242 ENTOMOLOGICAL SOCIETY 



where the beetles were flying. The dew wets the low plants 

 soon after dark, and on account of this the beetles apparently 

 fly earlier, when the plants are still dry. 



Now, if any one had told me that we had in our fauna a 

 Lachnosterna which was flying about in broad daylight in the 

 company of butterflies and bees, I would not have believed it, 

 but at least one such species really exists and was observed 

 by Mr. H . G. Hubbard and myself in the alpine region of the 

 Wasatch Mountains, in Utah. It constitutes, apparently, a new 

 species of the fusca group. The first specimens were seen on 

 June 28th, right within the little mining camp of Alta, situated 

 at the head of the Little Cottonwood Canon, about 9,000' 

 high. At the time of our visit this region was still full of snow, 

 and the Lachnosternas all males were slowly flying close to 

 the ground over those spots where the snow had melted away. 

 A few aspen and willow shrubs and some herbaceous plants had 

 already acquired foliage, but we never saw one of the beetles 

 settle down. This was precisely at half-past six in the after 

 noon ; temperature at 6.35, 52. The sun was still brightly 

 shining, but it was observed that the Lachnosternas flew only 

 in the shadow thrown by the steep mountain side. On June 

 3oth other specimens were seen at the very crest of the range 

 in an altitude of about 11,000'. This crest is here marked by 

 a great snow drift, forming a vertical wall on one side, and in 

 the shadow of this wall, at 6 o'clock p. m., one of the Lachnos 

 ternas was flying about, while a quarter of an hour later several 

 other specimens were seen on the other side of the wall in the 

 shadow of a mountain spur. There was no vegetation in this 

 locality at this season, and the temperature was much lower than 

 at Alta, though we had then no thermometer. The only ex 

 planation I am able to give for this remarkable deviation in 

 habit is that the very low temperature (below freezing point), 

 which sets in in these altitudes soon after sunset, prevents the 

 beetles from flying after dark. 



The time of flight in insects, viz., whether they are diurnal 

 or nocturnal, appears to be of a subordinate importance in the 

 biology of insects ; still when we see that in several Orders the 

 unity in flying habit is maintained even so far as entire families 

 are concerned, it must be conceded that this habit depends on 

 certain peculiarities in the structure of the eye, or other sense 

 organs. In Lepidoptera the unity in flying habit is strictly 

 maintained in the families composing the Rhopalocera and more 

 or less strictly so in some families of the Heterocera, e. g. , the 

 Sesiidse which are strictly diurnal in contradistinction to the 

 Sphingidae which are strictly crepuscular or nocturnal, except 

 ing the genus Macroglossa. The same may be said of entire 

 families in Hymenoptera, Diptera and Orthoptera. In other 



