THE INSECT ASSOCIATION OF A LOCAL ENVIRONMENTAL COMPLEX. 
47 
This aspect of the question is emphasised in a paper by Hennings * on the relation 
of temperature and moisture to the development of the scolytid beetle Tomicus 
typographies , L., in which he says: “ Dass nicht nur ‘kalte’ sondern ‘nasskalte’ 
Witterung die Entwickelung verlangsamt, hatten schon friiher die Beobachtungen 
im Freien gelehrt ; mein Bestreben ging dahin, den Einfluss der Luftfeuchtigkeit 
ebenso wie den der Temperatur zahlenmassig darzustellen.” In a series of tables he 
shows the relation between temperature and moisture and the time occupied in the 
development of the various stadia of the insect. Perhaps the most exhaustive 
inquiry into the temperature -moisture relations of insects has been made by 
Bachmetjew in two large treatises,! where he states that there is an optimum degree 
of humidity for insect development which differs for different species. Dewitz J has 
also carried out similar experiments with various Lepidoptera and Diptera, notably 
Cochylis ambiguella, (Enophthira pilleriana, Eudemis botrana, Phalera bucephala, 
and Calliphora erythrocephala, in order to determine the maximum temperature 
beyond which the activities of these insects are retarded, and after what period death 
ensues. Both the time and temperature factors were varied with interesting results, 
which depended upon the stage of development of the larvae employed in the tests. 
All of this work is of the utmost significance to economic entomology. It 
is absolutely essential to know the fundamental factors which govern the various 
phases of insect life, and as Sanderson ( loc . cit. p. 64) has remarked : “ Entomology, 
as well as all biological science, must consider its relations to the more exact and 
fundamental sciences of physics and chemistry-, if we are to have exact knowledge 
of the life with which we are dealing.” This author, along with Peairs,§ has lately 
published a more detailed account of his researches in bulletin form. 
There is, however, an objection to indoor experiments in temperature-moisture 
work. It is doubtful in how far one can base one’s conclusions on results obtained 
under laboratory conditions, which are generally radically different from those that 
prevail outside. There are probably other physical factors besides temperature 
and moisture which must be considered, such as light intensity and atmospheric 
gases. To control all of these is by no means easy, but it appears to the author 
that no matter how unimportant any single factor may seem, it must be con- 
sidered as contributing towards the changes which the insect undergoes in its 
progress towards maturity. 
At the Philadelphia meeting of the American Association of Economic 
* Hennings, C., “ Beitrage zur Kenntniss der die Insektenentwickelung beeinflussenden Faktoren,” Biologische 
Centralblatt, 1907, vol. xxvii, p. 327. 
f Bachmetjew, P., (1) Experimented Entomologische Studien: I. Temperature Verhaltnisse lei InseJcten , Leipzig, 
1910, p. 160. (2) Experimentelle Entomologische Studien vom physikalisch-chemischen Standpunkt aus zweiter Band, 
Sophia, 1907, pp. 999 + cviii, pis. 31. 
\ Dewitz, J., “ Physiologische U ntersuchungen auf dem Gebiet der Schadlingsforschung,” Naturwiss. Zeits. f. 
Forst- u. Landwirtschaft, vol. x, pt. 7, pp. 539-549. 
§ Sanderson, E. D., and Peairs, L. M., “ The Relation of Temperature to Insect Life,” Tech. Bull. No. 7, 
New Hampshire Coll. Agric. Exper. St., Durham, N.H., pp. 1-125. 
