378 SUMMARY OF CURRENT RESEARCHES RELATING TO 



die rapidly if isolated, but the young forms just hatched from the pupa 

 stage can survive for a day or so. After insemination the female leaves 

 the bats and runs rapidly on adjacent objects (on the cage), and deposits 

 a larva which she presses against the substratum. She then returns to 

 her host. In natural conditions the larvae are probably deposited on 

 the Ijranches. After two to sis days a female may liberate another 

 larva. The newly laid larva shows eleven segments and two pairs of 

 stigmata. The pupa hatches in twelve to sixteen days. The repro- 

 ductive or":ans of the imas:o are described. 



'D' 



Chalcid Parasite of Mussel-scale.* — A. D. Imms has made an 

 interesting study of ApIieUnus mytiJdispidis Le Baron, a Chalcid parasite 

 of Lepidosaphes iiJmi L., the commonest of the injurious Coccidaj found 

 in Britain. The parasite passes through two generations in the year, 

 and the adults consist almost entirely of females. Out of over 750 bred 

 specimens, only ten were males. Parthenogenesis occurs, and is 

 probably the usual method of reproduction. The adult insects seldom 

 resort to flight, and have extremely limited powers of migration. They 

 are positively phototropic, but exhibit no marked geotropic reaction. 



In the first generation the adults appear in greatest frequency 

 between the third week in June and the middle of July. The female 

 lays a single egg on the dorsal or ventral surface of the body of the 

 immature host, only the scaly covering of the latter ])eing penetrated. 

 The newly batched larva closely resembles the full-grown stage in form, 

 and during larval life the insect is an ectoparasite of its host. The 

 second generation of adults mostly appears between the middle of 

 August and the first week in September. They parasitize the sexually 

 mature hosts, and the resulting larvse hibernate through the winter, 

 giving rise to the first generation of adults of the following year. 



As the results of the first generation of parasites the affected hosts 

 invariably die. In the case of the second generation of parasites the 

 affected hosts usually deposit a small number of eggs before succumbing. 

 The parasite exercises an inhibitory effect on oviposition, the essential 

 reduction in the number of eggs not being primarily due, as stated by 

 previous observers, to their destruction by the Ajjhelinus larvae. 



Assuming that every 1000 hosts lay on an average 37,200 eggs, the 

 net results of a year's parasitism entails a reduction of about 7 p.c. of 

 eggs laid. The eflficiency of the parasite is therefore far below that of 

 the most effective insecticides. This is primarily due to its very limited 

 powers of migration, its relatively low fecundity, its marked susceptibility 

 to unfavourable climatic conditions, and the fact that the effect of the 

 second annual generation of parasites is only partial and incomplete. 



Ecology of Coccids.t — G. Teodoro discusses the family of Coccidse 

 in their ecological aspects, referring particularly to peculiarities of 

 structure and habit that come to have special practical importance. 

 Such are the following : the chitinous cuticle, the production of wax 

 and the like, the absence of wings on the females, the reduction of 



* Quart. Journ. Micr. Sci., Ixi. (1916) pp. 217-74 (2 pis. and 5 figs), 

 t Redia.xi. (1916) pp. 129-209 (3 pis. and 3 figs.). 



