Predatory Gall Midge Research Articles

Intraguild species presence alters Aphidoletes aphidimyza (Diptera: Cecidomyiidae) and Aphidius gifuensis (Hymenoptera: Braconidae) foraging responses.

The predatory gall midge, Aphidoletes aphidimyza (Rondani), and tobacco aphid cocoon wasp, Aphidius gifuensis Ashmead, are important natural enemies of Myzus persicae (Sulzer) (Hemiptera: Aphididae). Predation by A. aphidimyza and A. gifuensis can regulate M. persicae; however, how interspecific interference competition affects their foraging efficiency is unknown. Here, we investigated the consumption and parasitization abilities of A. aphidimyza 3rd instar larva and A. gifuensis adults under various conditions. Consumption of parasitized aphids by A. aphidimyza 3rd instar larvae was significantly lower than that of nonparasitized controls, with a substantial increase in handling time. The presence of A. gifuensis adults did not significantly affect the predation capacity of A. aphidimyza larvae. Relative to controls, A. aphidimyza larvae predation trace (PT) and imago activity significantly decreased A. gifuensis parasitism rates at different aphid densities. Further, A. aphidimyza larvae PT increased the A. gifuensis handling time of M. persicae, whereas the presence of A. aphidimyza adults had the opposite effect. Coexistence with heterospecific natural enemies reduced the parasitic capacity of A. gifuensis, whereas A. aphidimyza larvae predation capability was influenced to a lesser extent. Our results demonstrate that intraguild interactions strongly influence the predatory and parasitic efficacy of A. aphidimyza and A. gifuensis, although the effect on A. gifuensis was more pronounced. For effective biological control of M. persicae using A. aphidimyza and A. gifuensis, we recommend releasing A. aphidimyza first to mitigate intraguild predation and enhance the overall success of the pest control program.

Evaluation of pongamia oil soap against red spider mites, Tetranychus urticae Koch and its effect on mite predators in brinjal ecosystem

The efficacy of pongamia oil soap was tested on red spider mites and on its predators (rove beetle, Oligota sp. and predatory gall midge, Feltiella acarisuga Vallot). Pongamia oil soap at 0.6, 1, 2 and 3 per cent along with neem oil 0.6 per cent, soap solution 0.5 per cent and thiamethoxam 25 WG were investigated and observations were recorded on, a day prior to and, 1, 3, 5, 7 and 14 days after spray application. The results revealed that pongamia oil soap @ 3, 2 and 1 per cent shown mite population reduction up to 86.50, 84.57 and 79.27 per cent respectively. Richness of mite predators didn’t vary significantly at one day after spray and the maximum population was observed in soap solution - (4.33/5 plants). Population of mite predators was relatively high at 14 days after spray with soap solution (35.67 per five plants) which was at par with pongamia oil soap @ 0.6, 1 and 2 per cent.

Effect of Temperature on the Development and Survival of Feltiella Acarisuga (Vallot) (Diptera: Cecidomyiidae) Preying on Tetranychus Urticae (Koch) (Acari: Tetranychidae).

Simple SummaryThe predatory gall midge is one of the most effective natural enemies of the two-spotted spider mite, which is an economic pest causing a severe impact on a wide variety of plants worldwide. In general biocontrol programs, midges have been reared in insectaries and released into agriculture fields or greenhouses. In this study, we tested the effect of temperature on the development and survival of the predatory gall midge. The results showed that temperature played a crucial role in determining the emergence time and survival rate at each development stage. We described the responses to temperatures using several equations and estimated the values for explaining the observed biological patterns. The developed equations suggested that 23.3–28.7 °C temperatures were suitable for the total immature stage. In contrast, conditions around 8 °C and 35 °C should be avoided due to the high mortality. These results can help to determine the effective temperatures for both rearing and releasing, and ultimately contribute to the successful biological control of the spider mite.The predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae), is an acarivorous species that mainly feeds on spider mites (Acarina: Tetranychidae). Because of its cosmopolitan distribution and predation efficacy, it is considered an important natural enemy available as a biological agent for augmentative biocontrol. However, despite its practical use, the thermal development and survival response to temperature have not yet been fully studied. In this study, we investigated the stage-specific development and survival of F. acarisuga at seven temperatures (11.5, 15.7, 19.8, 23.4, 27.7, 31.9, and 35.4 °C) to examine the effect of temperature on its lifecycle. All developmental stages could develop at 11.5–31.9 °C, but the performance was different according to the temperature. From the linear development rate models, the lower development threshold and thermal constant of the total immature stage were estimated at 8.2 °C and 200 DD, respectively. The potential optimal and upper threshold temperatures for the total immature stage were estimated as 29.3 and 35.1 °C using a non-linear development model. The operative thermal ranges for development and survival at 80% of the maximum rate were 24.5–32.3 and 14.7–28.7 °C, respectively. Thus, it was suggested that 24.5–28.7 °C was suitable for the total immature stage. In contrast, conditions around 8 °C and 35 °C should be avoided due to the lower development rate and high mortality. Our findings provide fundamental information for an effective mass-rearing and releasing program of F. acarisuga in an augmentative biocontrol program and help to predict phenology.

