102 THE UNIVERSITY SCIENCE BULLETIN. 
the aquarium was seen to crawl up the side of the jar bearing an adult 
female Mesovelia with its beak attached near the caudal end of the 
fly, which when disturbed flew to a nearby support, bearing the tenacious 
little bug. 
However, the writer has come to believe that, with Hydrometra, 
Microvelia and Rheumatobates, they are not dependent upon the chance 
and uncertain fare of terrestrial insects caught upon the surface film, 
but find another, and indeed a more constant source, in the organisms 
that dwell below but come up to the surface film. Among these, 
Ostracods and like forms are available as more or less staple food and 
Mesovelia have been observed exploring the sides of floating Typha and 
the tangled mats of alge for such Crustacea which they spear from the 
surface of the water. 
The tiny nymphs feed upon more gentle organisms in the water, 
as there are few upon the surface that they are able to overcome. When 
offered springtails, as suggested by Butler, disaster often followed, and 
the writer lost many good rearings before he learned the inadvisability 
of offering such food. The hungry little creatures would attack them, 
only to be turned topsy-turvy upon the water, even by comparatively 
small springtails. Plant lice afforded less risk of this kind and gave 
better results. They were used as the food supply in the isolation rear- 
ings where a study of molts was made. But in an aquarium 12 inches 
in diameter, the water of which contained algz and floating sedge stems 
amongst which dwelt an abundant population of Entomostracans, the 
little bugs were reared through their complete cycle without other re- 
source than that afforded by the waters and the weaker of their own 
kind. 
Mating. In mating the male mounts the female, clasps his fore legs 
around her mesothorax in front of her middle legs, rests his middle legs 
upon the water film or other supporting surface, and holds the hind legs 
poised in the air. The copulatory organ of the male is long and curves 
around the side of the tip of the female’s body to come into contact 
with the genital opening. Contact lasts from a few seconds to one 
minute or longer. Upon withdrawal the copulatory organ is seen to be 
a slender white tube of astonishing length. 
Oviposition. Since Mesovelia hides and protects its eggs by burying 
them in the tissues of certain plants that are associated with shores 
and shallow waters, the female possesses an ovipositor adapted to this 
purpose. If the female be examined in lateral view, the abdomen is 
seen to be laterally compressed at its caudal end in such a manner as 
to provide a sheath or groove for the ovipositor. A dissecting needle 
inserted near the distal and caudal end of this fissure can be used to 
pry out and bring to view a shiny brown chitinized organ which may be 
turned down into a position approximately at right angles to the body, 
for its attachment is at the basal end of the sheath. In this position 
it is seen to be curved so that the tip is directed slightly forward. The 
general shape, viewed from the front, is roughly spear-shaped and the 
parts arranged in such a way that the front surface is concave, form- 
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