232 
G. J. Snowball. 
At Crawley there appeared to be two species of Psychoda, a common 
grey one and a rarer wliite. From May to October the larvae, pupae, and 
adults of grey species occur on and in soft, moist, first to third stage cakes, 
especially those in the shade. Botli larvae (PL 1. Fig, 5) and pupae have 
respiratory siphons which are apparently responsible for the high moistiire 
toleration. 
At the time of pupation the larvae come to the surface. The cracks of 
a cake may bo packed tight vith the naked pupae. The total time of life 
history from egg to emergence of adult was 6|- days in September, 1941 (average 
temperature, 13*9° C.). 
Tlie Psychodidae breed in fresher dung than the Sciaridae and con- 
sequently precede them in the succession. In the same stage dung as Psycho- 
did lar^-ae and pupdC, Sepsid and Drosophilid larva occur, followed later by 
Cercyon larvae. 
F. 2. SCIARIDAE. 
# 
Though small flies belonging to Sciara sp. infest dung in the laboratory, 
they are not numerous in the field. The genus Sciara is world-wide, having 
been recorded from Korth and South America, Africa, Southern Asia, and 
Kew Zealand (Skuse, 1889). Tonnoir (1929) estimated the number of de- 
scribed species of Sciara and those in collections in Australia, at 63. 
They can breed in a wide range of organic materials. Fuller (1934). 
records them from carrion. The author has bred them from rotting bark 
and decaying tea leaves. Almost any vegetable detritus which is moist and 
not exposed to intensities of light or strong air currents seems to suffice. The 
comparative rarity of these conditions at Crawley^ accounts for the small 
numbers of Sciara sp. in the field. They breed in late fourth stage dungs- 
more or less sheltered and practically devoid of other insects. 
The larvae (PI, 1, Fig. 6) feed on dung which they comminute into a. 
black powder only held together by moisture. This habit and their large 
numbers render them a great obstacle to the successful rearing of Scarab, 
larvae in the laboratory. There are intlications that they^ vill even attack 
and consume Scarab pupae. 
Pupation occurs in the dung v ithout formation of a pupal cell or cocoon. 
The pupa has no respiratory processes, thougli these do occur in some species- 
of Sciara ((.'sten Sacken, 1862). The j^uipal period \aries froii' two to five 
days. 
Copulation takes place at an early stage, sometimes before the wings of 
the participants are properly iinfolde<l. Tlie ^\hole life cycle from egg to 
adult required 10 to 12 days in June (average temperature, 14-5° C.) and 
July (13*6° C.), 1941. In Denmark, Thomsen and Hammer (1936) estimated 
the length of the life cycle of a species of Sciara to range from 19 to 22 days 
at temperatures of 19° to 22° C. 
The only other Sciarid foiuid at Crawley was a single specimen of ? Zygo- 
netiro sp. bred from cow dung in the laboratory in July. 1941. 
In spite of their short life cycle and fecundity, tlie Sciaridae are reiulered 
of minor importance in the succession in cow dung by tlie frailty of the adults 
and the restricted physiological requirements of the lar\ae. 
F. 3. SCATOPSIDAE. 
Tliese flies are also associated with a variety’’ of decaying materials.- 
Scatopse sp. (? pidicaria) emerged from vessels containing pig, hors(', cow, 
and calf dung in Denmark (Thomsen & Hammer, 1936), and a species occurs- 
on carrion at Canberra. 