Interactions of Acariphagous Arthropods in the System “Host Plant—Spider Mite Tetranychus urticae Koch (Acarina, Tetranychidae)—Predatory Mite Phytoseiulus persimilis Ath.-H. (Parasitiformes, Phytoseiidae) and Predatory Midge Feltiella luboviae Fedotova et Kozlova (Diptera, Cecidomyiidae)” on Cucumber Cultivars

Relations between the predatory species were studied in the tritrophic system “plant—spider mite Tetranychus urticae—predatory mite Phytoseiulus persimilis + predatory gall midge Feltiella luboviae” on Ginga F1 and Muromsky 36 cucumber cultivars, differing in their resistance to the phytophage. It was shown that the formation and functioning of the consortium were largely influenced by the resistance properties of the cucumber cultivars and the bioecological features of the consorts. The acariphages most effectively suppressed the pest at the initial stage of consortium formation, when their first generation was active. The efficiency of the predatory midge F. luboviae on the susceptible cucumber cultivar was lower in the presence of the predatory mite Ph. persimilis. The resistant cultivar not only compensated for the negative effect of one predator (Ph. persimilis) on the oviposition behavior of the other predator (F. luboviae), but also increased the efficiency of combined use of the acariphages as compared to their separate application.

Effects of prey aphid species on the abundance of a parasitoid and two predator species in aphid colonies attended by ants on citrus

AbstractThis study focused on three species of enemies, the parasitoid wasp Lysiphlebus japonicus Ashmead (Hymenoptera: Aphidiidae), the ladybird Scymnus posticalis Sicard (Coleoptera: Coccinellidae) and the predatory gall midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae), all of which are able to exploit aphids attended by ants. I experimentally evaluated the effects of prey aphid species on the abundance of each of the three enemy species in ant‐attended aphid colonies on citrus. The aphids compared were Aphis gossypii Glover versus Aphis spiraecola Patch in late spring, and Toxoptera citricidus (Kirkaldy) versus A. spiraecola in late summer (all, Hemiptera: Aphididae). Colonies of the three aphid species were attended by the ant Pristomyrmex punctatus Smith (Hymenoptera: Formicidae). The initial number of attending ants per individual aphid did not differ significantly between the colonies of the two aphid species compared in each season. Between A. gossypii and A. spiraecola, there was no significant difference in the number of mummies formed by the parasitoid or foraging larvae of each of the two predators per aphid colony. A significant difference was detected between T. citricidus and A. spiraecola for each of the three enemy species, with a far greater number of L. japonicus mummies in T. citricidus colonies and distinctly more larvae of each of the two predators in A. spiraecola colonies. Thus, the abundance of each of the three enemy species in ant‐attended aphid colonies was significantly influenced by the species of the prey aphids, with the three enemies showing different responses to the three aphid species.

