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 Latest Fontana Road Trip (PAGE 3): March 24 - 27 2025 
  Fontana Road Trip Page 1    Fontana Road Trip Page 2  
Cameras: Nikon D-90 (ant macros), Sony HX-60 & iPhone 12
W.P. Armstrong 28 March 2025
A short road trip to survey ants in undeveloped land under high voltage transmission lines on north side of Baseline Ave., Fontana, CA. Urbanization, including landscaped housing tracts has resulted in the displacement of native, seed-harvesting ant colonies, including Veromessor, Pogonomyrmex & Pheidole. On this trip I discoverd nests of pyramid ants (Dorymyrmex bicolor) and orange desert ants (Forelius pruinosus).

In this urbanized area of Fontana, CA there were once vast grape vineyards covering thousands of acres. There is still open land under high voltage transmission lines passing through housing developments. A number of interesting seed-harvesting ant species still build their nests in this area.

Dolichoderinae: Forelius pruinosus

What I thought was a Pheidole nest turned out to be Forelius pruinosus, minute ants that are common in San Diego County. They have been called "high noon ants" because in desert areas they are active in the hottest part of the day when other ant species retreat into their nests. This ant continues foraging even during the hottest days when the dark, metavolcanic rock on Owens Peak near Palomar College is almost too hot to touch. Although I have photographed them on Owens Peak, I didn't recognize them under Fontana power lines. In fact, using Dr. Phil Ward's "Key To Ant Genera Of California" I misidentified them as 'little yellow ants" (Plagiolepis alluaudi). My mistake was where the key refers to the shape of metasomal orifice (anus in layman terms). I chose "circular" orifice when the correct choice was "slit-shaped orifice." See following image for more detailed explanation of my error.

Microscopic view of the rear-end of Forelius pruinosis. There is a faint "slit-shaped orifice" (black arrow). This takes you to the genus Forelius in the subfamily Dolichoderinae. The sister choice "circular orifice" takes you to the genus Plagiolepis in the subfamily Formicinae.

  See Forelius pruinosus on Owens Peak Near Palomar College, San Diego County  

I probably should mention one more factor in my failure to recognize Forelius pruinosus: Memory Lapse! I have observed and photographed this species many times in my ant-hunting trips in California, Arizona and New Mexico. On this current trip I completely forgot about Forelius. Consequently, I used Phil Ward's "Key To Genera Of California Ants" and took a wrong turn in the key where the shape of metasomal orifice is critical. I ended up at the genus Plagiolepis, the "little yellow ant" (Plagiolepis alluaudi). I was very excited about the possibility of finding a new ant for California. This is especially true since I photographed this ant on the island of Maui. See following image. The little yellow ant (F), Plagiolepis alluaudi, is at bottom.

Six Hawaiian Ant Species On Maui

There are no native ants on the Hawaiian Islands, but there are more than 50 introduced species. Some of these are an ecological disaster, and pose a serious threat to indigenous species. In fact, the Argentine ant locally threatens insects that pollinate the endemic silver sword on Haleakala.

A. The large ant at top is a Hawaiian carpenter ant (Camponotus variegatus). Its body is 14 mm long (just over 1/2 inch); B. White-Footed Ant (Technomyrmex albipes); C. Rover ant (Brachymyrmex obscurior); D. Big-headed ant minor worker (Pheidole megacephala); E. The long-legged ant with long scape (lower right) may be the yellow crazy ant (Anoplolepis gracilipes), not to be confused with the long-horned crazy ant (Paratrechina longicornis); F. The little yellow ant at bottom (Plagiolepis alluaudi) is one of the world's smallest ants with a body only 1/20th of an inch in length (slightly over one millimeter). Image taken with a Nikon D-90.

  See Little Yellow Ant Plagiolepis aluaudi from the Island of Maui  

Dolichoderinae: Forelius pruinosus In New Mexico
Another Confusing Forelius Encounter In Albuquerque

My March 2025 Fontana trip was not the first time I was confused with the identity of Forelius even though I had seen and photographed it many times before.

Small Red & Black Ants At Crown Plaza Hotel, Albuquerque, NM (July 2016).

There were trails of small ants on sidewalk of Crown Plaza Hotel in downtown Albuquerque, NM. They appeared to be in the Dolichoderinae and superficially resembled Forelius in terms of their size (overall length about 2 -2.5 mm), ant trails and speed, except their gasters were black. They appeared too small for Dorymyrmex bicolor and most of them did not have a definitive cone (spine) on pronotum. They had 12-segmented antennae, although segments were very minute and difficult to count. I did not see an acidopore at tip of gaster. In addition, they had a single petiole node and no propodeal spines.

According to Phil Ward, UC Davis (Personal Communication, 26 Jan. 2017), this was the highly variable Forelius pruinosus. "Forelius pruinosus: Albuquerque, NM; light with darker gaster; these specimens fall under the rubric of western "pruinosus", which is highly variable in color and pilosity."

  Forelius pruinosus in Albuquerque, New Mexico  

Dolichoderinae: Dorymyrmex bicolor
Distinctive nest of pyramid ant (Dorymyrmex bicolor) another small ant in the subfamily Dolichoderinae. This species is sometimes called "pyramid ant" because of the circular, crater-like mound surrounding the entrance to its nest. It is a small, soil-dwelling ant just over 3 mm in length. Unlike the polymorphic southern fire ant (Solenopsis xyloni), it does not sting. Although it tolerates hot arid places along dirt roads and grassy areas, it retreats into its subterranean burrow during the intense heat of a summer day. The most notable characteristic of Dorymyrmex is a prominent, dorsal, cone-like protuberance on its propodeum. Although it is at the posterior end of thorax, this is technically the 1st segment of the abdomen

  See Dorymyrmex bicolor on Owens Peak Near Palomar College, San Diego County