Identification and Habits of Key Pests of Washington {Workers and Winged Reproductives) COVER PHOTO (R.D. Akre): worker. Note that thoracic profile is evenly convex; no notch (see text). ROGER D. AKRE, Professor and Entomologist, and ARTHUR L. ANTONELLI, Extension Entomologist

Ants (: Formicidae) are an easily between queens and workers and can be recogniz­ recognized group of social . The workers are ed by ocelli (simple "eyes") on top of the head, wings, wingless, all possess elbowed antennae, and all protruding genitalia, and large eyes. The sole func­ have a petiole (narrow constriction) of one or two tion of the male is to mate with a queen. segments between the thorax and the abdomen. The queen is the largest member of the colony. She One of our most common and abundant insects, a has wings but loses them soon after mating. How­ 1990 count revealed 8,800 species of had been ever, scars where the wings were attached remain. described, and there are still a number of undescrib­ Queens usually also have ocelli, in addition to large ed species in the world. The true number probably eyes, and a large abdomen for egg production. lies between 12,000 and 14,000. The worker, the smallest member of the colony, Ants are also one of the most widely distributed of lacks ocelli (usually) and is never winged. Workers all groups. They occur from arctic tree line to may be of one size (monomorphic) or may vary con­ the humid tropics, from Alaska to the extreme tip of siderably in size (polymorphic). Large workers are South America, to the tip of Africa, Australia, and usually called soldiers or majors; very small workers even to all the islands in the oceans. They are the are minors. most abundant of all social insects. Ants pass through several distinct developmental Since there are so many species of ants, and in such stages in the colony: egg, larva, pupa, and adult. The diverse habitats, it becomes obvious that ants are egg is very small and varies in shape according to one of man's principal insect competitors. Ants in­ the species. The larva also varies in size and shape, fest buildings as a nuisance, feed on human foods, but is usually white and is always legless. The pupal and even cause structural damage to buildings. stage looks like the adult, but is soft, white, and motionless. Many are enclosed in a cocoon of a Ants are also annoying because of their biting or brownish or whitish, papery material. stinging habits. Although there are no good data, ant stings are probably responsible for a number of Ants produce reproductive forms usually at one time human fatalities in the United States each year. The of the year (spring or fall, depending on species and effects of stings on a human depend on the ant colony disposition). Colony activity at the time of species and the sensitivity of the person. Most reproductive swarming is high, with winged males deaths are caused by a hypersensitive reaction and queens and workers in a very active state. The leading to anaphylactic shock. queen and males fly from the colony, mate, and shortly after, the male dies. The inseminated queen General Biology then builds a small nest, lays a few eggs, and nur­ tures the developing larvae that soon hatch from the Most ant colonies are started by a single inseminated eggs. When adult workers appear, they take over the female or queen. From this single individual, ant col­ function of caring for the queen, the larvae, building onies can grow to contain anywhere from several the nest, and bringing in food for the colony. Col­ hundred to several thousand individuals. Among the onies may persist for 20 years or more. largest ant colonies are the army ants of the American tropics, with up to several million workers, Since there are so many species of ants with ex­ and the driver ants of Africa, with up to 30-40 million tremely diverse habits, it is difficult to outline their workers. A thatching ant (Formica) colony in Japan general life style. Some ants are strictly carnivorous covering many acres was estimated to have about (army ants), while others may specialize by eating 348 million workers. However, most ant colonies pro­ fungi (the fungus ants), seeds (harvester ants), or the bably fall within the range of 300-50,000 individuals. "honeydew" of other insects. However, most ants that cause annoyance to homeowners are om­ Ants normally have three distinct castes: workers, nivorous and feed on a variety of foodstuffs which queens, and males. Males are intermediate in size include most of the food materials used by man. Various ants may make their nests in rotting logs, trees, soil, or even live inside the nests of other ants. ELBOWED ANTENNA PETIOLE Since they are such a diverse group, it is always best to check the habits of the particular species.