Plant fertilization helps plants to compensate for aphid damage, positively affects predator efficiency and improves canola yield

Fertilizers utilization does not only play an important role in increasing the crop yield, but also they may influence the plant nutritional quality, thereby it affects the ecological interactions between herbivores and their natural enemies. In a field study, the effect of nitrogen fertilization (0, 75, 150 and 225 kg N ha−1) on population of mustard aphid, Lipaphis erysimi Kalt. (Hemiptera: Aphididae) and predatory gall midge, Aphidoletes aphidimyza (Diptera: Cecidomyiidae), in canola (Brassica napus L.), as well as their interactive impact on the plant yield was investigated. The population of aphid and predator were positively affected by nitrogen fertilization; the maximum abundances of which were observed in plants with 150 and 225 kg N ha−1 applied. However, predator to prey ratio was lower in the highest N level in comparison with the moderate level. The maximum suppression of the aphid by the predator was also observed in the moderate N level. The interactive effect of nitrogen fertilizing and the predator presence positively influenced the canola grain yield. The lowest yield losses due to aphid infestation were observed in plants fertilized with 150 kg N ha−1 in the presence of the predator. In this fertilization level, the plants could compensate the aphid damage more than the other treatment levels; hence, they produced significantly more grain yield. These findings indicate that adequate plant nutrition can help plants compensate for aphid damage and also positively affect the predator efficiency, leading to an improvement in the canola yield.

CONFIRMATION OF PRESENCE OF A PREDATORY GALL MIDGE, Feltiella acarisuga, (Vallot, 1827) AND STAPHYLINID PREDATOR Oligota oviformis Casey, 1893 OF A TWO SPOTTED SPIDER MITE (Tetranychus urticae, Koch, 1836) IN SLOVENIA

The two spotted spider mite, Tetranychus urticae C. L. Koch, 1836 is one of the most important pests of greenhouse crops worldwide. Due to its polyphagic range of hosts and rapid development it forms great populations and as such represents a suitable host/prey for lots of natural enemies usable in biological control. Most commonly used predators of Tetranychid mites are predatory mites (Phytoseiulus persimilis Athias-Henriot, 1957, Amblyseius swirskii Athias-Henriot, 1962 ,…), but among most voracious predators is the larva of a predatory gall midge, Feltiella acarisuga (Vallot, 1827) that was found also in greenhouses of the Biotechnical Faculty in Ljubljana on eggplant leaves in 2017. Besides the predatory gall midge also another predator, staphylinid Oligota oviformis Casey, 1893 beetles and larvae were found in great numbers. After positive identification of F. acarisuga found naturally in Slovenia, it can be added to the list of indigenous species of natural enemies and thus can be used in biological control programs in greenhouse crop protection against spider mites.

New Record of Predatory Gall Midge, Lestodiplosis triangulata Grover and Bakshi, 1978 from Andaman Islands, India

New Record of Predatory Gall Midge, <i>Lestodiplosis triangulata</i> Grover and Bakshi, 1978 from Andaman Islands, India

Interactions in the tritrophic system “Host plant–spider mite Tetranychus urticae Koch (Acarina, Tetranychidae)–predatory midge Feltiella sp. (Diptera, Cecidomyiidae)” on cucumber cultivars

A study of interspecific relations in the tritrophic system “plant–spider mite–predatory gall midge Feltiella sp.” on cucumber cultivars differing in their resistance to the phytophage has shown that the formation and functioning of the consortium are largely influenced by genetic properties of the plant and ecological features of the consorts. The nature of ecological association of the predator and its prey in the tritrophic system appears to depend on the cucumber genotype and on the morphological and physiological state of the plant. It has been shown that at different densities of the spider mite on cucumber plants, the predator increases the plant resistance by reducing the pest density, while genetic resistance of the plant restricts the phytophage densities thereby increasing the efficiency of the acariphage.

Functional Response of Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae) to Aphis gossypii Glover (Hemiptera: Aphididae): Effects of Vermicompost and Host Plant Cultivar.

Interactions between natural enemies and herbivores may be affected by application of fertilizers and different cultivars. We investigated the functional response of the predatory gall midge, Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae) larvae to the nymphs of the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), reared on two commonly grown cucumber cultivars in Iran (Khasib and Karim) treated with different vermicompost/soil ratios (0:100, 10:90, 20:80, and 30:70%). Based on logistic regression analysis, A. aphidimyza revealed a type II functional response to the aphid in all treatments. Attack rates and handling times of A. aphidimyza larvae on different vermicompost/soil ratios ranged from 0.076 to 0.140 h(-1) and 0.969 to 1.164 h on Khasib and from 0.092 to 0.123 h(-1) and 0.905 to 1.229 h on Karim, respectively. Furthermore, increasing the density of the melon aphid on both cultivars amended with vermicompost/soil ratios resulted in increased prey consumption by the predator. Density of trichomes increased when plants received higher concentrations of vermicompost. So, trichomes may be responsible for different attack rates and handling times of A. aphidimyza on both cultivars.

