Key to genera and supra-generic groups of Sphecidae based on morphology of last instar larvae, cocoon and behavior

Some strongly stereotyped behavioural features of adults (nest construction and provisioning) and larvae (cocoon construction) were additionally used in the key because they are remarkably useful in distinguishing immature instars belonging to genera and supra-generic groups of Sphecidae and because collectors usually find sphecid larvae concealed in their nests, wherein biological features can be observed. The colour of the larvae must be observed on fresh specimens. The following genera are not included in the key because their larvae are unknown: Chilosphex Menke in R. Bohart & Menke, Dynatus Lepeletier, Eremnophila Menke, Eremochares Gribodo, Hoplamophila de Beaumont, Parapsamophila Taschenberg, Stangeela Menke, Trigonopsis Perty.

1a. Prothorax with two or three pairs of callosities; labrum with sensorial cones on the margin; epipharynx without a pigmented marginal band bearing sensillae; cocoon formed by one silken capsule........................................... 2

1b. Prothorax without callosities; labrum without sensorial cones on the margin; epipharynx with a pigmented marginal band bearing basiconic sensillae; cocoon formed by two or three concentric silken capsules.................................. 5

2a. Prothorax callosities little developed; cephalic rugosity absent; thoracic spiracles smaller than the abdominal ones; larvae found in ground nests, provisioned with Gryllidae and cockroaches—Chloriontinae............................................................................................. Chlorion (Cosmopolitan, absent in Europe and Australia)

2b. Prothorax callosities well developed; cephalic rugosity present, all spiracles about the same diameter...... Sceliphrinae … 3

3a. Body distinctly yellow; prothorax with one or two pairs of little sclerotized and unpigmented callosities (possibly a second pair of callosities is always present, but sometimes it is barely visible); larvae found usually in mud nests, provisioned with spiders Sceliphrini .......................... Sceliphron (Cosmopolitan) or Chalybion (Cosmopolitan, absent in South America)

3b. Body white, sometimes greyish or yellowish; prothorax with three pairs of sclerotized and brownish callosities; larvae found in ground nests or nests constructed in pre-existent cavities in wood, provisioned with cockroaches............. Podiini … 4

4a. Posterior extremity of cocoon with a mamilliform projection bearing an apical opening through which the faeces are expelled............................................................................... Penepodium (Neotropical)

4b. Cocoon without a mamilliform projection or openings............ Podium (Neotropical, two species reach North America)

5a. Mandible without denticles on external surface; nests provisioned with ortopteroids insects................ Sphecinae … 6

5b. Mandible with denticles on external surface; nests provisioned with caterpillars..................... Ammophilinae … 9

6a. Thorax and segment AI abruptly tapering; cocoon fusiform in shape................................ Prionychina … 7

6b. Thorax and segment AI similar to other abdominal segment; cocoon approximately cylindrical with extremities rounded... 8

7a. Head longer than wide; larvae found in ground nests, provisioned with Acrididae ................. Prionyx (Cosmopolitan)

7b. Head broader than long; larvae found in nests constructed in pre-existent cavities and usually provisioned with Tettigoniidae .................................................................................... Palmodes (Holarctic)

8a. Mesothorax with pair of dorsal elevations; atrium wall ornamented with polygons; larvae found in nests constructed in preexistent cavities, usually lined inside with leaves or other plant debris........................ Isodontia (Cosmopolitan)

8b. Mesothorax without dorsal elevations; atrium wall ornamented with concentric annulets; larvae found in nests excavated in the ground, never lined inside with leaves or other plant debris................................... Sphex (Cosmopolitan)

9a. Mandible with four teeth (the fourth one can be reduced or divided in small denticles), internal margin without denticles.................................................................................. Ammophila (Cosmopolitan)

9b. Mandible with three teeth and several small denticles in the internal margin, basad to the third tooth............................................................................... Podalonia (Cosmopolitan, absent in South America)