The Hymenoptera & Sociality Topic 13

Exopterygota Endopterygota Entognatha Insecta Apterygota Pterygota (Microcoryphia) (Thysanura) Apterygota Pterygota Palaeoptera Neoptera Exopterygota (Neoptera) Endopterygota (Neoptera)

The Hymenoptera Ants, wasps, bees, and others “hymeno” = membrane/married; “ptera” = wing Third largest order after the Coleoptera + Diptera >150,000 sp. WW >18,000 sp. NA Most mandibulate; some haustellate Two pairs of linked wings 3 ocelli present; compound eyes Often with complex social system

Hamuli “hamus” (Latin) = hook; “hamulus” = diminutive form (little hook)

Schmidt Pain Index In the 1980’s Justin Schmidt wanted to test the painfulness and duration of stings of different Hymenoptera. He tested 78 species. Index: measured on a 5-point scale, 0-4 0 = insect cannot penetrate skin 4 = most painful

Venom LD50s LD50 = Family Species Common Name LD50 (mg/kg) Reference Apidae Apis mellifera honey bee 2.8 Schmidt 1990 Mutillidae Dasymutilla klugii velvet ant 71 Schmidt et al. 1980 Vespidae Polistes canadensis paper wasp 2.4 Vespula squamosa yellowjacket 3.5 Formicidae Pogonomyrmex spp. harvester ants 0.66 P. maricopa harvester ant 0.12 Schmidt et al. 1989

1. 0 Sweat bee: Light, ephemeral, almost fruity 1.0 Sweat bee: Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm. 1.2 Fire ant: Sharp, sudden, mildly alarming. Like walking across a shag carpet & reaching for the light switch. 1.8 Bullhorn acacia ant: A rare, piercing, elevated sort of pain. Someone has fired a staple into your cheek. 2.0 Bald-faced hornet: Rich, hearty, slightly crunchy. Similar to getting your hand mashed in a revolving door. 2.0 Yellowjacket: Hot and smoky, almost irreverent. Imagine W. C. Fields extinguishing a cigar on your tongue. 2.x Honey bee and European hornet: Like a matchhead that flips off and burns on your skin. 3.0 Red harvester ant: Bold and unrelenting. Somebody is using a drill to excavate your ingrown toenail. 3.0 Paper wasp: Caustic & burning. Distinctly bitter aftertaste. Like spilling a beaker of hydrochloric acid on a paper cut. 4.0 Pepsis wasp: Blinding, fierce, shockingly electric. A running hair drier has been dropped into your bubble bath. 4.0+ Bullet ant: Pure, intense, brilliant pain. Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel.

Chris Starr pain index Rating Insects 1.0 Southern fire ant (Solenopsis xyloni) 2.0 Honeybee, Africanized bee, bumble-bee, yellow-jacket ("common wasp") 3.0 Velvet ant, paper wasp 4.0 Tarantula hawk (Pepsis wasp) 4+ Bullet ant (Paraponera clavata) 0 – no pain; 1 – pain so slight as to constitute no real deterrent; 2 – painful; 3 – sharply and seriously painful; 4 – traumatically painful

Who da man? The “hormiga veinticuatro”

Hormiga veintriquatro

Evolution of Hymenoptera Phytophagy is ancestral

Two major subgroups (used to be suborders) “Symphyta” = sawflies, horntails, wood wasps Have broad or unconstricted waist between thorax and abdomen Eruciform larvae with prolegs, stemmata Apocrita = wasps, bees, ants Have obvious constriction between thorax and abdomen (called petiolate) First abdominal segment is fused to thorax Larvae legless, without prolegs, without ocelli

“Symphyta” is paraphyletic

The sawflies

Horntails

Sirex spp., the horntails

The Apocrita – bees, wasps, ants The Apocrita have a greater degree of constriction between thorax and abdomen

The two types of Apocrita Aculeates = the stinging Apocrita Bees, many wasps, ants Ovipositor modified as a sting “Parasitica” = the parasitic Apocrita Many wasps, including Ichneumonidae

Apocritan immatures - honeybee

Families usually collected Symphyta – Tenthredinidae or other Apidae Bumblebees Carpenter bees Other Halictidae (sweat bees) Andrenidae (mason or mining bees) Pompillidae (spider wasps/hakws) Sphecidae (digger wasps) Vespidae (yellow jackets, bald-faced hornets, etc.) Mutillidae (velvet ants) Formicidae (ants) Ichneumonidae (ichneumon wasps) Braconidae

Branched hairs in the bees

Wasps vs. bees Wasps generally lack corbiculae, have unbranched setae over their body surface, and have a much more constricted thorax-abdomen division

Mouthparts Bees tend to be haustellate (suck up fluids), while wasps are more mandibulate

To bee or not to be… Most bees have a corbicula or “pollen basket” to gather pollen

Apidae - bumbles, carpenters, honeys

Apidae vs. Andrenidae

Halictidae – sweat bees Halictids are often metallic and are attracted to perspiration

Vespidae & Sphecidae Vespids and sphecids are common wasps; sphecids usually have a thin waist, but not always

Sphecidae – digger wasps/mud daubers Sphecids have an obvious rounded lobe on the pronotum

Pompilidae – spider wasps Spider wasps often have curly antennae and are iridescent; also have a transverse/slanted suture on the thorax

Spider wasp

Ichneumonidae

Mutillidae – velvet ants

Mimicry rings

Formicidae - ants Ants are named for the secretion of formic acid, used for defense

Working collectively…

Polymorphism in ants

Ant “alates”

Eusociality

Eusociality Cooperative brood care, even of those unrelated Overlapping generations within a colony Division of labor (different castes) Reproductives Non-reproductives/workers (sterile caste)

Determination of caste

Sex determination in Hymenoptera Females are diploid (2N) and develop from fertilized eggs Males are haploid (1N) and develop from unfertilized eggs

Haplodiploidy to explain evolution of eusociality Female offspring of a male will have 100% of his genes, but only 50% of their mother’s Sisters thus share 75% of their genes with each other Why does this matter if the sisters cannot reproduce? (only the queen or reproductives can reproduce) If sisters are helping each other in a colonial, eusocial system, they are ensuring that their collective genes are being passed on **note that many hymenopterans are eusocial but not haplodiploid

What about termites? Termites are also eusocial, but do not have haplodiploidy! Sisters thus share only ~50% of their genes in common and 50% with either parent, so why are termites eusocial?

Hymies vs. Isoptera Hymenoptera Isoptera 0, 1, or >1 queen No kings No real “soldier” caste Queen can mate only once, or many times with multiple males Haplodiploid system Only 1 queen 1 king Soldier caste Queen mates monogamously with one king No haplodiploid system Males are diploid