Published August 20, 1990:

• Holorusia hespera, a new name for Holorusia grandis (Bergroth) (=Holorusia rubiginosa Loew) (Diptera: Tipulidae), by P. H. Arnaud, Jr. & G. S. Byers, p. 1-9.
• Parasitism of Anuroctonus phaiodactylus (Wood) and Vaejovis spinigerus (Wood) (Scorpiones: Vaejovidae) by Spilochaetosoma californicum Smith (Diptera: Tachinidae), and a review of parasitism in scorpions, by S. C. Williams, P. H. Arnaud, Jr. & G. Lowe, p. 11-27.
• Historical account and illustrations of the specimen identified as the male of Lespesia ciliata (Macquart) by Robineau-Desvoidy in 1863 (Diptera: Tachinidae), by P. H. Arnaud, Jr., p. 29-40.

Published July 29, 1994:

• The adult Thaumaleidae (Diptera: Culicomorpha) of western America, by P. H. Arnaud, Jr. & I. A. Boussy, p. 41-152.
• The taxonomy and biology of the immature stages of species of Thaumalea occuring in Idaho and California (Diptera: Thaumaleidae), by J. M. Gillespie, W. F. Barr & S. T. Elliott, p. 153-193.
• External structure of larval Thaumalea buckae Arnaud and Boussy (Diptera: Thaumaleidae), by I. A. Boussy, J. M. Gillespie & P. H. Arnaud, Jr., p. 195-201.
• Tipula efembrowni a new name for Tipula decorata Brown, 1985 (Diptera: Tipulidae), by P. H. Arnaud, Jr., p. 203-205.
• Tachina garretti, a new name for the Nearctic Tachina pilosa (Tothill, 1924) (Diptera: Tachinidae), by P. H. Arnaud, Jr., p. 207-208.
• The Rudolf Hans Bock Lepidoptera Collection donated to the California Academy of Sciences, by P. H. Arnaud, Jr., p. 209-210.
• Obituary: James Wilson Tilden (1904-1988), by P. H. Arnaud, Jr., p. 211-224.
• Obituary: Thomas William Davies (1915-1990), by P. H. Arnaud, Jr., p. 225-238.
• Manuscript reviewers, p. 239.
• Index to new names proposed in MYIA 5, p. 240.