Localized geographic areas often have unusual or unique structural pest situations which are endemic to such areas. Unless one has a broad knowledge of entomology, these pest situations are likely to become extremely puzzling and bothersome. Troubling encounters with unusual pests are compounded by the fact that structural pest control reference books quite often do not contain any information on these pests.
It should be pointed out that unusual pest occurrences are cyclical in nature. They may suddenly appear in one year, only to disappear and not recur again for some time.
In this article, information is presented on three unusual pest situations which were encountered last year in Southern California.
CASE #1. On Feb. 5, 1996, a termite inspector requested that a determination be made on a piece of 2 x 4 lumber which was of concern to a homeowner. This wood was a load-bearing element of a children's swingset located in the backyard of a home in Upland, Calif. The inspector claimed that upon observing the wood in situ, he noticed small black and yellow insects entering holes in the wood. Unfortunately, no specimen was captured for identification purposes.
Examination of the wood revealed that it was damaged by wood decay fungi. Further dissection revealed wood-boring beetle tunnels loosely packed with frass. In many of these abandoned beetle burrows, groups of small syrphid flies were present. The number of flies in these aggregations ranged from six to 10. Three live larvae were recovered from the beetle burrow systems. These were identified by the author as immature Hymenopterans. These discoveries led to the following questions:
(1) What are groups of small syrphid flies doing in abandoned beetle burrows?
(2) What are immature Hymenopterans doing in vacated wood-boring beetle galleries?
In order to obtain answers to these questions, the remaining portions of the wood were cut into smaller pieces, placed in an insect rearing cage and held at room temperature for possible insect emergence. Shortly thereafter, several small Crabronine wasps (Hymenoptera: Sphecidae) emerged from the wood. Further research revealed that these wasps belonged to the genus Ectemnius.
The genus Ectemnius consists of 160 described species which are cosmopolitan in distribution (Bohart and Menke, 1976). Michener (1971) reported that wasps of the genus Ectemnius make their nests in rotting stumps and logs of oak, sycamore, and elm. They can make their own burrow systems in decayed wood or they will utilize old beetle burrows as nesting sites. Their burrows were complicated with as many as 24 branches, each ending in a cell which was provisioned with 2 to 16 prey. There can be as many as 16 cells per nest. Ectemnius nest cells were reported to be provisioned with syrphid flies (Michener, 1971). Bohart and Menke (1976) reported that adult flies were the favorite prey of wasps of the genus Ectemnius.
The wasps reared out in this study averaged about 1 centimeter in length. They were black in color with five yellow bands across the dorsum of the abdominal segments. The tibia and tarsus of all the legs were yellow in color.
A search of the literature revealed that this is the first report of an Ectemnius species nesting in construction-grade lumber.
CASE #2. In May, June and July 1996, pest control technicians servicing the cities of Rancho Cucamonga, Walnut, Diamond Bar, Alta Loma, Ontario, Chino, Hemet and Chino Hill, Calif., began reporting piles of dirt with large holes in the center appearing in flower beds and next to concrete walkways and driveways, etc. on residential accounts they were servicing (Figure 1). Customers and technicians described these workings as rattlesnake holes, tarantula holes, Jerusalem cricket burrows, giant earthworm castings, termite workings, gopher and/or mole activities, etc. I did not pay much attention to these reports until two of these workings suddenly appeared overnight adjacent to walkways in my front yard in Ontario, Calif. As I was not too familiar with these workings, I set out to try to solve the mystery.
Persistent observation revealed that these burrows were being utilized by wasps. Upon returning to the burrows these wasps would plunge directly into the nest entrances, allowing only a few seconds of fleeting observations. In order to capture specimens for identification, I waited until a wasp entered its burrow and then I inverted a 1-pint mason jar over the nest. Upon emerging from the nest, the wasp became trapped in the jar. A total of eight specimens were captured in this manner from locations in Ontario and Rancho Cucamonga.
The captured specimens were identified by the author as members of the genus Tachytes (Hymenoptera: Sphecidae: Larrinae). The genus Tachytes consists of more than 250 species which are nearly worldwide in distribution. All species nest on the ground and provision their nests with Orthoptera, primarily of the families Acrididae and Tettigoniidae (Bohart and Menke, 1976; Evans and Kurczewshi, 1996).
The Tachytes captured in this study were large wasps measuring about 1.8 to 1.9 centimeters in length (Figure 2). They possessed large, green compound eyes. The femur, tibia and tarsus of all their legs were reddish in color. The distal portions of the dorsum of the first three abdominal segments were covered with short, shiny, appressed hairs which gave them a banded appearance.
