Solitary eumenid wasps of the genera Ancistrocerus and Euodynerus can be reared in small cages. Laboratory-reared larvae of the spruce budworm caterpillars, Choristoneura fumiferana (Lepidoptera: Torlricidae) are suitable prey

Chilcutt, Charles F

Cowan, David P

English

Valparaiso University

The Great Lakes Entomologist Volume 26 Number 1 - Spring 1993 Number 1 - Spring 1993 Article 2 April 1993 Methods for Artificial Rearing of Solitary Eumenid Wasps (Hymenoptera: Vespidae: Eumeninae) Charles F. Chilcutt Western Michigan University Kalamazoo David P. Cowan Western Michigan University Kalamazoo Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Chilcutt, Charles F. and Cowan, David P. 1993. "Methods for Artificial Rearing of Solitary Eumenid Wasps (Hymenoptera: Vespidae: Eumeninae)," The Great Lakes Entomologist, vol 26 (1) Available at: https://scholar.valpo.edu/tgle/vol26/iss1/2 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 1993 THE GREAT LAKES ENTOMOLOGIST 15 METHODS FOR ARTIFICIAL REARING OF SOLITARY EUMENID WASPS (HYMENOPTERA: VESPIDAE: EUMENINAE) Charles F. Chilcuttl ,2 and David P. Cowan l ABSTRACT Solitary eumenid wasps of the genera Ancistrocerus and Euodynerus can be reared in small cages. Laboratory-reared larvae of the spruce budworm caterpillars, Choristoneura fumiferana (Lepidoptera: Torlricidae) are suitable prey. Many problems in insect biology are difficult or impossible to study in a completely natural setting, thu  making artificial rearing methods necessary for further advances. Generally, it is necessary to provide adults with condi­tions needed for maintenance, an appropriate environment for males and females to mate, proper oviposition stimuli for females, and an adequate diet for immature stages. Fulfilling these conditions for hunting wasps is rela­tively complex because females require: (1) specific materials (from the envi­ronment) for nest construction prior t  oviposition; and (2) live arthropod prey for females to paralyze and provision for their offspring. Here we report suc­cessfully rearing, under artificial conditions, solitary eumenid wasps of the genera Euodynerus and Ancistocerus. In nature, these wasps nest in hollow twigs and vacant insect borings (Krombein 1967). Within a cavity, a female lays an egg; she then hu ts for and paralyzes caterpillars that are placed within the cavity or nest near her egg. When enough prey items have been placed in the cavity with e egg, the female then makes ud by mixing water and dry soil. She uses thi  mud to seal off a cell that contains her egg and its provisions. This process may be repeated in the same nesting cavity until it is filled with a linear series of cells containing her offspring. Observations by Steiner (1983) and by Vee endaal and Piek (1988) indicate that female eumenid wasps will engage in predatory and nesting behaviors within the confines of small cages. Such behavior makes large-scale artificial rearings possible. MATERIALS AND METHODS Eumenid wasps were obtained by rearing them from trap nests placed out in Kalamazoo and Ir n counties, Michigan. Wasps were either removed from trap nests as larvae, or captured as young adults as they emerged from their nests. Males were transferred to a holding cage upon emergence, and two day lDepartment of Biological Sciences, Western Michigan University Kalamazoo, MI 4900~. Current address: Department of Entomology, University of Hawaii. 3050 Maile Way. Honolulu. HI 96822. 