Collecting Chalcidoidea: Why and How
Purpose of this Page:
1) Provide introductory information on Chalcidoidea and how to collect them to amateurs and novices that are/may become interested in pursuing them.
2) Survey some of the less-expensive equipment and techniques commonly utilized
in collecting Chalcidoidea (references with more comprehensive information are
A. Introduction to Chalcidoidea:
A. Introduction to Chalcidoidea:
Chalcidoidea includes 19 families of parasitic hymenopterans that range in size from 0.1 mm to 45 mm, often with bright metallic coloration and intricate sculpture. These wasps parasitize (rarely predate) a wide variety of immature arthropods: 13 orders of Insecta, two orders of Arachnida and one family of Nematoda (Grissel & Schauff 1997). Six families of Chalcidoidea are completely or partially phytophagous being gall formers, seed eaters, and inquilines in other galls or stem borers.
Members of Chalcidoidea are cosmopolitan in distribution and habitat utilization (See below). They have been used widely in successful biological control programs of insect pests with 4 of the 6 most successful hymenopteran families utilized belonging to Chalcidoidea (Noyes & Hayat 1994). Despite the diversity and abundance of Chalcidoidea, their small size and the limited number of workers in Chalcidoidea have precluded the accumulation of a large knowledge base on the lifestyles of these wasps. Noyes (1998) regards 2,040 genera and 21, 250 species as valid. This encompasses a third of the described parasitic Hymenoptera (second only to Ichneumonoidea (LaSalle & Gauld 1991)) and Gordh (1975) predicted that, ultimately, Chalcidoidea would prove to be the largest superfamily. Noyes (2000) went a step further in predicting that over 400,000 species might in fact exist.
B. Characterizing Chalcidoidea:
Chalcidoidea is characterized by highly reduced forewing venation consisting of (at most) a single vein complex subdivided into submarginal, marginal, postmarginal and stigmal veins (Chalcid wing). Chalcidoids are the only apocritans possessing an independent, externally visible, mesopleural sclerite - the prepectus (Gibson 1985) (Prepectus). The prepectus separates the mesopleuron from the pronotum, often resulting in the failure of the pronotum to contact the tegula. The mesothoracic spiracle, if evident, is located at the dorsal margin of the pronotum, near the pronotal/prepectal juncture. Finally, most chalcidoids possess multiporous plate sensilla on the flagellar segments that usually project above and beyond each segment (sensilla).
C. Biology and Behavior:
As alluded to in Section A, chalcidoids are incredibly diverse biologically in that they exhibit all 15 of the feeding types described by Hagen (1964) for insects except two (Grissell & Schauff 1997). This is one of the widest host ranges known for any group of insects. So far as is known, at least 13 orders of Insecta are attacked as well as ixodid ticks, gall-forming mites, spider egg sacs (Grissell & Schauff 1997), and garypid pseudoscorpion cocoons. Despite the paucity of information in general, phenomenal behaviors have been documented for several taxa, for example: Lasiochalcidia spp. (Chalcididae), an ant lion parasite that leaps into the jaws of death; Chalcis canadensis (Cresson) (Chalcididae), which "stands up" while ovipositing; and Trichogrammatids, Podagrion (Trichogrammatidae, Torymidae), which hitch a ride (phoresy) on hosts whose eggs they parasitize.
D. Collecting Chalcidoidea:
Why have only about 4% of the 400,000 estimated species been described?
Firstly, there are relatively few qualified taxonomists/systematists working on this group. Secondly, only a select few actually collect with the specific intent of capturing Chalcidoidea. This may be due, in part (and partly true), to the perception that Chalcidoidea is a ‘difficult’ group to work on given their small size (usually <2 mm in length), limited and plastic morphological features, and that "specialized" collection/curation techniques are required for proper acquisition and preservation. However, these insects can be collected and/or reared with a minimal monetary investment and fairly general techniques.
The low interest in collecting Chalcidoidea can be attributed to the apparency and intent of a particular collector. To the generalist collector sweeping in the field, the apparency of these hymenopterans is going to be limited to those that don’t escape through the large holes in the net bag of a conventional butterfly net. Further, most generalist collectors don’t go out in search of minute wasps specifically; rather they are a by-product of incidental collection in sweep, vacuum or Berlese samples. As such, once larger and/or target taxa are removed, any Chalcidoidea collected are typically discarded. Further, given their small size and often delicate sculpture, they will tend to collapse unless properly handled.
E. Collection Techniques:
E. Collection Techniques:
The basic equipment required to collect these insects is a fine-mesh net, aspirator and receptacle for specimens (usually vials of alcohol or Zip-Loc™ Bags with salt slurry). This is all that is needed in order to sample Chalcidoidea in an effective manner. Of course, many modifications to basic techniques and specialized techniques have been developed over the years. We will try to touch on a few of these. For general insect collecting techniques and elaboration on certain methods listed here, see (Collecting).