Identification

Ants are often confused with termites. Here is how to tell them apart:

ANTS

Strong constriction- petiole or "waist"-between thorax and abdomen (Fig. 1). Fig.1. Typical ant (illustrations not drawn to scale). Elbowed antennae (Fig. 1). Front pair of wings much larger than hind pair (Fig. 3a). BROADLY JOINED WAIST Various colors and hard-bodied.

TERMITES THORAX + ABDOMEN Abdomen broadly joined to thorax (Fig. 2). I \/ Straight antennae (Fig. 2). Both pairs of wings of about equal size (Fig. 3b). Usually whitish and soft-bodied.

Over the last 17 years, we have kept records of the troublesome ants of Washington. With a few minor exceptions, all pest species belong to one of the ten genera that follow. The key should allow you to ANTENNA distinguish these ten genera from each other. The key is only to worker ants. It will not work if males or queens are used. Fig.2. Typical Termite

KEY to workers (many of the characters will require use of a hand lens of 20X or greater).

Subfamily:

1. Abdominal petiole composed of one segment (Fig. 1)...... 2 Abdominal petiole composed of two segments (Fig. 4) ...... MYRMICINAE (Genera: Aphaenogaster, Monomorium, Pogonomyrmex, Solenopsis, Tetramorium).

Genera of Myrmicinae:

A. Epinotum without spines (Fig. 10) ...... B Epinotum with spines (Fig. 4b, 12) ...... C

B. Antennae with 10 segments, the last 2 forming a distinct club (Fig. 7, 13) ...... So/enopsis Antennae with 12 segments, no club as in Fig. 4, or club having 3 or or more segments (Figs. 6, 6a) ...... Monomorium

C. Psammophore (Fig. 4a) present ...... Pogonomyrmex Psammophore not present ...... D

D. Dorsal profile of thorax markedly step-like or sinuate (Fig. 12, 14A) ...... Aphaenogaster Dorsal profile of thorax even or only slightly indented (Fig. 14b) ...... Tetramorium

2 2. Cloacal orifice terminal, circular, surrounded by a fringe of hairs (Fig. 5a) ; petiolar node very prominent (Figs. 9-11) ...... (Genera: Lasius, Formica, Camponotus) Cloacal orifice ventral, transverse, slit-shaped , not surrounded by a fringe of hairs; petiolar node scale-like or vestigial (Figs. 5b, 8) ...... DOLICHODERINAE

(Genus Tapinoma) (since there is only one Dolichoderinae, no additional keys to these ants are required):

A. Thoracic dorsum, in profile (side view), evenly convex (Fig. 9) ...... Camponotus Thoracic dorsum, in profile, with a notch or dip (Fig. 10, 11 b) ...... B

B. Small ants (3-5 mm), usually light yellow to brown; clypeus short relative to its width (Fig. 30a) ...... Lasius Larger ants (7-9 mm or larger), usually bicolored, red and black (Fig. 10); clypeus, tall relative to its width (Fig. 30b) ...... Formica

In addition to the characters used in the key, you will find some characters listed under the individual genera or species which may be of use in your determinations.

HINDWING Fig . 3a. Ant wings.

F

Fig. 4b. SEM of epinotum armed with spines.

HI

Fig. 3b. Termite wings. SEGMENTED PETIOLE

SPINE~

Fig. Sa. Circular terminal orifice (at tip of Fig. 4a. Pogonomyrmex spp. (Harvester ants). * abdomen).

3 a

Fig. 7. Thief ant*, Solenopsis molesta. ORIFICE

PETIOLAR NODE

b

Fig. 5b. Transverse ventral orifice (a-lateral view; b-ventral view).

SEGMENTED PETIOLE

Fig. 8. Tapinoma sessile (Odorous house ant).*

Fig. 6. Pharaoh ant*, Monomorium pharaonis.