1Chilcutt and Cowan: Methods for Artificial Rearing of Solitary Eumenid Wasps (HymenopPublished by ValpoScholar, 199316 THE GREAT LAKES ENTOMOLOGIST Vol. 26, No.1 post-emergence females were placed in the cage with the males (different ages) for mating. Both mated and unmated females were used in this study. Captive rearings were carried out on the Western Michigan University campus during the summers of 1989-1991. Rearing cages were placed in a courtyard surrounded by a 3 story building. This allowed natural weather phenomena, but decreased sun exposure in the morning and evening. We reared wasps in 60 cm X 60 em X 60 em cages constructed of plywood bottoms, with one side and top of glass, and three sides of aluminum screen (18X16 mesh). For access, a 15cm square hole in t e comer of a screened side supported a 100cm long cloth sleeve that could be knotted. I  1989, cages were raised 4cm above the ground on boards to p event rotting. In 1990 and 1991, cages were placed on wooden stands (60cm high), with tangle foot applied to th  legs to keep out pests. All outdoor cages contained: (1) a petri dish supplied daily with sugar water, (2) a jar lid of dried clayey mud, and (3) a petri dish supplied daily with water. A microscope slide was placed inside th water dish to allow wasps that fell in the water (a frequent occurrence) a  escape route. Generally, the sugar water dried quickly: however, the wasps moistened the crystals with water and ate. Two or four females were placed in each cage, with each cage provided with two nes s per wasp, wired to the inside screen or placed on the cage floor. The hole diameters of the nest sticks were the same as the sizes they selected in nature (5.6 mm, 6.4 mm, and 7.1 mm). The day after a nest was completed, as evidenced by a mud plug in the nest-hole entrance, the est was removed and another nest was provided in its place. To provide wasps with potential prey, diapausing first instars of the spruce budworm, Choristoneura fumiferana (Clemens) were obtained from the Canadian National Forestry Laboratory in Sault Ste. Marie, Ontario, and reared on commercial (Bioserve Corporation) diet, following instructions in Grisdale (1984). Collins and Jennings (1987) found spruce budworms to be a common prey (94% of prey found in trap nests) of Euodynerus and Ancistro­cerus species in a spruce-fir forest. By placing budworms on the diet at the time of first-male emergence, prey items of suitable size (> 2mm) were avail­able when female wasps began hunting about 10 days later. As an alternative to the commercial diet, we reared some budworms on a diet of tender buds of white spruce, Picea glauca. Expanding buds were cut early in the growing season and frozen for later use. For rearing budworm larvae, buds were thawed, sprayed with the same fungicide used with the artificial diet, and then placed in 30ml plastic cups. Attempts to rear bud­worms on mature spruce foliage were unsuccessful. In 1989, 17 adult female Euodyn rus foraminatus (Saussure), and one female Parancistrocerus sp. were placed in outdoor cages, with one cage con­taining four wasps and seven cages containing two wasps apiece, nd observed from 23 June until 1 August. In 1990, 18 Euodynerus planitarsis (Bohart) and 8 E. foraminatus were placed in outdoor cages (six cages con­tained three E. planitarsis apiece and two cages containing 4 E. foraminatus apiece) on 15 June and observed until 21 September.In 1991,13 E. planitarsis, 2 E. foraminatus, 2 Euodynerus hidalgo (Saussure) and 4 Ancistrocerus antil­ope (Panzer) females were placed in outdoor cages on 1 June and observed until 30 September. Indoor rearings were attempted in 1991. Five E. foraminatus females were placed singly in pint jars; four were placed singly in gallon jars. Each jar contained two trap nests, a capful of mud, a capful of water, and white spruce shoots. Jar openings were covered with screening and the wasps were fed on honey smeared on this cover. Honey or sugar water provided needed carbohy­2The Great Lakes Entomologist, Vol. 26, No. 1 [1993], Art. 2https://scholar.valpo.edu/tgle/vol26/iss1/21993 THE GREAT LAKES ENTOMOlOGIST 17 drates for the wasps. Due to limited space in the jars, prey were removed from rearing cups and placed on th  spruce in the jars. RESULTS AND DISCUSSION During 1989, all 17 female wasps entered nest sticks; however only 3 E. foraminatus hunted, captured prey, and provisioned nests. Beginning on 7 June, these 3 females completed eleven nests that produced adult offspring, 10 females and 9 males During 1990, all 14 E. planitarsis females nested beginning on 30 June. They completed 59 nests that contained 127 provisioned