What to bring…
1. aspirators (standard form, above;
straight tube form, below)
2. aspirator vials
4. spare straight tube aspirator tube
5. Nalgene bottle
6. killing tubes
7. vials of alcohol
9. writing implements
11. pan traps
12. magnifying lens, & loupe
1. Aspirators useful for collecting Chalcidoidea come in two forms: the simple, straight tube and the standard form with attached collection vessel. Both pictured have inexpensive Volkswagon fuel filters to remove debris from the airstream that could be inhaled. The straight tube is a glass or plastic tube attached to flexible surgical tubing. Fine screen epoxied inside the glass tube captures small insects that can then be blown into alcohol or salt slurry. The standard aspirator collects insects into a vial which allows for a longer time between emptying the catch (compared to straight tube). The model pictured has an elongated brass tube for reaching deep inside the net (produced by Rose Entomology).
2. Useful to have in the event of breakage or the collection of numerous individual samples.
3. Repellent is optional. Local conditions and personal preferences dictate its use.
4. An extra prepared straight tube is handy in the event of breakage or cracking of the original tube.
5. Small, screw-top Nalgene™ bottles are convenient if additional alcohol or ethyl acetate are brought along.
6. Killing tubes are useful for larger hymenopterans (including some Chalcidoidea) that are too large to aspirate. Ethyl acetate or acetone (many nail polish removers) is probably the safest and easiest to acquire killing agent for charging tubes.
7. 70% ethyl alcohol (ethanol) is preferred for dispatching aspirated Chalcidoidea, although isopropyl alcohol can be used in a pinch. Leak-proof, screw top glass vials are best for storing individual samples, but plastic Whirl-pack bags (See Bioquip for both) are also useful in some instances.
8. Forceps are useful for manipulating small insects that become lodged in tight spaces during transfers to and from killing to storage receptacles or re-capturing stunned escapees. Fine tip flexible and non-flexible forceps each have their uses though are not required.
9. Alcohol and/or waterproof pens and pencils are essential for recording field observations, host identifications and collecting locality information. Excellent fine-tip ink pens include Sharpies, Pigma Microns, and Staedtler Pigment Liners while inexpensive mechanical pencils never require sharpening.
10. Syringes are optional. They are useful for injecting large moths with alcohol to prevent them from wildly flapping inside killing tubes and coating everything with scales. Typically, if one collects moths/butterflies, they should have a killing tube dedicated to them.
11. Yellow pan traps are an inexpensive and simple means of passively sampling microhymenoptera in an area. Solo brand bowls work wonderfully. Each bowl is filled with water mixed with a small amount of liquid detergent to decrease the surface tension of the water. Traps must be emptied every 1-2 days to prevent specimen deterioration. They can be checked every 3-4 days if a saturated salt solution is used in place of plain water. All pans from a given area can be poured through a fine aquarium net to collect the specimens. The decanted solution can be poured into a yellow pan trap for re-use. Salt and detergent levels should be checked to determine if re-charging is required, particularly if it has rained recently. The aquarium net can be everted into a whirl-pack or Zip-Loc Snack bag. Specimens should be rinsed before storing in alcohol. Although more labor-intensive, this technique is well-suited for use in nearby woodlots, ditches or meadows that can be accessed easily and frequently (See Below).
12. A small magnifying glass is optional and allows one to examine specimens in the field.
13. collecting equipment box
14. anemometer/thermometer (optional)
15. field notebook
16. Zip-Locks and paper bags
17. Glassine envelopes
13. We use a plastic Plano tackle box with snap down lid for most of our supplies listed on this page. It is lightweight, stackable and allows me to simply grab it and go without worrying if some component was missed.
14. Optional and expensive "toy" for you weather nuts. This is fun to use in the field, but doesn’t enhance insect collecting efficacy.
15. A simple field notebook is compulsory. They range in price from inexpensive $1.00 spiral pocket notebooks to $15.00 weather-resistant, bound "books". Always enter observation/locality information in pencil or waterproof ink in case of inclement weather.
16-17. Large Zip-Loc™ Bags, glassine envelopes, and small-medium brown paper bags are great if you are collecting potentially parasitized host material for rearing or host plant samples for identification. Placing plant samples or live insect host samples inside the paper/glassine bags (LABEL them!!) inside the Zip-Locs retards sample dessication and formation of condensation inside the plastic bag. Samples so packaged can be maintained for 3-4 days on ice or in the refrigerator. See below for a brief treatment of what and how to rear parasitic Hymenoptera and references providing more detail.
NOT FIGURED: GPS unit to provide detailed information on exact location for your notes, labels, etc.
Where to go…
|Grassland||Mountain Meadow||Desert Sand Dunes|
The photographs above represent three disparate habitats where Chalcidoidea are commonly found. Sometimes the best spot to collect is not in some exotic, distant locale but rather locally. Local areas are advantageous in that they can be sampled consistently over longer periods of time and do not require extensive outlays of cash and time as would extended trips. We have had incredible success in what appeared to be "crummy" habitat like drainage ditches along roadsides and overgrown, weedy lots. Such disturbed sites can provide a wealth of interesting taxa, despite untoward appearances.