Prey Preference of Aphidoletes Aphidimyza on Acyrthosiphon Pisum: Effect of Prey Color and Size

Color polymorphism in insects as well as factors contributing to its occurrence and maintenance have been of a great interest. Pea aphid (A. pisum) exhibits a noteworthy color polymorphism which occurs as red and green. The preference of the predatory gall midge Aphidoletes aphidimyza (Rondani) for the two color morphs of pea aphid at two life stages (adult and second instar) was investigated. Red adults, red nymphs, green adults, and green nymphs were offered to the larvae of the predator in different sets. The larvae attacked red aphids more than green ones of a same size. But whenever adults were offered along with nymphs, the nymphs experienced significantly more attacks. Although visual cues could result in more predation on red aphids, our findings showed that the size of aphids was the more important factor. The results showed that previous findings, suggesting more predation on the red morph, are valid when the same size of aphids is used. The ovipositing females exhibited no differences in oviposition choice between stalks infested with either of two colors.

Effects of aphid honeydew sugars on the longevity and fecundity of the aphidophagous gall midge Aphidoletes aphidimyza

The predatory gall midge Aphidoletes aphidimyza, which is used for augmentative biological control of aphids in greenhouses, uses aphid honeydew as an energy source. Currently, Rhopalosiphum padi on barley plants and Melanaphis sacchari on sorghum plants are used as the banker plant systems for A. aphidimyza to control Aphis gossypii on eggplant in Japan. We analyzed the sugar components of the honeydew of these three species by HPLC. The major components of honeydew were sucrose, fructose, and melezitose for A. gossypii; glucose and fructose for R. padi; and glucose, fructose, and melezitose for M. sacchari. Maltose and trehalose were minor components of the honeydew of these species. We investigated the influence of sugars, including three artificial aphid honeydews, six sugar components, and distilled water, on the longevity of unmated A. aphidimyza. Both females and males attained the greatest longevity on sucrose and artificial honeydew of A. gossypii. Mean longevities of both females and males were shortest when they were provided only with water. We conducted another experiment in which a mated female was released in a cage with an eggplant seedling infested with A. gossypii and fed with sucrose or only water. Females fed with sucrose lived significantly longer and had higher lifetime fecundity than those fed only water.

Functional Responses and Prey-Stage Preferences of a Predatory Gall Midge and Two Predacious Mites with Twospotted Spider Mites,TetranychusUrticae, as Host

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an important pest of vegetables and other economically important crops. This study evaluated the functional responses and prey-stage preferences of three species of predators, a predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae), and two predatory mite species, Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) and Amblyseius swirskii (AnthiasHenriot), with T. urticae as the host, under laboratory conditions. The results showed that F. acarisuga was highly effective and the two species of predacious mites were moderately effective in feeding on T. urticae eggs. Logistic regression analysis suggested Type II (convex) functional responses for all three species. However, based on the estimates of the handling time and the attacking rates, the three predators had different predation capacities. Among the three species, F. acarisuga had the highest predation on T. urticae. The maximum daily predation by a larval F. acarisuga was 50 eggs/day, followed by a female N. californicus (25.6 eggs/day) and a female A. swirskii (15.1 eggs/day). A female N. californicus produced more eggs than a female A. swirskii did when they both fed on T. urticae eggs. In addition, all three predator species had no preystage preference for either prey eggs or nymphs. The findings from this study could help select better biological control agents for effective control of T. urticae and other pests in vegetable productions.

