82 PRELIMINARY NOTES ON THE ODONATA. 
uncommon for the male to retain his hold upon his mate. In fact, 
copulation and oviposition are often repeated without an intervening 
separation of the pair. The male may be of use in aiding the female 
to evade the sudden dash of an enemy. 
The mode of oviposition differs with the groups: in the 4 grionidae, 
the Aeshnidae and the Cordulegastrinae there is a well developed ovi- 
positor and the eggs are placed in holes cut in the tissues of submerged 
stems (Endophytic oviposition) ; in the Gomphinae and the Libellulidae 
the ovipositor is absent and the eggs are simply dropped or washed 
from the tip of the abdomen as it dabs the surface (Exophytic oviposi- 
tion). 
The hemimetabolic life cycle from egg to egg is thus completed. 
It differs little with the various species except in the period required 
and the habitat. As to the latter, it may be said that there are no 
known marine Odonata and but few inhabit even brackish water. The 
very interesting case of Mecistogaster modestus Selys completing its 
life history in the water collected between the leaf bases of epiphytic 
bromeliads in Costa Rica and Mexico is described in several papers 
by Calvert. Most species inhabit lakes, ponds or streams. 
Enemies of the Dragon-flies. 
Notwithstanding the specialization of the dragon-flies, both nymph 
and imago, for an exclusively predaceous existence, they are preyed 
upon by many enemies. Walker and others state that in certain regions 
there is a great excess of males over females due to the activity of 
frogs. The females are knocked into the water and devoured while 
ovipositing in the stems of plants at the surface or while resting upon 
masses of floating vegetation. Asa few species, especially the damsel- 
flies, descend beneath the water to deposit the eggs, there is every 
chance for the success of this enemy. Teneral and newly merged 
insects are picked up without resistance. 
Birds are undoubtedly responsible for the scarcity of many 
species in the adult state. Walker took Coryphaeschna ingens and 
Epiaeschna heros from the stomach of Chuck-will’s-widow (Antro- 
stomus carolinensis). The WKingbird (Tyrannus tyrannus) is several 
times recorded as feeding upon dragon-flies, and it is quite reasonable 
to suppose that many of the Tyrannidae have this habit. Moore records 
the capture of so large a species as Eptaeschna heros by the Kingbird. 
Several times in the writer's experience families of Kingbirds have 
been found perched upon some tree or fence at the pond-side, the 
young clamoring loudly for the insects taken by the parents. The best 