cells, which produced 84 adults. Five of the 8 E. foraminatus females nested and completed 11 nests that contained 46 provisioned cells and which produced 35 adults. All of he offspring reared in 1990 were adult males, indicating that none of the parentfemales had mated. We reared parental females from larvae placed in vials, and transferred the newly emerged adults to cages with males for a day. We then transferred th  females into the rearing cages that contained nesting supplies. Apparently the females were not fully mature and ready to mate when placed in the cage with t e males. We avoided this problem in 1989 a d 1991 by leaving larvae and pupae in their ests and allowing them to trans­form to adults and emerge on their own. One day later we placed them in cages with males and watched to be sure they mated. In 1991, the first wasp began nesting in the cages on 7 June, apparently early due to unseasonably warm weather. ThirteenE. planitarsis completed 41 nests which contained 70 provisioned cells. One of 2 E. foraminatus females completed 2 nests with 3 provisioned cells. One of 4 A. antilope females com­pleted 2 nests on the same day, each with one provisioned cell, before escaping from the cage. 1\vo of the 3 A. antilope that did not nest captured prey without placing them in a nest stick. The E. hidalgo females showed no inter­est in prey, never displaying huntinf5 or searching behaviors. Attempts to rear wasps indoors In jars were less successful. Although 6 of the 9 wasps began nesting, mortality of the females was high. The primary problem was obtaining a b8.1ance between proper light and temperature condi­tions. Wasps tended to remain in their nest under artificial . g (fluores­cent) or when placed in naturally lit areas but not in direct su t. If placed in direct sunlight on warm days, temperatures in the jars soared and wasps died. Placing the jars in direct sunlight with partial shade seemed to help. Nests taken from the jars were damp, and most contained fungal growth. Apparently the heat and water provided for the wasps increased the humidity above safe levels. This problem did not occur outdoors in the better ventilated screen cages. In cramped rearing containers, caterpillars often crawled behind objects where the wasps could ot reach. Spruce twigs placed in the rearing jars provided a centralized hunting area where budworms tended o stay. During the normal process of getting water and mud and returning to the nest to build mud partitions, several wasps were seen chewing on the caterpil­lars' silk and possibly their frass. Perhaps wasps were using something from these materials as additives to the mud partition. All observed wasps spent time searching over the mud provided them before collecting mud from a well chosen spot. Such behaviors indicate th  selection of the right kind of mud (apparently cohesive enough for t e wasp to mold) is important. The low nesting success in 1989 (only 3 wasps nested) apparently was due to ants and earwigs (Forficula sp.) getting into the cages. Cages placed on boards near the ground were accessible to small insects that could get through 3Chilcutt and Cowan: Methods for Artificial Rearing of Solitary Eumenid Wasps (HymenopPublished by ValpoScholar, 199318 THE GREAT LAKES ENTOMOLOGIST Vol. 26, No.1 cracks or the screen mesh. Earwigs entered the cages by crawling into the cage sleeve and falling into the cage when t  sleeve was used. We later discovered (while opening nests) that earwigs sheltered in the nests, and pos­sibly deterred wasps f om nesting. However, several wasps barricaded ear­wigs in the e ds of the nests with mud partitions. Three of 4 nests found this way successfully produced offspring. Ants were the most notable pest prob­lem, because they competed with he wasps for budworm prey. Ants killed and dismembered budworms to remove them through the screen. When ants came upon wasps holding prey (which the wasps often do while waiting for the venom to work, the ants would grab onto the caterpillar and a tug-of-war ensued. The ants always came out the