When to estimate sex ratio in natural populations of insects? A study on sex ratio variations of gall midges within a generation

AbstractPrecise estimation of arthropods' sex ratio is an important issue in a wide range of ecological studies and biological control programs. Although, in many cases changes in arthropods' sex ratio may be under the control of parents or some symbiotic microorganisms, biased sex ratios in some other species are caused by some extrinsic factors, neglect of which may lead to under/overestimation of true sex ratio. In this paper, we pursued those factors that cause false estimation of sex ratio in insects' species. We studied the predatory gall midge, Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae), an important biological control agent of aphids, that shows protandry (i.e. early male emergence), differential lifespan of sexes, and differential distribution of sexes across habitat. Ten populations of A. aphidimyza were released separately in transparent cages and their sex ratio variations were recorded every 12 hours. The primary sex ratio in this species seems to be slightly male‐biased (52.41% males), however early emergence of males biases the sex ratio up to 72% males in a few hours after emergence. Shortly after the emergence of females, the sex ratio reaches its primary situation, but as a result of male‐biased mortality after mating, the proportion of females increases gradually to 97% by the fourth and fifth days after emergence. These results explicitly suggest that direct estimation of sex ratio in natural populations may be affected by some secondary factors such as differential mortality of sexes, protandry, and differential distribution of males and females over time and/or across habitat.

Does monogeny enable gall midges (Diptera: Cecidomyiidae) to regulate their sex ratio?

Monogeny, the production of unisexual broods by individual females, is widely recorded in gall midges (Diptera: Cecidomyiidae). Theoretical models propose that the adjustment of offspring sex ratio by females may pre-dispose the evolution of monogeny in gall midges however empirical studies in this field are superficial. Expressed more simply, monogeny may enable individual female gall midges to decrease or increase the number of male and female progeny they produce in response to changes in environmental conditions. Host quality/size is repeatedly reported to influence sexual investment in insects in terms of sex ratio adjustment. In this paper, we examined the sex ratio of the offspring of the monogenous predatory gall midge Aphidoletes aphidimyza attacking low and high abundances of the cotton aphid, Aphis gossypii. Two consecutive generations of female gall midges were presented with either a low or high abundance of aphids in each generation and the sex ratio of their progenies determined. There was no difference between the sex ratio of the progenies that developed on the high or low abundance of A. gossypii in the two generations. Apparently, the females did not regulate the number of female and male progenies, or adjust the numbers of male or female's eggs they produced in response to the changes in the abundance of prey. Results of this study do not support the theory of sex ratio regulation proposed for monogenous gall midges. It is likely that the skewed sex ratio in most species of monogenous gall midges is a consequence of differential mortality of male and female progenies under harsh conditions. The finding that male and female larvae did not differ in the number of aphids they require to complete their development supports this claim.

An equal sex ratio followed by differential sex mortality causes overestimation of females in gall midges: no evidence for sex ratio regulation

Monogeny, the production of unisexual broods by individual females, has been recognized for nearly 80 years. The genetic nature of gall midges' sex determination predicts an equal numbers of male-producing and female-producing females in the populations such that the overall sex ratio is expected to be nearly 1:1. However, observations of some strictly monogenous populations with biased sex ratio, mainly toward females, have raised the question of whether gall midges are able to adjust their offspring sex ratio in response to changes in environmental conditions, and some authors have even considered sex ratio regulation as a strong force in the course of the evolution of monogeny. In this paper, first, by studying the sex ratio variations of the predatory gall midge, Aphidoletes aphidimyza within a generation, we showed that adult males emerge up to 1 day earlier and have shorter life span than females (less than 4 days and up to 6 days, respectively). Although, the sex ratio of A. aphidimyza at the time of emergence was nearly 1:1 (52.41% males), a simple population simulation indicated that the differential mortality of sexes can lead to a female-biased sex ratio estimation (57.88% females) under random sampling in the natural environments. Our results imply that the primary sex ratio of monogenous gall midges is nearly 1:1 and that the arrhenogenic/thelygenic gall midges are not able to alter the number of their male/female progenies in response to changes in environmental conditions.

Evaluation of corn plant as potential banker plant for supporting predatory gall midge, Feltiella acarisuga (Diptera: Cecidomyiidae) against Tetranychus urticae (Acari: Tetranychidae) in greenhouse vegetable production