Fig. 8b. SEM closeup showing absence of petiolar node. THORACIC DORSUM

Fig. 6a. SEM of 3-segmented club of Monomorium sp. (SEM =Scanning Electron Micrograph) Fig. 9a. Camponotus spp. (Carpenter ants).*

4 Fig. 9b. SEM of Camponotus sp. thoracic dorsum.

.,.NOTCH Fig. 11 b. SEM closeup of thoracic profile.

Fig. 1Oa. Formica spp. (Western thatching and other ants).*

Fig. 12. Aphaenogaster spp. Lateral view of worker.*

Fig. 1Ob. SEM of thoracic dorsum depicting notch and absence of spines on epinotum.

Fig. 13. SEM of head and antenna of Solenopsis spp. * Fig. 11 a. Lasius spp. (Cornfield and other ants).* Note 2 segmented club on antenna.

5 THORAX STEP-LIKE Yellow ants and cornfield ants are collectively known as "moisture ants" in Washington. See EB1382, Moisture Ants.

Camponotus spp. (Carpenter Ants)

Recognized by evenly convex thoracic profile of workers. Color variable, with black or red and black bicolored species most common. Polymorphic species with workers ranging from 6-13mm long. THORAX EVEN Probably one of the most distinguishing features is that they are large ants. Colonies usually found in logs, trees, or some other wooden structure. Workers forage for dead or live insects, or common household foodstuffs for food. Reproductives pre­ sent in colony during winter and swarm during first warm days in spring (March-June, depending on locality). Several species distributed throughout the state of Washington. B Major concern: This group of ants can be considered Fig. 14. Ant profiles (a-step-like profile of thorax (see also as structural pests. While they will sometimes start Fig 12; b-more or less even thoracic profile). * their attack in wood in various stages of decay, they can and do attack sound wooden structures and can Principal Pest Ants of Washington be extremely damaging. They do not eat wood, but are merely clearing areas inside the wood in which Lasius spp. (Cornfield and Other Ants) to raise their brood. The moisture in the food , waste products, etc. also hastens decay of the wood. Most pest species yellow; can vary to a rather dark Remedial measures should obviously include the brown. Monomorphic species with workers all of location of the colony, the removal of all infested same size. Maxillary palpi long, 6 segmented. Col­ material and attendant rotten wood, and replace­ onies usually found in decayed logs and stumps, but ment with sound wood. It is important that the some may be found in soil. Also feed on sweet colony be located, as much undue alarm is caused materials, attend aphids for honeydew, and become by sexual forms that wander into homes during and a general annoyance factor around homes. after swarming but are not established in the house Reproductive swarming usually late summer to early or doing damage. (See EB0818, Carpenter Ants: autumn. Widely distributed genus, containing Their Biology and Control.) several species of pest status. Occur throughout state of Washington. Formica spp. (Western Thatching Ant and Other Ants) Major concern: These ants have frequently been found associated with rotting wood in houses. While Most species bicolored, red and black; some species several species may bring moisture into the wood can be uniformly brown or black. Large ants (7-9mm) structure to increase damage, the colony was initially with notch or depression in top of thorax, when started in wood in an advanced stage of decay. They viewed from side. Polymorphic with workers varying should not be considered a structural pest, as the in size. Usually nest in soil or in rotten logs. Many problem invariably existed before the colony was species make a thatch or mound of plant material, established. The obvious remedy is to remove the frequently grass. Rarely nest in homes, but can be decayed wood and to replace it with sound material. problem, as they feed on sweet materials and will also attend aphids for "honeydew." Reproductive swarms produced in late summer to early fall. One of most abundant ants; various species throughout Washington. *Figures 4. and 6.-12. and 14b., 21.-29. , and 14a. have been redrawn from USDA Tech. Bull. No. 1326, Bull. Mus. Camp. Zool. 204, and Ill. Nat. Hist. Surv. Bioi. Notes No. Major concern: They are usually only incidental 71, respectively. pests, but they can bite quite hard and usually spray

