Encapsulation of parasitoid eggs in soft scales (Homoptera: Coccidae)*

Abstract. 1. The Mediterranean black scale Saissetia oleae (Olivier) was the most suitable host for the imported Metaphycus aff. stanleyi Compere and Metaphycus helvolus (Compere) and for the local Metaphycus flavus (Howard). 2. Difficulties were encountered in the mass rearing of the introduced parasitoids, particularly M. aff. stanleyi, on the hemispherical scale Saissetia coffeae (Walker) and on the brown soft scale Coccus hesperidum L., because many of the eggs were encapsulated. 3. Although all the eggs of M.aff.stanleyi were encapsulated shortly after being deposited in S.coffeae, some larvae developed, broke out of the capsule and developed normally. 4. The incidence of parasitized scales containing only encapsulated eggs of any of the three Metaphycus species, increased with the stage of the host.     

Kin recognition in a subsocial treehopper (Hemiptera: Membracidae)

1. Insects exhibiting parental care usually can discriminate between kin and non‐kin individuals, allowing parents to avoid investment in foreign offspring. 2. This study investigated the occurrence of kin recognition in the sap‐feeding insect Alchisme grossa Fairmaire (Membracidae) through bioassays assessing median female distance to nymphs and degree of nymphal aggregation. Each bioassay involved groups consisting of a female and a cohort of kin or non‐kin nymphs (mother and non‐mother treatments, respectively). Furthermore, cuticular non‐volatile compounds were extracted from nymphal cohorts, analysed by gas chromatography‐mass spectrometry and compared between cohorts. 3. In both treatments, nymphs performed a ‘rocking behaviour’ which appears to be correlated with aggregation. Temporal patterns of degree of nymphal aggregation and median female–nymph distance differed between treatments, the former parameter being higher in the mother treatment and the latter being higher in the non‐mother treatment. 4. A total of 40 compounds were found in the extracts. The composition of cuticular non‐volatile compounds differed between nymphal cohorts. 5. These results support the notion that kin recognition in A. grossa is possibly mediated by nymphal rocking behaviour and/or cuticular non‐volatile compounds (i.e. visual and/or chemical cues).     

Factors which influence female crickets' (Acheta domesticus) phonotactic and sexual responsiveness to males

ABSTRACT. Removal of the corpora allata from sexually responsive Acheta domesticus females exhibiting direct, positive phonotaxis resulted in a decline of the directionality of phonotaxis and sexual responsiveness to males for the 3-day testing period. Phonotaxis and sexual responsiveness were restored to the level before allatectomy after topical treatment with JH III. Sexually and phonotactically responsive females, given Precocene I or II showed no change in phonotactic orientation or sexual responsiveness. Females were isolated from males just prior to the imaginal moult. After 3 weeks of isolation (1 2.5 weeks following the imaginal moult) they showed significantly better phonotaxis to the calling song than did females that had been fully exposed to males, or those which had only olfactory exposure to males. There were no significant differences among the groups in their copulatory readiness when placed directly in contact with males. Mating caused a reduction in the phonotaxis of females. Females on the day of imaginal moult responded negatively to the calling song. This negative response disappeared on the day following the imaginal moult and did not re-appear in older females. Topical application of JH III or the synthetic analogue, ZR 515 caused females to become phonotactically positive in response to the calling song on the day of, or the day following the imaginal moult.