Species Vespula squamosa - Southern Yellowjacket

Vespula squamosa (Drury 1773)

Forewing: worker 9.5–11.0 mm, ♀ 15.0–16.5 mm, ♂ ~12.5 mm

Distinctive; all castes possess conspicuous yellow longitudinal stripes on the mesoscutum, a trait shared with the closely-related allopatric V. sulphurea but no species within its range. The queens and workers are dimorphic. Workers and males have similar abdominal patterns, with no free spots and an unusual pair of lateral yellow stripes through the black basal band of the second tergite. Queens are quite large for a yellowjacket, with orange fascia on the abdomen expanded to nearly obliterate the dark markings.(1)(2)

   

e. US to Honduras. The most southerly Vespula species(3)(4); Recorded in e. and w. CT on iNaturalist (2023), which is the easternmost record.

A colony found in southwestern Pennsylvania was subterranean in a large open grassy field (B. Coulter, pers. ob.). This species has a propensity to build (or usurp) nests in disturbed habitats.(1)

Emerges in spring later than its frequent host, Vespula maculifrons, so that there are numerous young colonies available for usurpation. In the southeastern US, it typically appears about a month after maculifrons, and the colonies tend to decline in November in most of the range (earlier than maculifrons).(1) This species is the most frequent native Vespula to form perennial polygynous colonies in the southernmost portions of its range.

Queens are facultative temporary social parasites, and frequently usurp established young nests of other yellowjacket species, usually V. maculifrons. There are also records of this species utilizing V. vidua and V. flavopilosa(5) as hosts. The queens are extremely large and robust for a yellowjacket, a trait which surely helps them to overpower and kill the host queens of the colonies they usurp. A study in Georgia found that about 80% of V. squamosa colonies began by usurpation of a V. maculifrons colony.(1) Facultative temporary social parasitism means that the species may parasitize other species, but is still capable of founding its own colonies, and it retains a worker caste. After killing the host queen, the squamosa adopts the nest and host workers, who raise her offspring. The colony eventually becomes pure squamosa as the original host workers die off.

Several mimics exist:

Spilomyia texana (Diptera: Syrphidae)

Milesia scutellata (Diptera: Syrphidae)

Milesia scutellata (Diptera: Syrphidae)

Paranthrene simulans (Lepidoptera: Sesiidae)

Tissot A.N., Robinson F.A. (1954) Some unusual insect nests. Fla. Entomol. 37: 73-92. Full text