| dc.description.abstract | Development and 'morphology of the
immature stage of Atherigorra eoccata Rondani
were examinedby neans of dissections, linear measurements,
light and scanning electron microscopy of the egg, the larval
ins tars , and the pupa.rium. Cevelqment measurements were of
body lengths and widths and the lengths of the
cepaal.opharynqeal, skeleton. Survival of larvae at different
groNth stages of the sorghum plant WI ae investigated in the
Laboratory and was dependerrton the size of the host plant.
Survival was usually highest whenplants about ~ ,veeks old
were infested, lOtI in, very young plants, and 1000estin plants
nore than 50 days old. Within group:; of' insects hatched from
eggs laid en the sane day, the occurrence of the various larval
instars overlapped.
Study of the seasonal activity showed that adult sorghum
shodt~~es were present throughout the year in varying nurrbers,
and that the variations in nurrbers were lnainly related to rainfall.
'lhere was rapid increase in the numberof adults soon after the
beginning of the rainy season due to increased adult energence
from pupae caused by rainfall. '1here was apparentily a natural
disproporti,on in the nurrber of ferrales; the sex ratio varied
, "
bebleen 1: 1..4 and 1: ~~'9 males to females•
Study of scsre aspects of reproductive biology showed
a .miximumof 346 eggs per female laid during a life span of 62
days. Lcngevity and fecundity of A. soa:ata were found to be
affected mainly by adult diet. Both fecundi,bj and rate of
-xxioviposition
were found to be influenced by mating. Unmated
females had a longer pre-oviposi tion period and irregUlar
o viposi tion, both factors resulting in reduced fecundi,ty ,
si.noe only one egg develops at a tine in an ovariole. Both
protein and sugar were irrportant in the reveloprrent of ovaries.
A verj ICM percentage of females (29.4%)fed an food lacking
in sugar had deval.opedovaries. 'Ihe percentage of ferral.es
with developed ovaries (27.8%)was still lONerwhen flies were
given water alone. vJhenfemale flies were fed on a diet
containing both protein and sugar, 82.9%developed ovaries.
Food containing sugar without protein also enabled a high
percentage of females (75%) to have developed ovaries.
Study of ovi position behavior showed that certain
leaves an the sane plant were preferred for oviposition by the
shoot fly. It was further shosn that preference for the lower
leaf s~ace was dU3to a position effect' rather than leaf ;-
surface characteristics. 'fuere was a ~rked preferenc:e for
sorghum over the other alternative host plants. 'fue flies
appear to restrain ovi position during the periods when sorghum
is unavailable. Hdilever, this restraint'" did rot affect the
efficiency of host plant selection for ovi position by the
flies. Within sorqhum plots there was preference for five leaf
stage plan~ for ovi position. Larvae failed to develc.p
uliy on yotmger plants due to insuficient food supply,
. whereas plants over 50 days old were-rarely laid upon.
'1he distribution of dead hearts within field plots
indicated clustering of larvae, which was a result of the
xxiiattracticn
of plants already damaged to the ovipositing
ferrales. | en |