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most important and highly polyphagous pests of vegetables and other crops worldwide. Experiments were conducted in the laboratory and greenhouse to evaluate corn ( Zea mays L.) as a banker plant for the predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) to potentially control T. urticae. Choice and no-choice experiments were carried out to determine the host plant preference of an alternative prey, Oligonychus pratensis (Banks)(Acari: Tetranychidae) to corn and green bean ( Phaseolus vulgaris L.). Results showed that O. pratensis adults strongly preferred corn as a host plant and posed no risk to green bean. F. acarisuga was found to fly at least 7.0 m to search for new preys on green bean plants, and over 176 F. acarisuga larvae per leaf were recorded at 14 d after dispersal. F. acarisuga proved to be an excellent predator of both T. urticae and O. pratensis. The predation by F. acarisuga to T. urticae and O. pratensis ranged from 43.7 to 67.9% and 59.2 to 90.3%, respectively, under laboratory conditions. In a non-cage study, 81.2% of T. urticae population was suppressed by F. acarisuga in reference to the control (cage treatment). The results showed that this banker plant system has potential for controlling T. urticae in greenhouse vegetable production.

Embryogenesis of Aphidoletes aphidimyza (Diptera: Cecidomyiidae): Morphological markers for staging of living embryos

Determination of embryonic stages is an important prerequisite for the long-term cryopreservation of eggs and embryos of the predatory gall midge Aphidoletes aphidimyza. This paper describes the embryonic development of this insect based on light microscopy. Gall midge embryogenesis lasts, on average, 102 h at 17°C and 144 h at 15°C. Living embryos can be quickly separated into ten stages that are clearly defined by specific morphological markers. The necessity for selecting definite embryonic stages for cryobiological storage is discussed.

Biology, life table and predation of Feltiella acarisuga (Diptera: Cecidomyiidae) feeding on Tetranychus cinnabarinus eggs (Acari: Tetranychidae)

Abstract Feltiella acarisuga (Vallot) is a common predatory gall midge, which feeds on many species of spider mites. All major life history and life table parameters of F. acarisuga were determined using the carmine spider mite, Tetranychus cinnabarinus (Boisduval) eggs as prey under laboratory conditions [26.7 ± 2 °C, 75 ± 5% RH, and a photoperiod of l4:10 (L:D) h]. Developmental times of F. acarisuga were 2.6, 7.1, and 6.7 d for eggs, larvae, and pupae, respectively, with an average of 16.4 d from egg to adult emergence. Female immatures development took ≈1 d longer than male immatures did. Adult F. acarisuga lived an average of 12.8 d, and the female adults (13.3 d) lived significantly longer than male adults did (11.9 d). After an average of 1.5 d preoviposition period, each female laid an average of 27.3 eggs in its life span with an average of 2.1 eggs per day and an average of 2.8 eggs on each of its oviposition day. The raw data were analyzed using an age-stage, two-sex life table method that takes into consideration of the variable developmental rates among individuals and between sexes. The intrinsic rate of natural population increase (r), net reproductive rates (Ro), gross reproductive rate ( ∑ m x ) , generation time (T), and doubling time (DT), and the finite rate of increase (λ) of F. acarisuga were estimated using the age-stage, two-sex (male and female) life table analysis as 0.122 d−1, 16.19 eggs per female, 20.81 eggs per female, 22.81 d, 1.1298 d, and 5.7 d−1, respectively. Each of the first, second, and third instar larvae of F. acarisuga consumed an average of 35.5, 54.0 and 86.9 T. cinnabarinus eggs per day, respectively. Larvae of F. acarisuga could consume an average of 175.4, T. cinnabarinus eggs, and female larvae consumed 14% more spider mite eggs (187.6 eggs) than male larvae (165.1 eggs). The significance of other life table parameters related to the population and the potential of using F. acarisuga as a biological control agent are discussed.

Effects of photoperiod on induction of diapause in Feltiella acarisuga (Diptera: Cecidomyiidae)

AbstractLarvae of the predatory gall midge Feltiella acarisuga (Vallot) diapaused as prepupae in tightly woven, brown, silk cells on leaf surfaces. Photoperiod alone, at day lengths from 16 to 8 h did not induce diapause at either 20 or 25 °C. A low incidence of diapause was induced by a combined photoperiod and thermoperiod of an 8-h day at 25 °C and a 16-h night at 15 °C. The incidence of diapause was higher under these conditions if the larvae were fed diapausing spider mites, Tetranychus urticae (Koch) (Acari: Tetranychidae). Because F. acarisuga only diapauses at daylengths equivalent to mid-winter, when its prey, T. urticae, is also in diapause, it can be used as a biological control agent for T. urticae in British Columbia greenhouses throughout most of the growing season.