HABITS OF THE VARIOUS .SPECIES INVESTIGATED. 5 



II. HABITS OF THE VARIOUS SPECIES INVESTIGATED. 



At first thought it may seem aside from the main problem to discuss such 

 details, but successful work can be done only after learning the habits of 

 these insects. Not being familiar with the subject at the start, the results 

 given here are the outgrowth of four summers of personal experiences in the 

 field, and it is hoped that they may be useful to others who may be led to 

 undertake similar work. A recent paper by MeDermott* is in practical 

 agreement with the experiences herein described. 



The insects were caught by means of a net made of white cheesecloth 

 attached to a light wooden handle about 1.5 meters long. The white cloth is 

 easily seen and avoided by the insects, but it is more easily handled in the dark. 



The habits of the Photuris pennsylvanica are markedly different from the 

 various species of Plwtinus. The Photuris inhabits damp ground along 

 wooded brooks and rivers, and in the daytime it seems to rest in the trees 

 as well as in the grass, from which it does not emerge until after it has become 

 quite dark. It flies high, at great speed, gives a quick flash, and the next 

 moment may be repeating the flash 10 to 20 meters away. The color of 

 the light is a rich bluish-green. Because of the darkness, it usually is 

 impossible to see these insects except when they flash. At times, however, 

 when in flight, a faint glow is visible which is easily followed with the net. 

 Late at night they become more quiet and often may be found, flashing, on 

 grass stems and on golden-rod. When struck to the ground, they run about 

 flashing violently (just the opposite from the Plwtinus) and hence are easily 

 located. Late in the season they seem to rest, without flashing, among the 

 underbrush. Many specimens were caught by beating the brush and taking 

 advantage of their flashing when disturbed and on the ground. 



One compensation for the difficulties in catching the Photuris was in find- 

 ing that they are strong and hardy, not being easily crushed; and that they 

 could be kept for days in large glass beakers (12X18 cm.) containing clean 

 moist sod, the top being covered with cheesecloth. They are carnivorous, 

 eating their dead comrades. In captivity they kill and eat the Plwtinus. 

 The Phot in us pyralis are not so easily kept, but are more plentiful and more 

 easily obtained. In the previous work on the latter, they were caught and 

 the photographs made the same night. In the present work, half the night 

 was spent in catching the Photuris, and usually the photographing of the 

 light was done in a dark room on the following day. 



In the Photuris the light organs of the female are almost as large as those 

 of the male. The females outnumber the males by about 15 to 1, so that 

 one catches but few of the latter. 



The Phot in us pyralis is plentiful everywhere in this locality. It comes 

 out at dusk, when it can be seen and easily caught. It flies low, hovers 

 about the grass, apparently searching for the female. This species is more 

 delicate than the Photuris, is easily injured, and is not so easily kept in 

 captivity. The light organ in the female is very small, and from her habit of 

 remaining in the grass, occasionally flashing, and from the fact that the males 

 outnumber the females by about 1 5 to 1 , the captured specimens of this species 

 were mostly males. The flash is a long fulmination of yellowish light. 



*McDermott, Canadian Entomologist, Nov. 1910. 



