Text and pictures by Don McIntire
When we think of the Hymenoptera – Ants, Bees, Wasps and Sawflies, we think of the great role they play in the pollination of plants. But that’s not the whole story – Hymenoptera have reached a pinnacle in their behavioral response to the pressures of defense, feeding, nesting and reproduction. They are the “smart insects.” Honey Bees, with their language, Sphecid Wasps with their specialization of prey and nesting habits, and the indomitable Ant society, which does it all. Ants have communication systems, harvest, farm, raid, raise livestock, keep pets, protect plants and build elaborate cities. Kind of like the peopleants. At Torrey Pines, the ants are the primary food for the horned lizard, western skink and red-shafted flicker.
To find where and how exactly the Hymenopteran fits into the ecosystem is to sit on the beach and count grains of sand. Each has their specialty of habitats, hosts, ranges and food. The larger groups of Hymenopterans are rarely seen. They are the families of the Micro-hymenoptera which are mainly the parasitoids of the superfamily Chalcidoidea. The Myrmaridae, or fairyflies, which are primarily egg parasites, are so small, 0.21 mm, that they can fly through the eye of a needle – and they are common to Torrey Pines Reserve and most parts of the world.
Here are some more examples of insects in the Reserve.
Yellow and Black Mud Dauber (Sceliphron caementarium)
Adult: 25 mm
Order Hymenoptera/ Family Sphecidae – Thread-waisted Wasps
This familiar species is commonly seen around wet areas where the females gather mud with their mandibles, taking it to some secluded or protected spot to build their mud nests. This can be under the eaves of houses, bridges, wood piles or even in the wheel wells of old abandoned cars. How many trips to build each single cell cannot be calculated, but a single concentric layer at approximately 1/16” wide and ¾” long may take several. You can often see the layers as rings in the mud going end to end. The cells are provisioned with various spiders which are paralyzed and a single egg is lain within each cell, then sealed. In the picture, you can see what is left of the pupae which never matured. This was probably due to attack by parasitic wasps or flies. These parasites usually lay their eggs in the open cell while the wasp is away to get more provisions. Another wasp which is often seen visiting the old nests of the Yellow and Black Mud Dauber is Chalybion californicum, the Blue Mud Dauber, a beautiful steel blue species, which cleans out and patches up the old abandoned cells for her own brood.
Velvet Ants – What appear to be small wingless bumblebees having reddish to whitish hair are sometimes seen wandering about on the trails. While called velvet ants (see also Sacken’s Velvet Ant below) because of their appearance, they are actually female wasps in one wasp family. The males, which have wings, are seldom seen. Don’t handle these insects, for they can give a painful sting.
Sacken’s Velvet Ant (Dasymutilla sackeni)
Adult: Female 18 mm
Male 10 mm
Order Hymenoptera/ Family Mutillidae – Velvet Ants
Females are wingless, the males winged. This species is most common on the dune areas at the Reserve. Clad with long hairs, like dune insects in general, this creates an air space around the insect should the sand cave in upon it. This helps the insect to better free itself and also protects the body from the abrasion of the sand. Sacken’s Velvet Ant is parasitic on a number of types of bees and wasps, but is often seen to enter the burrows of sand wasps, Bembix spp.. The integument of Mutillid wasps is so hard that it is very difficult to pierce them with a steel insect pin. With such armor they are well protected from the stinging insects which they attack, and are also provided with a severe stinging ability for any potential predators. Range for this and the following species is throughout most areas of the state at lower elevations where there is suitable habitat.
Red-haired Velvet Ant (Dasymutilla coccineohirta)
Adult: Female 11 mm; Male 7-8 mm
The Red-haired Velvet Ant is most commonly seen along dusty or sandy paths at the Reserve. Host preferences are little known. Do not pick up Mutillids, the sting is memorable!
Valley Carpenter Bee (Xylocopa varipuncta)
Adult: Female 30 mm; Male 22 mm
Order Hymenoptera/ Family Anthophoridae/ Subfamily Xylocopinae – Carpenter bees
These are the largest bees in California and common throughout San Diego County at lower elevations from coast to foothills. Like many different kinds of animals often do, the males and females exhibit sexual dimorphism, the females black, the males blonde.
The remarkable males, rarely noticed, are extremely active in the early spring when they set the stage for their trysts with the females, each guarding a particular area near the dead trees or telephone poles from which they were born. They circle their area at dizzying speeds and often stop to hover and watch for intruders of their own kind, which they will chase away, but never seem to land and rest.
The black females were seen hovering and landing at the top of an old telephone pole used by a Kestrel as a perch in the natural area between Carmel Valley Road and the railroad tracks, indicating a nesting site. The bees often use such old weathered poles, timbers and dead trees as the wood begins to disintegrate. A full description of their nesting habits can be found in California Insects by Powell and Hogue. Watch for these bees visiting any large yellow flowers in your neighborhood. The introduced Cassia didymobotrya will always attract them if they are in your area.
Tarantula Hawk (Pepsis mildei)
Adult: Wingspan; 84 mm; Body; 40 mm
Order Hymenoptera/ Family Pompilidae – Spider wasps
This large wasp hunts spiders of the genus Eurypelma, tarantulas, which are fairly common to the upland areas of the reserve. The spiders are usually hidden either in burrows or under stones during the day but become active at dusk to early morning. They are not as large as the tarantulas often seen crossing roads in the desert, but have a legspan to about 10cm. or more. The female wasps may dig a burrow a foot or more below ground to deposit the immobilized spider and lay a single egg on it, returning to the surface to seal it. The adult Pepsis spp. feed on nectar and pollen of mostly Asteraceae at the reserve, but are also fond of the introduced sweet fennel Foeniculum vulgare. This species is most active from June to November.
Western Cicada Killer (Sphecius convalis)
Adult: Body 30 mm; Wingspan 45 mm
Order Hymenoptera/ Family Sphecidae – Thread-waisted wasps
The western cicada killer ranges throughout the county in a variety of habitats. The female is able to carry a large cicada in flight. She digs a single-celled chamber in soft earth, deposits the paralyzed cicada and lays a single egg on it. The female specimen pictured was found at Los Peñasquitos Lagoon area.
Next topic: Moths