6 the area they have bitten with formic acid to produce elevated area where the workers deposit excavated a painful sensation. (See EB0929, Thatching Ants.) soil. All species feed on dead and live insects and other . Pogonomyrmex spp. (Harvester Ants) Major concern: Usually only an incidental pest for Most species reddish or reddish-brown . Monomor­ homeowners when the reproductives swarm in late phic with workers all same size (6-8mm). Easily summer to fall. Workers have a weak sting and will recognized by psammophore (Fig. 5) or beard under also bite if a nest is disturbed, but these are usually "chin," which is used as an aid in digging. Nest only considered minor annoyances by most people. The in sandy soil of a particular texture. Found only in sting can rarely penetrate human skin, bites also hurt eastern Washington and Columbia Basin. Ordinari­ only if inflicted in a sensitive, tender area (e.g., be­ ly feed on seeds of grasses and various weeds, but tween the fingers). can be problem in alkali bee beds. Reproductive swarming in spring. Monomorium spp. (Pharaoh Ant, Little Black Ant, .1 Others) l Major concern: This is one of the few ants in Washington that can give a person a rather severe The most important pest in this group is M. sting, somewhat like a bee or yellowjacket sting. pharaonis, the pharaoh ant, an introduced ant that Since the greatest number of colonies of these ants was originally native only to Africa. One of the most occurs along the Snake and Columbia River areas, common and best known of house-infesting ants. persons receiving stings are usually engaged in pic­ Workers monomorphic, ca. 2mm, yellow or light nicking, rock-hounding, or in some similar activity brown, with tip of body dark. Does not swarm, in the area. This is usually not a serious pest; few additional colonies are produced by the splitting of people are stung. large, mature colonies. All colonies have many queens. Tapinoma sessile (Odorous House Ant) Major concern: Omnivorous, will eat practically any Varies from brown to black. Monomorphic with all material in home, including bread, cookies, cakes, workers of approximately same size. Possesses anal sugar, syrup, liver, bacon, even dead insects. (See glands which produce a rotten, coconut-like odor. EB1514, Pharaoh Ant.) Workers range from 2.5-3.5mm long. Nests in wide variety of habitats from woodland, to beaches along Tetramorium caespitum (Pavement Ant) rivers and lakes, under bark of stumps and logs, and in houses. When alarmed, workers dash about with An introduced species. Monomorphic workers rang­ abdomens raised. Will tend aphids (plant lice) and ing from 2.5-3mm long. Body color ranges from light will also feed on wide variety of household foods, brown through brown to blackish, while the append­ such as raw and cooked meats, dairy products, and ages are lighter in color. Nest in exposed soil under vegetables; prefer sweets. Distributed throughout stones or pavement, in rotting wood, and in homes. Washington. Swarming occurs throughout the year but most com­ monly in June and July. Omnivorous. Feed on Major concern: It is primarily an annoyance factor seeds, honeydew, sap, dead and live insects, and because of its odor and preference for sweets that a variety of household foods. 1 are usually found in abundance in houses. (See EB1550, Odorous House Ant.) Major concern: Can be a nuisance house pest; also l a serious pest in alkali bee beds. Feed on seeds of Aphaenogaster spp. certain crops; will girdle or scarify certain plants such as tomatoes. Have been known to chew holes in gar­ Most species brown to reddish-brown, workers 4-6 ments. Can sting. There have been reports of skin mm long, monomorphic. Nests in wood in various reaction to these ants. Is an intermediate host of two stages of decay, or in cavities in sound wood, also species of poultry tapeworms. in soil beneath stones and logs. Colonies consist of up to 3,000 workers and several queens. Those col­ Solenopsis molesta (Thief ant) onies making their nest in soil are usually quite noticeable as the nest entrance is marked by an A native species and one of the smallest species of