Productive areas within a particular habitat may include blooming plants (particularly those with small flowers), spring or seepage areas with lush vegetative growth, or plants infested with insects that produce honeydew (e.g. aphids, mealybugs, scales, etc.). These areas all have a common element: there is something there that the chalcidoids "want", be it nectar, honeydew or hosts to parasitize.
How to collect...
Two effective methods commonly employed are sweeping and rearing. Extraordinary detail into both methods will not be provided here as they have been dealt with completely elsewhere (see references). However, we will cover the basics necessary to begin a productive collecting adventure.
Sweeping: Generally, a fine mesh or muslin net bag is sufficient for sampling Chalcidoidea. The net is swept across vegetation from low-growing grasses up to tree canopies. For enhanced information content with respect to potential host associations, try sweeping from a particular known plant species initially then switching to an alternate plant species in the area after thoroughly sampling the initial plant selected. As material accumulates, a bolus will form at the bottom of the net bag. This is pinched off and minute parasitic Hymenoptera may then be aspirated as they separate themselves from the bolus of plant parts. They appear as small, often saltatory, yellow, black or brown specks walking and flying about. Since the majority of Chalcidoidea are attracted to light, it is best to position the net bag so that sunlight shines through the top of the net rather than into the net opening. Alternatively, the bolus may be placed into an alcohol container (bag) for later processing. Note: if using an aspirator with a chamber, avoid aspirating spiders as they usually produce webbing that interferes with specimen transfer and subsequent sorting. Sometimes they will attack your catch!
Rearing: This is typically the most labor-intensive (but also potentially the most rewarding) form of obtaining Chalcidoidea. It is advantageous not only in that host associations and habitat requirements of the parasitoid can be identified, but also male and female associations may be postulated, something often difficult to do definitively with sexually dimorphic taxa which are collected by sweeping. Obvious things to collect for rearing are galls, leafmines, egg masses, scales and mealybugs, while not so apparent things might be seeds, flower heads, acorns, stems, etc. Any type of clear container will enable daily checking of materials for emergence.
Passive Sampling: The only technique treated here is pan trapping (see "What to bring" above) although numerous additional techniques exist (malaise trapping, flight intercept traps, pitfall trapping, etc.). For pan trapping, Yellow Solo Bowls are placed in areas of the habitat which are likely to be productive for Chalcidoidea (near flowers or insect infestations, under shrubs or near seeps, etc.). The bowls are then filled with a saturated salt solution or water (salt solution when emptying every 3-4 days or water when emptying 1-2 days) and 1-2 drops of liquid soap are mixed in to reduce the surface tension of the water. Many smaller insects will be attracted to the yellow color and collect in the bowl. A small aquarium net is perfect for straining the catch which can then be easily rinsed to remove salt/soap residue and inverted into bag or vial of ethanol. Traps should be placed where they are likely to remain undisturbed by humans or weather phenomena (rising water, flooding).
Many of the other techniques listed above require a more intensive time and monetary investment and are treated in the references listed below.
Gibson, G. 1985. Some pro- and mesothoracic structures important for phylogenetic analysis of Hymenoptera, with a review of some terms used for structures. Canadian Entomologist 117: 1395-1443.
Grissell, E. & M. Schauff. 1997. Chalcidoidea, pp. 45-116. In Gibson, G., Huber, J., & J. Wooley [eds.], Annotated Keys to the Genera of Nearctic Chalcidoidea (Hymenoptera). NRC Research Press, 1997.
Gordh, G. 1975. Some evolutionary trends in the Chalcidoidea (Hymenoptera) with particular reference to host preference. Journal New York Entomological Society 83: 279-280.
Hagen, K. 1964. Developmental stages of parasites. pp. 168-246. In DeBach, P. [ed.], Biological Control of Insect Pests and Weeds. Chapman & Hall, London. 844 pp.
LaSalle, J. & I. Gauld, 1991. Parasitic Hymenoptera and the biodiversity crisis. Redia 74: 315-334.
Noyes, J. 1982. Collecting and preserving chalcid wasps. Journal of Natural History 16: 315-334.
Noyes, J. 2000. The Encyrtidae of Costa Rica. Memoirs of the American Entomological Institute 62: 355 pp.
Noyes & Hayat, 1984. A review of the genera of Indo-Pacific Encyrtidae. Bulletin of the British Museum (Natural History), Entomology Series 48(3): 395.
Schauff, M. Collecting and preserving insects and mites: techniques and tools. http://www.sel.barc.usda.gov/selhome/collpres/collpres.htm
Bioquip Products, 17803 LaSalle Ave., Gardena, CA 90248-3602. Telephone: (310) 324-0620. E-mail: email@example.com. Web: www.bioquip.com. Equipment for collecting, processing and storing arthropods, texts, etc.
Rose Entomology, 17344 Eucalyptus, Unit B3, Hesperia, CA. Tel & Fax: Local: (760) 244-7324 Toll Free: (877) 249-1623 Web: www.roseentomolgy.com. High quality collecting equipment including nets, light set-ups, aspirators, etc.
The use of trade, firm, or corporation names on this page is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the United States Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable.