (Hymenoptera: Bethylidae), a larval parasitoid of Tribolium species and Cephalonomia waterstoni (Bethylidae), a natural enemy of the rusty grain beetle Cryptolestes ferrugineus (Coleoptera: Cucujidae). Our studies in a fourchamber olfactometer revealed that the host complexes of both Tribolium species and different living host stages attract naive H. sylvanidis females, whereas no reaction was observed to uninfested substrates. The olfactory response of C. waterstoni was found to be strongly elicited both by chemicals emitted by the dust, adult C. ferrugineus and C. ferrugineus third and fourth instar larvae. Our findings may contribute to the development of biological control strategies of T. castaneum, T. confusum and C. ferrugineus with parasitoids.

Olfactory host location in the rusty grain beetle parasitoid Cephalonomia waterstoni (Gahan) (Hymenoptera: Bethylidae)

Parasitoids can suppress populations of their host and thus play a primary role in Integrated Pest Management. The parasitic wasp Cephalonomia waterstoni Gahan (Hymenoptera: Bethylidae) is a natural enemy of the rusty grain beetle Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae). In the stored product environment, stimuli deriving from plant products, damaged plant products and hosts might be important for host location by the parasitoids. We tested the response of female parasitoids to odours deriving from infested and uninfested plant products, the grain dust produced by feeding primary pests, and various life stages of the rusty grain beetle. The olfactory response of C. waterstoni was found to be strongly elicited both by chemicals emitted by the dust, adult C. waterstoni and C. waterstoni third and fourth instar larvae. Our findings may contribute towards biological control of C. ferrugineus and the chemical ecology of olfactory host location by C. waterstoni.

Sampling arthropod pests and natural enemies in stored barley

Application of pest management programs for the food industry reduces pesticide applications, increases the effectiveness of pest suppression to acceptable levels and reduces the cost and risk of negative non-target effects. In these programs, efficient sampling is a decisive factor for undertaking management measures. In this study, a one year survey of arthropods attacking stored barley and their natural enemies was conducted in two experimental piles, in which no fumigation was applied. Sampling was performed on a monthly basis with a grain sampling trier, with pitfall traps and yellow sticky traps. The parasitoid Anisopteromalus calandrae was released twice in one of the piles with the aim of testing its establishment and control capacity on the infesting beetles.Seven coleopteran and one psocid species formed the assemblage of pests that attacked the two barley piles, among which Sitophilus granarius, Rhyzopertha dominica and Latheticus oryzae were the most abundant species. Two parasitoids, A. calandrae and Cephalonomia waterstoni, and one predator, Withius piger, were the beneficial organisms found. Two releases of A. calandrae were successful in establishing the parasitoid, but they were not enough for controlling either S. granarius or R. dominica. Pitfall traps captured the same complex of species as the grain sample trier but the abundance of each species was not always the same in both devices. These traps were good for detecting the early presence of most species. Yellow sticky traps only captured some species from the pest complex and trapped high numbers of the parasitoid A. calandrae. They can be of help as indicators of the colonization of some specific pests, such as R. dominica, in the first weeks of the invasion process.

Interaction of Mattesia oryzaephili (Neogregarinorida: Lipotrophidae) with Cephalonomia spp. (Hymenoptera: Bethylidae) and their hosts Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) and Oryzaephilus surinamensis (Coleoptera: Silvanidae)

The neogregarine, Mattesia oryzaephili, is pathogenic for several stored-grain pest insects, including the sawtoothed grain beetle, Oryzaephilus surinamensis, and the rusty grain beetle, Cryptolestes ferrugineus. It also infects their respective bethylid parasitoids, Cephalonomia tarsalis and Cephalonomia waterstoni. Male wasps do not attack the beetle larvae and do not become infected, but the disease is transmitted per os to nearly all female wasps when they paralyze or feed on infected hosts. The mean survival time of infected female C. tarsalis after exposure to heavily infected O. surinamensis was 20.0 days, while that of healthy C. tarsalis was 38.0 days. For C. waterstoni females, the mean survival times were 36.1 days when infected and 45.9 days when uninfected. The long survival time of infected wasps fosters oviposition and inoculum deposition in the hosts’ habitat. The wasps sting and bite infected host larvae and sometimes oviposit. Wasp progeny that are deposited on infected host larvae rapidly succumb to M. oryzaephili. Two-hour wasp conWnement with patently infected larvae resulted in no transmission from C. waterstoni to C. ferrugineus and 4% transmission from C. tarsalis to O. surinamensis. Contamination of wheat by wasps after they had attacked infected beetles resulted in 8.9% infection of O. surinamensis that developed from eggs that were placed on the contaminated wheat. It is proposed that Cephalonomia spp. can be used as a means to inoculate M. oryzaephili into pest grain beetle populations and aid in its dispersal to help suppress pest populations. Published by Elsevier Inc.