7 ant occurring in Washington. Sometimes confused usually occurs from mid-summer to early fall. Highly with Pharaoh ants. Monomorphic workers ranging predaceous ants, however, will also feed on from 1.3-1.8mm long. Antenna! club unusually long. honeydew, nuts, grains, certain germinating crops, Body color ranges from yellowish or light brown to as well as many household foods. dark brown. Colonies consist of many hundreds to a few thousand individuals. Nest in exposed soil or Major concern: Can be a nuisance house pest. Feed under various objects. Also nest in rotting wood and on various crops. May be an intermediate host for in the woodwork and masonary of houses. Swarming one of the poultry tapeworm species.

Identification of Winged Reproductives The following key will help you identify common ants in many cases where only reproductive forms of ants Ideally, ant genera and species are identified using with wings are present. When workers are available, workers. Their more dependable characters lend you will find them easier to identify. themselves to identification when using a dichotomous key. Before you embark on the identification of winged ants, follow these pointers: Reproductive forms (queens and males) of ants pre­ sent a more difficult identification situation. Depen­ • You will need a 1OX hand lens or magnifying glass. dable characters are usually confined to differences • To prepare wings, carefully cut the forewing, in the wings, and a few other characters which are preferably with fine-pointed laboratory scissors, as not readily visible. Unfortunately, queens lose their close to the body as possible, and put into alcohol. wings shortly after mating, and so lose the best iden­ • Wing venation is much easier to observe if you tifying character. People often select a male or place the wing against a white background. queen ant for identification, and all too often, the • Be certain you have identified the specimen cor­ queen specimens are without wings. rectly as an ant.

Key to the Sexes (Winged Ants)

1. Head small in relation to body, tip of abdomen with clasping stuctures (Fig. 15.) ...... I. MALE

Head large in relation to body, tip of abdomen without clasping structures, sometimes

with a sting (Figs. 16, 17) ...... 0 •••••••••••• • ••••• 0 •••••• • ••••• 0 ••• • • •• II. QUEEN

One-segmented petiole ______showing prominent petiole node / I

Claspers

No sting, no claspers Fig. 15. Male carpenter ant. Fig. 160 Queen carpenter ant.

8 Two-segmented petiole ~orifice Sting

Fig. 17. Queen "Red Ant."* Fig. 18. Circular terminal orifice. ~A \ "f" /on 1ce ~8

Fig. 19. Transverse ventral orifice. Fig. 20. Tapinoma sessile (Queen odorous house ant). A. lateral view; B. ventral view.

I. Males

Males are nearly impossible to identify. The characters used are much too complex and are too small to see with anything other than the finest of microscopes. We suggest that you compare forewing venation with venations illustrated in the queen key for similarities. In many cases, wing venation of the male is identical to that of the corresponding queens. However, anomalies, such as one wing differing from the other, do occur, making male identification still more complicated.

Sometimes males will have the correct forewing venation pattern on one side and the pattern of another species on the other side. This occurs commonly on the wings of male Lasius spp.

II. Queens* (Key to Subfamilies and Genera)

1. Abdominal petiole one-segmented (Fig. 16) ...... 2 Abdominal petiole two-segmented (Fig 17) ...... Go to Key Ill Subfamily MYRMICINAE (Thief, pavement, wood, red, and pharoah ants).

2. Cloacal orifice circular, surrounded by fringe of hairs (Fig. 18), petiolar node prominent (Fig. 16), generally larger ants ranging from 4-17mm ...... Go to Key IV Subfamily FORMICINAE (Thatching, moisture, and carpenter ants).

Cloacal orifice slitlike (Fig. 19), petiolar node scalelike and barely noticeable (Fig. 20), generally about 4.5mm or less in length; forewings as in Fig. 21 ...... Subfamily DOLICHODERINAE (a single species known as the odorous house ant, Tapinoma sessile).

