A Study of the Bacteria Associated with Thirty Species of Insects

Abstract

83 strains of bacteria, 2 strains of yeasts, and 2 molds, isolated from 30 spp. of insects, were studied in detail with respect to their morph. and physiol. characteristics. The insects examined included spp. from 7 orders of the Hexopoda. Of the 83 strains of bacteria isolated, 44 (53%) were gram-negative short rods, 17 (20.5%) were gram-positive cocci, 10 (12%) were gram-positive short rods and 12 (14.5%) were gram-positive spore-formers. According to genera, there were 7 strains of Escherichia, 10 of Aerobacter, 2 of Aerobacter or Klebsiella, 3 of Proteus, 4 of Eberthella, 1 of Serratia, 3 of Pseudomonas, 3 of Alcaligenes, 2 of Achromobacter, 8 of Flavobacterium, 9 of Bacterium, 8 ofMicrococcus, 1 of Sarcina, 5 of Streptococcus, 12 of Bacillus, 2 of Corynebacterium, and 3 strains of unidentified bacteria, 2 strains of unidentified yeasts, and 2 molds each of the genera Mucor and Aspergillus. No gram-negative cocci or true spirilla were cultured. Of the 83 strains of bacteria, 29 did not conform to descriptions given in Bergey''s Manual and are probably new strains. Of the 29 new strains, 23 were different, there being several duplicates. The 23 organisms are described in detail and of these 18 were the following new specific names: Proteus insecticolens and P. recticolens from the milkweed bug, Oncopeltus jasciatus, Texas; Eberthella insecticola from O. f. and the grasshopper, Conocephalus jasciatus, and probably from the stink bug Loxa variegata, Flavobacterius chlorum from the lady beetle, Coccinella novemnotata, F. acidificum from Conocephalus jasciatus, Leptinotarsa decemlineata, a lady beetle larva and Pierus rapae, Bacterium hebetisiccus from walking stick, Diapheromera femorata, B. intrinsectum from unidentified Chrysomelid leaf beetle; B. qualis, (probably) Lygus pratensis, B. tegumenticola from bedbug, Cimex lectularius, B. mutabile from lyreman cicada, Tibicen linnei, B. incertum from Tibicen linnei, B. imperiale from the imperial moth, Eacles imperialis, B. insectiphilium from the bagworm, Thyridopteryx ephemeraejormis, B. minutiferula from the mud-dauber wasp, Sceliphron cementarium, Micrococcus nonfermentans from Tibicen linnei and an unidentified damsel fly (Coenagrionidae); Bacillus aerifaciens from Pieris rapae, B. immobilis from the larvae of Ceratomia catalpae; and Corynebacterium paurometabolum from Cimex lectularius. The majority of the insects examined were plant-feeders. With the exception of a species of aphid, an occasional sphinx moth caterpillar (Ceratomia catalpae), and bedbug (Cimex lectularius), bacteria were found in the alimentary tract of every insect specimen examined. In most cases the species of bacteria found in the several specimens of any given species of insect were surprisingly constant. Furthermore, there were at least 10 instances of duplication of specific strains, of bacteria as they occurred in the different insect species.