Suppression of Beetles in Stored Wheat by Augmentative Releases of Parasitic Wasps

Field studies were conducted to assess the effectiveness of the parasitoid wasps, Cephalonomia waterstoni (Gahan), and Choetospila elegans (Westwood), for controlling Cryptolestes ferrugineus (Stephens), rusty grain beetle and Rhyzopertha dominica (F.), lesser grain borer. On 6 July 1993 and 7 July 1994, adults of both C. ferrugineus and R. dominica were released at monthly intervals into 6 steel grain bins each containing 27.2 t of hard red winter wheat, Triticum aestivum L. Adults of both parasitoid species were released into 3 of the bins 21 d after the 1st beetle release. The amount of suppression of C.ferrugineus by C. waterstoni could not be measured in either year of this study because C. waterstoni infested the control bins. However, C. elegans was effective in suppressing R. dominica populations. In 1993 and 1994, R. dominica populations were suppressed by 98 and 91% compared with the control bins. After 198 d from initial beetle release in 1993, the treatment bins averaged 0.05 R. dominica per kilogram and the control bins averaged 2.06 R. dominica per kilogram. After 131 d from initial beetle release in 1994, the treatment bins averaged 6.94 R. dominica per kilogram and the control bins averaged 81.03 R. dominica per kilogram.

Simulation Model of Cephalonomia waterstoni (Hymenoptera: Bethylidae) Parasitizing the Rusty Grain Beetle (Coleoptera: Cucujidae)

We have developed a simulation model of parasitic grain wasp, Cephalonomia waterstoni (Gahan), parasitizing the rusty grain beetle, Cryptolestes ferrugineus (Stephens). The model predicts host and parasitoid phenology based on grain temperature, using a distributed– delay method to simulate variance in developmental rate. The model accurately predicted both the time and magnitude of peak parasitoid density. Changing the timing of parasitoid release had a greater effect than releasing more parasitoids. Releasing parasitoids at day 20 instead of day 40 reduced the maximum host population by 75%. Parasitoids are most effective when releases are timed so that parasitoids find the 1st–produced 4th–instar. This model should be a valuable tool for developing a biological control program for C. ferrugineus on stored wheat. It can be used to predict the optimum time of release, the number of parasitoids to release, and the effects of other controls such as fall aeration.

Comparative Analysis of Cuticular Hydrocarbons from the Ectoparasitoids Cephalonomia waterstoni and Laelius utilis (Hymenoptera: Bethylidae) and Their Respective Hosts, Cryptolestes ferrugineus (Coleoptera: Cucujidae) and Trogoderma variabile (Coleoptera: Dermestidae)