Ill Key to Myrmicinae (Queens)

1. Antennae with more than 10 segments, and without a terminal segmented club (as in Fig. 16) ..... 2

9 Antennae with 10 segments and with a distinct two-segmented club (Figs. 26a, 13), ants yellow to light or dark brown, about 6-7mm long, and wings as in Fig 26b ...... Thief ant (Solenopsis molesta)

2. Larger ants, 7-10mm long ...... 3

Small ants about 4.5mm long, yellow, and wings as in Fig 25, antennae with 12 segments ...... Pharaoh ant and allies (Monomorium spp.)

3. Very slender body, Bmm long, wings as in Fig. 22 ...... Pavement ant (Tetramorium caespitum)

Body more typical, as in Fig. 17, wings not as in Fig. 22 ...... 4

4. Wings as in Fig. 23; specimens range from 6-Bmm long ...... Red ants and allies (Myrmica spp.)

Wings as in Fig 24; body approximately Bmm long ...... Wood ants (Aphaenogaster spp.)

IV. Key to Formicinae (Queens)

1. Smaller ants ranging from 4-Bmm in length*; usually yellow or brown, wings as in Fig. 27; (clypeus short as in Fig. 30a) ...... Moisture ants (Lasius spp.)

Larger ants, usually 8mm or more in length (although some Formica queens are slightly smaller) (If this is the case, check clypeus; clypeus taller, as in Fig. 30b), frequently red and black, black or dark brown ...... 2

2. Large ants ranging from 13-17mm in length; wing venation as in Fig. 28 ...... Carpenter ants (Camponotus spp.)

Medium size ants ranging from 6-10.5mm in length, wing venation as in Fig. 29 ...... Thatching ants (Formica spp.)

Fig . 21. Forewing of Tapinoma sessile. * Fig. 22. Tetramorium caespitum forewing.*

Fig. 23. Myrmica sp. forewing.* Fig. 24. Aphaenogaster sp. forewing.*

Fig. 25. Monomorium sp. forewing. * Fig. 26. Solenopsis sp. A. Head and antennae of Queen, B. Forewing. *

10 Fig. 27. Lasius sp. forewing.* Fig. 28. Camponotus sp. forewing.*

ClYPEUS

Fig. 29. Formica sp. forewing.* Fig. 30. Comparison of depths of lengths of the clypeus of Lasius sp. (a) with that of Formica sp. (b) queen. (Redrawn from Ill. Nat. Hist. Survey Bioi. Notes. No. 71)

Fig. 31. Reference guide for millimeters and inches.

*There are some relatively rare occurrences of Camponotus hyatti, and they fit within this size range as queens. Check wing venation closely. References

Akre, R.D., L.D. Hansen, and A.L. Antonelli. Creighton, W.S. The Ants of North America. Bull. EB0818, Carpenter Ants: Their Biology and Control. Mus. Camp. Zool. Harvard; Cambridge, MA, 1950, CES-WSU, 1991, 6 pages. Vol. 104, 57 Plates.

Akre, R.D. and A.L. Antonelli. EB0929, Thatching Ross, H.H., G.L. Rotramel, and W.E. LaBerge. A Ants. CES-WSU, 1992, 2 pages. Synopsis of Common and Economic Illinois Ants, with Keys to the Genera (Hymenoptera, Formicidae). Akre, R.D., and A.L. Antonelli. EB1382, Moisture Illinois Nat. Hist. Surv. Bioi. Notes No. 71, 1971. Ants. CES-WSU, 1991, 4 pages. Smith, M.R. House Infesting Ants of the Eastern Akre, R.D. and A.L. Antonelli. EB1550, Odorous United States. USDA Tech. Bull. 1326, 1965. House Ant. CES-WSU, 1989, 2 pages.

Antonelli, A.L. and R.D. Akre. EB1514, Pharaoh Ant. CES-WSU, 1989, 3 pages.

Photo credits-SEM shots by Dr. Greg Paulson.

11

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