Studies on Norwegian Aphids - Norsk entomologisk forening

Bombus jonellus (Kirby) (Hym., Apidae)
has Two Generations in a Season
OVE MEIDELL t
Abstract: MEIDELL, O. 1968. Bombus jonellus (Kirby) (Hym., Apidae) ha;; two generation;; in a sea;;on.
Norsk ent. Tidsskr. 14, 31-32.
It is ;;tated that B.jonellus (Kirby) produce;; two generations in a ;;ea;;on. The frequency of worker;; reache;;
one maximum during June and another in the la;;t half of August. A young queen from a colony (1;;t
generation) kept under ob;;ervation mated on 15 July. She established a colony (2nd generation) from
which the fir;;t worker emerged on 15 Augu;;t.
It is generally known that bumble bees produce
one generation in the sense of queen
broods in a season. The hibernating queens
establish their individual nests, produce a varying
number of worker broods succeeded by
sexual brood. Soon after the males and the
young queens have emerged the cycle is completed
and the colony breaks up. The mated
queens hibernate and establish colonies of their
own in the following spring.
The claim that a bumble bee produces two
generations in a season, moreover in Norway,
is striking and may justify the delayed publication
of the following. It is taken from the notes
of the late O. Meidell, which are kept at the
Zoological Museum, University of Bergen.
A;;trid Laken
Zoc1ogical Museum, University of Bergen
In a survey of the bees around Bremen, Germany,
Alfken (1914) briefly suggests that Bornbus
jonellus (Kirby) may produce two generations
in a season based on a possible maximum
flight intensity of workers observed early in
June and another in September.
This theory has stimulated a study of B. jnne/lus
in Rogaland county, situated in the
southwestern part of Norway. The frequency
distribution of the exsisting material of 'l''l',
99 and 66 throughout the season may be summarized
as follows: An almost equal number
of queens occurs in the field during the first
three weeks of May and is then reduced to a
minimum during June. The workers appear
about 20 May, increase rapidly in number and
reach a maximum during June. A rapid decline
occurs in the first week of July and then
the number of workers is slowly reduced to a
minimum at the end of this month. The first
males are recorded at the beginning of June,
reach their greatest number at the end of the
month and are numerous in the first week of
July as well, at a time when some young
queens appear. The number of those queens
in the fields is constantly low because they prefer
to stay in the nest or swarm at the top of
trees. Near the end of July only a few workers
are observed. Males and young queens
have disappeared except for rare single records.
Nests kept under observation agree in the
main with the life cycle outlined above: The
colonies are established towards the end of
April. The first brood, hatching in the last half
of May, contains six to ten workers. One or
two males may emerge about the same time
as the second worker brood in the first half
of June. The colony reaches its maximum number
of workers about midsummer, and at that
time most of the males and the first batch of
young queens are emerging. The remaining