Cuticular hydrocarbons have been identified from the immatures and adults of two bethylid wasps and their larval beetle hosts. Cephalonomia waterstoni Gahan is host specific on Cryptolestes ferrugineus (Stephens), whereas Laelius utilis Cockerell is commonly associated with a variety of dermestid larvae, including Trogoderma variabile Ballion. The cuticular hydrocarbons of C. waterstoni larvae consist of n-alkanes (C21-C33), 2-, 3-, 5-, 7-, 11-, and 13-methyl alkanes, one dimethyl alkane (11,15-dimethyl C27), and a C31 monoene and diene. The cuticular hydrocarbon composition of their beetle host differs somewhat, consisting of n-alkanes (C25-C32), 3-, 5-, 11-, and 13-methyl alkanes, a series of Z-8/Z-9-monoenes, and a series of dienes with the double bonds separated by 12 methylene units. No dimethyl alkanes are present in the C. ferrugineus larvae. Considerable ontogenetic changes in cuticular hydrocarbon composition occur when C. waterstoni eclose to adults. Although both sexes contain the same major cuticular hydrocarbons, their relative abundances vary. In addition to n-alkanes (C23-C27), 2-, 3-, and 5-methyl alkanes, 5,15-, 5,17-, and 5,19-dimethyl alkanes, and a series of Z-11-monoenes are present in both sexes. In addition, the males possess small quantities of Z-7-monoenes. The males have the monoenes as their major components, whereas the females have the 5-methyl alkanes and the dimethyl alkanes as their major components. The cuticular hydrocarbon composition of L. utilis and its host T. variabile differs considerably from the Cephalonomia-Cryptolestes pairing. The major components of the Laelius larvae consist of n-alkanes (C23-C33), 3-, 5-, 13-, and 15-methyl alkanes, and a series of Z-9-monoenes. The T. variabile larval hydrocarbons consist only of n-alkanes (C22-C35) and 3-, 5-, and 13-methyl alkanes. No unsaturated components were detected. As with C. waterstoni, considerable ontogenetic changes in hydrocarbon composition occur for L. utilis upon adult eclosion. Unlike C. waterstoni, however, only slight differences in composition occur between the sexes. The adult Laelius hydrocarbons consist of n-alkanes (C21-C29), 2-, 3-, 7-, 9-, and 13-methyl alkanes, and a series of Z-9-monoenes.

Trophic Structure of the Community in the Guano of the Evening Bat Nycticeius humeralis in Indiana

The most abundant organisms in the fauna of the guano of the evening bat Nycticeius humeralis, roosting in a church belfry in Clay County, Indiana, were three species of tenebrionid beetles, Tenebrio molitor, Tribolium ferrugineum and Neatus tenebrioides; a histerid beetle, Carcinops quattuordecimstriata, and the larvae of a fly, Stomoxys calcitrans (Muscidae). Adult milichiid flies, Leptometopa latipes, larval anthomyiid flies, Fannia canicu- laris; a bethylid wasp, Cephalonomia waterstoni, and two beetles, Attagenus piceus (Dermes- tidae) and Oxypoda sagulata (Staphylinidae) were other important components of this com- munity. A trophic diagram is given for this community.

Temperature-Dependent Functional Response of the Parasitoid Cephalonomia waterstoni (Gahan) (Hymenoptera: Bethylidae) Attacking Rusty Grain Beetle Larvae (Coleoptera: Cucujidae)

The effects of host density and temperature on the functional response of the bethylid parasitoid Cephalonomia waterstoni (Gahan) attacking fourth-instar rusty grain beetle, Cryptolestes ferrugineus (Stephens) were examined. Five temperatures and six host densities were used. A type II functional response model was fit separately to each temperature. The maximum attack rate ranged from 7.5 larvae/12 h at 25°C, to 2.9 larvae/12 h at 38°C. Handling time and instantaneous search rate varied with temperature. A new functional response equation was developed in which handling time is a quadratic function of temperature. This equation explained 83% of the variation in attack rate. Although instantaneous search rate was also affected by temperature, it was sufficient to make only handling time a function of temperature because the two parameters were highly correlated.

Larval Trails of Cryptolestes ferrugineus (Coleoptera: Cucujidae) as Kairomonal Host-Finding Cues for the Parasitoid Cephalonomia waterstoni (Hymenoptera: Bethylidae)

Wandering late fourth instars of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), leave a substrate-borne chemical trail that serves as a kairomone for their host-specific bethylid parasitoid Cephalonomia waterstoni Gahan. Male C. waterstoni show no trail-following behavior to this kairomone. Experienced C. waterstoni females follow trails of ≥0.0001 larval equivalents per centimeter (LE/cm), whereas naive females show no trail following responses to dosages of <0.1 LE/cm. A dose-dependent response for time spent on the trail and length of trail followed was shown by the parasitoid to natural trails. The time spent by the parasitoid on artificial trails produced by using beetle extracts also showed a dose dependent response. The parasitoid shows weak or nonexistent trail-following responses to hexane extracts of larvae of the flat grain beetle Cryptolestes pusillus (Schonherr) or the red flour beetle Tribolium castaneum (Herbst). The trails of C. ferrugineus larvae are only moderately persistent. Natural trails aged on filter paper elicit trail-following responses by the parasitoid for less than one week. Artificial beetle extract trails on ground glass plates elicited trail following by the parasitoid for almost two weeks. The disappearance of both natural and solvent extract kairomonal trails follows an exponential decay model.

