THE INSECT ASSOCIATION OF A LOCAL ENVIRONMENTAL COMPLEX. 
55 
Although it may he argued that some of the species are not strictly soil insects 
according to the strict usage of the definition, viz. parasitic Hymenoptera (Table X, 
sample l), yet it may just he possible that even they may be identified with the soil 
or with soil-inhabiting forms at some stage of their life-histories. 
The census was carried out during the period extending from October to 
March (1913—14). The author recognises that, for completeness sake, the investi- 
gation should have covered a whole year. This, however, was not possible at the 
time, as the work was interrupted by his departure for America. Still, there is this 
much to be said in favour of a winter census, that the variation in the constitution 
of the subterranean and surface fauna is less at this season than during any other of 
the year. Most soil insects hibernate as larvae and pupae, and so the variation is 
reduced to one of size and development of the individual species. Many larval forms 
do not even vary to this extent, as, with a cessation of feeding and a general 
suspension of all activities consequent on the lowering of temperatures, there is an 
inhibition of growth. Before and after the two months stated, metamorphoses 
progress much more rapidly. From April to September many of the larvae of the 
soil inhabitants have attained the imaginal stage, the adults now frequenting the 
aerial stratum. Therefore it may be justly contended that one is likely to get a 
much better idea of the soil-insect fauna during the winter than at any other season. 
In passing, it may be worth while to draw attention to the fact that many of the 
insect larvae which one commonly encounters in the soil have not as yet been 
adequately described, and some, indeed, not at all. Insufficient knowledge of the 
premature stages of an insect renders accuracy of identity oftentimes extremely 
difficult and uncertain. Where not otherwise possible, the species of the larva or 
pupa can only be determined with exactness by rearing the imago and having this 
identified. Where success did not always attend the rearing of a species, it was at 
least possible to indicate the family and sometimes also the genus. 
Assuredly a wide field exists for the scientist who is willing to undertake 
life-history studies of either predaceous or phytophagous, soil-inhabiting insects. 
Especially is there a lack of information of the facts pertaining to the life- 
histories of species of Empidae, Asilidse, Therevidae, Leptidae, and Tabanidae. As for 
the Stratiomyiidae, the larvae have been classified by Lundbeck,* but the key must 
be used with reserve, as his examination did not exhaust the larvae of all species. 
In the course of our investigations one or two larvae of the family were collected, 
the characters of which would not fit with the descriptions of any in this author’s 
list. The same lack of information applies to the larval forms of most other 
families and orders besides those of Diptera. 
In point of number of species as well as of specimens, the orders most extensively 
represented in our soil census are Coleoptera and Diptera. Of Lepidoptera, there 
were a few surface caterpillars (Noctuidae) which occurred in 4 of the 11 samples 
* Lundbeck, W., Diptera Danica, Copenhagen, 1907, pt. 1, pp. 73-75. 
