488 
The Ohio Naturalist. 
[Vol. XII, No. 5, 
are usually black, with a yellow tip; sometimes there is a trace of 
yellow at the base; hind tibiae usually with a brown ring in the 
middle. 
The adults have been taken in large numbers about blossoming 
willow (. Salix sp.) as early as the last few days of March and the 
first of April, and again about blossoming apple and pear, the 
first of May. They are abundant in mid-summer and can be 
taken about all kinds of blossoms. 
They are pollen and nectar feeders and doubtless of consider- 
able importance as pollenizers of fruit trees and other plants. 
For this, and their work in checking aphids, they are worthy every 
protection that can possibly be afforded them. 
EXPLANATION OF PLATE XXIII. 
Fig. 41. Egg from the side x 17. 
Fig. 42. Dorsal view of egg x 17. 
Fig. 43. A small part of the surface of egg-shell showing sculpturing, 
highly magnified. 
Fig. 44. Adult about 5 times natural size. 
Fig. 45. Larva just hatched x 50; a, posterior respiratory appendage. 
Fig. 46. Full-grown larva x 7; a, antenna, b, anterior spiracle, c, 
posterior respiratory appendage. 
Fig. 47. Anterior view of larva, much enlarged, showing mouth-parts, 
antennae, etc.; a, right anterior spiracle; b, antenna; c, upper 
jaw; d, lower jaw; e, the three pairs of mouth-hooks. 
Fig. 48. Dorsal view of right anterior spiracle, highly magnified. 
Fig. 49. End or posterior view of posterior respiratory organ x 55; a, 
dorsal spiracular spine; b , one of the three pairs of slit-like 
spiracles. 
Fig. 50. Side or dorsal view of posterior respiratory organ x 55; lettering 
as in Fig. 49. 
Fig. 51. Appearance of a part of the puparium externally in the region of 
the mouth-parts much enlarged; a, right anterior spiracle with 
short piece of trachea attached; b, lower jaw of larva; c, upper 
jaw of larva; d, chitinous oesophageal framework; e, mouth- 
hooks of larva. 
Fig. 52. Hind leg of pupa showing flexure of tibia at a. 
Fig. 53. An early pupal stage from the side; a, b, and c, developing legs; 
d, w r ing-pad; e, mouth-parts. 
Fig. 54. A much later pupal stage, ventral view; a, the delicate investing 
membrane. 
Fig. 55. Dorsal view of puparium x 5; a , posterior respiratory organ. 
Fig. 56. Outline of puparium from the side. The dotted outline is given 
to show the typical shape of a parasitized puparium. 
Fig. 57. Lateral view of head of female x 7. 
Fig. 58. Larva of parasite, Bassus laetatorius, mouth-parts at a, ventral view. 
Fig. 59. Pupa of B. laetatorius, ventral view. 
Figs. 53, 54, 58, and 59 each about 5 times natural size. 