Seasonal Variation of Stored Wheat Environment and Insect Populations

Temperatures of wheat in the top meter in on-farm cylindrical metal bins in Kansas were uniform and within a favorable range of 27–34°C for the first 12 wk and then declined at rates ranging from 1.3 to 2°C/wk. Cooling of grain from the outside and surface inward and downward resulted in temperature gradients. Grain moisture in the top 0.5 m declined during the first 12 wk and then increased to levels well above initial moisture. Elsewhere in the top meter, wheat retained its initial moisture level except for the tendency of grain near the bin wall to be drier. Population growth rate of the dominant species, Cryptolestes ferrugineus (Stephens), declined over the wheat storage period in the top meter of grain as a result of first the parasite Cephalonomia waterstoni Gahan and then falling temperatures. C. ferrugineus adults showed only a slight tendency to move toward the warmer or moister parts of the bin. Trogoderma glahrum (Herbst) adults and larvae and Trogoderma inclusum LeConte adults, the next most abundant species, were found mainly near the bin wall. Rhyzopertha dominica (F.) were first detected after 12 wk and were found only in the center.

Host Preference of Cephalonomia Waterstoni Gahan, a Bethylid Parasitoid of Laemophloeus Species

F. Cephalonomia waterstoni Gahan, a bethylid parasite of Laemophloeus, shows a different degree of preference for several species of the host. Preference is measured by the relative numbers of the various host species which are attacked and oviposited upon in a certain period of time. The two are not necessarily proportional, but probably are. 2. The relative attractiveness of four species of Laemophloeus was compared in the laboratory. L. ferrugineus and an unidentified species (see Appendix) are about equally attractive, L. minutus comes next and L. turcicus is least preferred of these four. 3. When confined with one or both of the non-preferred species the incidence of parasitism rises, more so on L. minutus than on L. turcicus. 4. No food conditioning effect was detected on L.sp.n.det. but after 1-9 geverations on L. minutus the parasite's preference for that host increased but did not surpass are mixed together in a common vessel. 5. Cephalonomia can discriminate between L. minutus and L. ferrugineus when they the primary preference for L. ferrugineus. 6. Discrimination in oviposition is still possible when paralyzed larvae of L. minitus and L. ferrugineus are offered. This rules out several factors from the list of possible ones utilised by the parasite in selecting its host or which prevent it from utilising certain hosts. Examples are movement and silk, the first a possible stimulus and the second a possible barrier. 7. The evidence put forward in this paper supports the hypothesis that parasites may be stimulated to attack and oviposit, although to a lesser degree, by qualities of hosts related to their normal host. The effective stimulus may take the form of a range of related stimuli, the effectiveness at any point on the range depending on the physiological condition of the parasite. Unless its threshold is low the parasite may not be stimulated by the limits of the range. 8. The type of differential host preference described in Cephalonomia waterstoni may be advantageous to the species in that a secondary host may replace the preferred one in a season or region in which the latter is absent or scarce. In a normal season the secondary host will not be heavily parasitized and may form a 'host reservoir'.

THE BIOLOGY OF CEPHALONOMIA WATERSTONI GAHAN

Life history and morphological studies were made on Cephalonomia waterstoni Gahan, a hymenopterous parasite on the larval and pupal stages of the rusty grain beetle, Laemophloeus ferrugineus (Steph.). At 90° F. and 65 to 75% relative humidity the whole life cycle of C. waterstoni is completed within 12 to 13 days. The adult life span of females is about three weeks, while that of males is much shorter. The male, which prior to this work was unknown, can easily be distinguished from the female by its smaller size, its less rectangular-shaped head, and its longer antennae. The first flagellar segments of the males are brownish-black in color while those of the females are yellowish. The ratio of females to males is somewhere near 2:1. The ease with which the parasite C. waterstoni can be reared in large numbers in the laboratory, and its remarkable ability to check infestations of L. ferrugineus under experimental conditions, indicate that this species might be of value in biological control programs for L. ferrugineus in warehouses, mills, and elevators.