154
N. WALOF'F
Flight ie usual in beetles emerging on warm sunny days, but after
conatruction of galleries they cannot be induced to fly. Mating has
never been seen in the galleries, but frequently on broom branch-,
especially in bright sunlight.
Followhg the two main periods of emergence, there are two main
periods of egg laying. The numbers of progeny in a gallery system
varied between 40 and 60 with a maximum of 65. The average fecundity
of 40 experimental pairs kept at 25"C, 70% relative humidity, waa 38.
In this culture some adults lived for more than 70 days. The developmental period of the progeny also lasted 70 days and thus the new
adults overlapped with the survivors of the parent generation.
(b) The life cyole of Hylastimus obacurua is similar to that of P. rhedodactylus. The beetle is also univoltine and overwinters in the larval and
adult stages. Overwintered larvae begin to emerge as adults in late May.
By June galleries contained eggs and larvae and eggs were found up to
the middle of September. There were pupae and new adulta by July and
it seems probable that eggs must have been laid in the early spring by
the overwintered adults.
The most frequent number of progeny in a gallery system was between 30 and 40, with the maximum of 61. There waa usually a pair of
beetles, a male and a female in each gallery, but occasionally there were
two females. It is not known whether the females construct more than
one gallery on broom, ae they are known t a do on clover (Belaohowsky,
1949).
3. Problems aasociated with ampl ling
(a) P. r h e d W y l u s . Brtsically, estimates were made of insect numbers in known numbers of stems and also of the total number of suitable stems in Area 2. The product of these gave absolute estimations of
the population in that area.
However, it was impossible to differentiate between suitable stems
which had been galleried in previous years from the current year's.
Thus all dying stems were removed from Area 2 and replaced with cut
stems with letter references. The number of stems introduced approximately equalled that removed. At intervals of time, stems were cut 10
days before introduction and dried indoors over that period; each stem
wad then placed vertically.
The results of the sampling data are summarised as a life table
(Table XXXVIII) which forms the baais of consideration of the factors
that cause mortality in the population of Phbeopthua.
(b) H. obscurus waa far less abundant than P. rhododactylw and it
R 8s not possible to sample the population quantitatively. Moreover, as
many galleries are made on the main stems a whole living bush had to
N. WALOF'F
Flight ie usual in beetles emerging on warm sunny days, but after
conatruction of galleries they cannot be induced to fly. Mating has
never been seen in the galleries, but frequently on broom branch-,
especially in bright sunlight.
Followhg the two main periods of emergence, there are two main
periods of egg laying. The numbers of progeny in a gallery system
varied between 40 and 60 with a maximum of 65. The average fecundity
of 40 experimental pairs kept at 25"C, 70% relative humidity, waa 38.
In this culture some adults lived for more than 70 days. The developmental period of the progeny also lasted 70 days and thus the new
adults overlapped with the survivors of the parent generation.
(b) The life cyole of Hylastimus obacurua is similar to that of P. rhedodactylus. The beetle is also univoltine and overwinters in the larval and
adult stages. Overwintered larvae begin to emerge as adults in late May.
By June galleries contained eggs and larvae and eggs were found up to
the middle of September. There were pupae and new adulta by July and
it seems probable that eggs must have been laid in the early spring by
the overwintered adults.
The most frequent number of progeny in a gallery system was between 30 and 40, with the maximum of 61. There waa usually a pair of
beetles, a male and a female in each gallery, but occasionally there were
two females. It is not known whether the females construct more than
one gallery on broom, ae they are known t a do on clover (Belaohowsky,
1949).
3. Problems aasociated with ampl ling
(a) P. r h e d W y l u s . Brtsically, estimates were made of insect numbers in known numbers of stems and also of the total number of suitable stems in Area 2. The product of these gave absolute estimations of
the population in that area.
However, it was impossible to differentiate between suitable stems
which had been galleried in previous years from the current year's.
Thus all dying stems were removed from Area 2 and replaced with cut
stems with letter references. The number of stems introduced approximately equalled that removed. At intervals of time, stems were cut 10
days before introduction and dried indoors over that period; each stem
wad then placed vertically.
The results of the sampling data are summarised as a life table
(Table XXXVIII) which forms the baais of consideration of the factors
that cause mortality in the population of Phbeopthua.
(b) H. obscurus waa far less abundant than P. rhododactylw and it
R 8s not possible to sample the population quantitatively. Moreover, as
many galleries are made on the main stems a whole living bush had to