4 
Introduction. By Dr. A. Seitz. 
surpass a certain height without becoming a hindrance, and the way in which many Geometrid larvae extend 
their bodies stiffly into the air when in repose, without any hold or only with the support of a very thin 
silky thread, probably limits the growth and weight of the larva. 
As to the way of feeding, we meet with the greatest variability among the Geometridae of all countries. 
Some species, such as the African Coenina dentaria Swh., are condemned to monophagy by the complete 
adaptation of their shape to the food-plant. Acacia nilotica. Whilst others, as particularly species of Eupithecia 
and their allies, are able to alter their exterior when they change their food-plant, their colouring adapting 
itself to each different food-plant. Other species again may feed on different kinds of trees, though they 
are never found on herbs, whereas others exhibit an extreme polyphagy among herbs, without ever rising to 
shrubs or trees. By preferring dried plants, Sterrha bonitata, which we mentioned above for its small size, be¬ 
comes destructive to herbaria, and the more so since it breeds rapidly and most exactly selects the plants it 
wants to attack, preferably destroying certain species, particularly those having been brought into the herbaria 
from districts of America where the Sterrha could not be discovered before. 
It is obvious that the Geometrid larvae, owing to their mode of moving, can neither mine nor burrow 
into wood or fruit. Many species, however, are fond of blossoms and others attack the buds that are about 
to develop. They are therefore compelled to pass their whole larval period in the usually short flowering 
season of their food-plant, and as this feeding-period of the larvae is so very short, these species are unable to 
attain a considerable size. This is the case in most of the American Eupithecia, at least 150 of which occur in 
the United States alone. 
The development of a functionary proboscis in most of the American Geometridae proves that they 
take up food and, above all, liquid. The body being generally slim would — especially in the hot districts of 
the neotropical region — quickly dry out, if it were not constantly supplied with liquid. It has been already 
stated in another place, in what excessive way some tropical Geometridae, such as the Panther odes, continually 
rinse their intestines with water. 
The flying-season of the Geometridae is relatively long. In the temperate zones of America many 
species fly in two generations often overlapping each other. In this case the pupa mostly hibernates. Thus 
we may meet with the imagines of some more common Geometridae in the United States, such as Semiothisa 
aemulataria Walk., throughout the summer from March until the latter part of autumn. The hibernal Geo¬ 
metrid Alsophila pometaria Harr, may be found as imago every day from autumn until spring, and the more 
we approach the tropics, the longer lasts the flying-season of most of the Geometridae, so that the swarming 
period of many South-American species extends over the whole year. Thus for instance the common species, 
such as Sericoptera mahometaria H.-Schdff. or Nepheloleuca politia Cr. may be met with in some districts 
every evening throughout the year. 
Most of the lepidoptera of the Geometrid family come into the collector’s hands by the light-capture 
which is now being carried on more methodically also in the American Tropics. Nearly all the species are 
greedy for light, flying around the collective-lamp or street-lamp until they settle down on the lamp-post or on 
the ground; it is apparently only in the evenings with exceptional meteorological conditions that they are 
able to part from the light and fly off again. This lighting in the tropical towns means destruction to immense 
numbers of Geometridae. As long as they fly around the light, the bats work havoc mercilessly among them, 
and on settling for repose at the foot of the lantern they fall victims to the toads (Bufo marinus). When the 
swarming season is drawing to an end, the ground below the lamps is often densely covered with Geometridae, 
and then crowds of toads come out from their hiding-places, licking up the lepidoptera which lie about so very 
thoroughly that the birds flying to these places in the morning can scarcely pick up a single specimen that 
has been left over. I often saw numbers of Geometridae still lying in front of my house at midnight, not one 
of which was to be discovered in the morning. 
All 6 of the subfamilies forming the Geometrid family occur in the American fauna. It is to be noted 
that two groups hitherto numbered among the Oenochrominae might be better classed as subfamilies: these are 
the Ametridicae and Hedylicae, both of which are entirely confined to the neotropical region. 
