286 HENRY C. MCCOOK. 



haps kept thera bliiully to the point more exposed to the fire. The 

 fact is a curious and interesting one, but I have not felt at liberty to 

 experiment upon the question which it raises, viz. : the power of this 

 ant to endure extreme lieat. 



Worms, insects, and refuse matter of various kinds furnish the 

 Pennsylvania ants with food. They also feed largely upon the honey- 

 dew of the aphides. In the formicary in the mill there was no trace 

 of anything that could have served for food. The miller had fre- 

 quently seen the ants carrying flies but never grain. I fancied that 

 there might be some communication through the beam with the mill- 

 race in order to tap a water supply. But after considerable examina- 

 tion along the foundation timbers, tracing the beam to the water, and 

 searching diligently everywhere for signs of openings or chippings, 

 I discovered nothing. 



Within the formicary, as it has been described above, were found 

 winged and unwinged insects, grubs or larva:, and cocoons or pupae. 

 The winged insects were the unfertile females and males, and were in 

 considerable and about equal numbers. The females were three-fourths 

 of an inch in length, and one-eighth of an inch across the thorax. 

 The males were seven-sixteenths of an inch long, and one-sixteenth 

 of an inch across the thorax. The unwinged insects were of three 

 distinct forms, the worker major or soldier, one-half of an inch long, 

 the worker minor-large, seven-sixteenths of an inch, and the worker 

 minor-small, one-fourth of an inch in length. The last form, for con- 

 venience, I have called the " dwarf." We note the most apparent 

 distinctions Vatween these five forms. The unfertile female may at 

 once be distinguished by its size and wings. The queen or fertile 

 female was not found, but is doubtless (as is common with the genus), 

 unwinged. There are five abdominal rings, while in the male there 

 are six. There is also a marked difference in the shape of the abdo- 

 men which in the female is sub-cylindrical, and in the male sub-conical, 

 the segments tapering toward the apex, at which appear the (four) 

 thread-like organs distinctive of the sex. There is also a marked 

 difference iu the antennae, which in the female have twelve joints, 

 (I -f- 11), and in the male thirteen, (1 -f- 12); the female antennae 

 are moreover much stouter than the male. Tlie legs of the female 

 are much stouter, and in proportion, shorter than those of the male. 

 There is a very great difference in the size of the head in the two 

 sexes, that of the female being far the greater. The most inter- 

 esting difference, perhaps, is in the structure of the mandible, as al- 

 ready referred to. [8ee Plate IV, with explanation, for these various 

 fornjs.] 