Ten burrows of Tachytes were observed in flower beds of a commercial building in Rancho Cucamonga, Calif., on July 18, 1996. Virtually all of these excavations were near the edges of the concrete in the corners of flower beds (Figure 1, above). Four burrows were located in expansion joints at the curb/sidewalk junction (Figure 3).
The amount of soil excavation by these wasps in the fine sandy soils at the Rancho Cucamonga location was certainly impressive. One excavated dirt pile was 9.5 centi-meters high and 10 centimeters wide at the base. These excavated dirt piles were conical in shape with a perfectly round hole measuring from 1.1 to 1.2 centimeters in diameter located in the center.
CASE #3. During the past 19 years of structural pest control work in Southern California, I have occasionally encountered Megachilid bees (Hymenoptera: Mega-chilidae) nesting in or on structures. The Megachilidae is one of the largest families of bees. The largest of its two subfamilies, the Megachilinae, comprises more than 630 North American species.
Bees of this family are solitary insects which are commonly called leaf cutting bees and mason bees. They often nest in holes in wood, in hollow stems of plants, and in burrows or cavities in masonry and in soil. Sometimes these bees may make use of abandoned nests of other bees or wasps as nesting sites (Figure 4) (Hurd and Michener, 1955). Their nests are lined with oval or circular plant materials often cut from leaves of roses and flower petals. The cells are usually placed end to end in a series separated and provisioned with a nectar-pollen paste. The females of the nonparasitic species of Megachilidae can be identified easily by the presence of pollen-collecting hairs, or scopa, which are located on the underside of the metasoma.
Most Megachilidae bees are important pollinators of native flora and crop plants (Bohart, 1972). They are of great benefit to man because of their pollination services. The minor damage they may cause by cutting leaves and petals of flowers and occasionally nesting in or on structures is far outweighed by the great good they do in pollinating flowers (Essig, 1958).
Figure 4 shows an abandoned Polistes wasp nest which was taken from the eave of a house located in Covina. Calif., on June 12, 1996. This wasp nest was being utilized as a nesting site by Megachilid bees as evidenced by the presence of plant materials in some of the cells. The red and purple materials in some of these nest cells appear to be from bracts of flowers of Bougainvillaea. The other yellow materials appear to be from petals of roses.
CONCLUSIONS. Structural pest control operators (PCOs) are frequently called upon by homeowners to shed some light on pest situations in and around structures. Sometimes these situations are quite unusual and they go beyond the scope of a PCO's usual and normal business activities. How should these situations be handled? Curiosity should motivate a PCO to try and obtain answers to these unusual pest situations. As true professionals, we must constantly seek to expand our knowledge base, for it is this knowledge base that allows us to grow, flourish and become better at what we do.
Here in Southern California, many structural PCOs have come up with a nice, convenient way to explain away almost all pest situations outside of structures with which they are not familiar. They simply tell a customer: "That's an agricultural pest, we don't control those." That may be an easy way out of an uncomfortable situation, but in an era when pest control companies are desperately trying to differentiate themselves from their competitors, the easy way out is not the smart way out.
By showing some concern and interest in what the customer is troubled about, one can greatly increase one's credibility with that customer. If you do not know the answer, it will serve you well to try to find a competent person who can help. By going the extra mile for a customer, a PCO can create a customer for life.
In the future, structural pest control operators will need to have greater knowledge of many types of pests and pest situations than they had in the past to survive in a highly competitive marketplace.
Customers are demanding more and more from PCOs. Integrated structural pest control in the new millennium will be a business of science rather than a pesticide or pest business. Pest management professionals who still cling to the belief that they do not have to know what it is to kill it with a broad spectrum pesticide are a vanishing species, and they are most certainly going to go the way of the dinosaurs.
The author is an urban and structural entomologist with Terminix International, Rancho Cucamonga, Calif.
REFERENCES
Bohart, G.E. 1972. Management of wild bees for the pollination of crops. Ann. Rev. Entomol. 17:287-312.
Bohart, R.M. and A.S. Menke. 1976. Sphecid Wasps of the World: A Generic Revision. Univ. of Calif. Press, Berkeley, Calif. 695 pp.
Essig, E.O. 1958. Insects and Mites of Western North America. The Macmillan Company, New York. 1050 pp.
Evans, H.E. and F.E. Kurczewshi. 1966.
Observations on the nesting behavior of some species of Tachytes (Hymenoptera: Sphecidae, Larrinae). Kansas Ent. Soc. Jour. 39:323-332.
Hurd, P.D. and C.D. Michener. 1955. The Megachiline bees of California. (Hymenoptera: Megachilidae). Bull. Cal. Insect Survey 3:1-247.
Michener, C.D. 1971. Notes on Crabonine wasp nests. Kansas Ent. Soc. Jour. 44:405-407.