victor (observed > 20 times). In 1989, the cages were placed in an are  where they were shad d during the warmer hours of the day (1200 to 1400 h), because we believed that direct sunlight would heat the cages to a deadly temperature. However, th  limited nesting success of these wasps rompted us to place the cages in the open (i.e. direct sunlight all day) for subsequent studies in 1990 and 1991. Cut evergreen branches were placed on the tops of cages, thus creating shaded and unny areas within each cage during th  day. Only when air temperature exceeded 35° C were wasps observed resting for periods in the shade. One problem encountered by placing the cages in dir ct sunlight was high spruce budworm mortality. This problem was solved by placing the rearing cups that contained budworm larvae in the area of the cage shaded during mid-day. Our increased success in rearing wasps after 1989, mainly was due toplacing the cages on stands with tanglefoot around the legs. Such barriers eliminated all ants and earwigs from the cages, lthough we still removed an occasional spider. At no time during the rearing studies did we find n st parasites or parasitoids of either wasps or spruce budworms. Hence, we con­clude that the increased nesting success from 18% of wasps in the total sample which layed eggs in 1989 to 63% in 1990 primarily was do to exclusion of ants which significantly impact solitary wasps' nesting success. Mortality of E. planitarsis and E. foraminatus immatures reared in 1990 was only 31.2% compared to 45.3% for eumenids observed in nature (Cowan 1981). This difference (14.1 %) is attributable to the absence of nest parasit s, parasitoids, and predators. Most of the wasp mortality during our study (> 60%) resulted from our clumsy handling of nests which caused injury to unhatched eggs or delicate mmature wasps. Fungi and other unknown patho­gens contribute to the remainder of the mortality. We found the following factors most important for successful propagation of wasps: (1) Insure that female wasps have successfully mated; otherwise, only male offspring will result. (2) Supply adequate nesting resources i.e., nest sticks, carbohydrates (sugar or honey), water at all times, dried mud with adequate clay content, and potential prey larvae. (3) Daily exposure to sun­light, with partial shade to avoid overheating, is needed; also, adequate venti­lation to c trol humidity. (4) Measures to exclude pests such as ants improve nesting success. LITERATURE CITED Collins, J.A., and D.T. Jennings. 1987. Nesting height preferences of eumenid wasps (Hymenoptera: Eumenidae) th t prey on spruce budworm (Lepidoptera: Tortricidae). Ann. EntomoL Soc. Am. 80: 435-438. Cowan, D.P. 1981. Parental investment in two solitary wasps Ancistrocerus adiabatus and Euodynerus foraminatus (Eumenidae: Hymenoptera). Behav. Ecol. SociobioL 9:95-102. Grisdale, D.G. 1984. A laboratory method of mass rearing the eastern spruce budworm 4The Great Lakes Entomologist, Vol. 26, No. 1 [1993], Art. 2https://scholar.valpo.edu/tgle/vol26/iss1/21993 THE GREAT LAKES ENTOMOLOGIST 19 Choristoneura fumiferana. In: E.G. King. and N.C. Leppla (eds.j. Advances and chal­lenges in insect rearing. U.S. Dept. Agric. Tech. Bull. pp. 223-231. Krombein. K.V. 1967. Trap-nesting Wasps and Bees: Life Histories. Nests. and Associ­ates. Smithsonian Press, Washington, D.C. Steiner, A.L. 1983. Predatory behavior of solitary wasps V. Stinging of caterpillars by Euodynerus foraminatus (Hymenoptera: Eumenidae). BioI. Behav. 8:11-26. Veenendaal. R.L., and T. Piek. 1988. Predatory behaviour of Disc elius zonalis (Hyme­noptera: Eumenidae). Entomol. Ber. (Amsterdam) 48:8-12. 5Chilcutt and Cowan: Methods for Artificial Rearing of Solitary Eumenid Wasps (HymenopPublished by ValpoScholar, 1993

Methods for Artificial Rearing of Solitary Eumenid Wasps (Hymenoptera: Vespidae: Eumeninae)

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Methods for Artificial Rearing of Solitary Eumenid Wasps (Hymenoptera: Vespidae: Eumeninae)

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