2l6 



BUIylvETlN THE BUREAU OF FISHERIES. 



American species may possibly eat more Hymenoptera than we are aware. Termites, 

 winged ants, and cicadas are also interesting victims of the odonata which have been 

 recorded in other parts of the world. A dragonfly is reported to have dug a cricket out 

 of the ground and eaten it (Habit of a Dragonfly, editorial notes, Psyche, vol. 5, p. 364), 

 but this is the only instance, so far as known, where odonates have eaten any of the 

 Orthoptera. 



Size of Prey. — Perhaps the food of the damselflies is usually made up of smaller 

 insects than that of the dragonflies, but the size of the prey is not always in proportion 

 to the size of the imago that eats it. i$)schna and Anax, two of our largest dragonflies, 

 are among the most persistent eaters of gnats, midges, and mosquitoes, while one of the 

 favorite foods of the damselfly, Argia mcesta putrida, is a black mayfly almost as large as 

 itself. Like that of the nymphs, the appetite of the imago seems well-nigh insatiable, 

 and no sooner is one insect devoured than another is caught. Stories of the amount 

 eaten by some imago are told by nearly every observer, and the present author would 

 add one more to the list. A male A. m. putrida was given eight black mayflies, one 

 after the other, and he ate every one of them, simply throv/ing away the legs and wings; 

 yet any two of them exceeded in bulk the damselfly's whole body, minus its v/ings and 

 legs. 



Source of Food Supply. — The food is usually captured in greater or less proximity 

 to the water, sometimes being picked off the very surface of the latter. However, the 

 female dragonfly habitually hunts at a greater distance from the water than the male. 

 The females of Plathemis lydia and Perithemis domitia are only rarely seen around the 

 ponds. The females of other species come to the water for the purpose only of laying 

 their eggs, while the males are constantly patrolling the surface of the ponds, as well 

 as the banks in the immediate vicinity. 



Even the males, however, do not obtain all their food near the water. Anax, 

 i^schna, Lihellula pulchella, Tramea, and Bpicordulia make long foraging trips out into 

 the surrounding country and are often found a considerable distance from any body of 

 water. In this way they help to rid the countryside of some of its worst insect pests, 

 especially flies, mosquitoes, gnats, and midges. Such foraging trips are made more 

 often late in the afternoon, toward sunset, and sometimes after. The males, and 

 occasionally a female, of many of the species around the ponds came regularly every 

 evening to the laboratory building and hawked for food. They picked flies off the 

 window screens and the sides of the building, they decimated the hordes of gnats and 

 midges that swarmed in the waning sunshine, and sometimes they ascended high in the 

 air in search of the tiny insects to be found there. Occasionally their hunting was 

 prolonged after sunset, when the insects were particularly numerous. Lihellula luctuosa 

 was the most common of these visitors, but they also included Erythemis, Leucorrhinia, 

 Plathemis, Tramea, Pantala, Anax, ^Eschna, and even Gomphus vastus and G. fraternus. 



Migration of Tenerals. — As soon as possible after emerging the teneral imagos 

 of Lihellula luctuosa fly back onto the prairie, away from the ponds and the river. There 

 they remain in the gullies and among the underbrush until they become ready for 

 pairing and egg laying. A trip of a mile or two up some of the gullies leading back onto 

 the prairie will reveal thousands of these tenerals roosting on the weeds and underbrush. 

 Occasionally an imago of Erythemis, Leucorrhinia, some Gomphus species, or an 

 Enallagma will be found with them. Usually there is no water within reach, but if 



