Development, adult size and fecundity of Aphidius sonchi reared in two instars of its aphid host, Hyperomyzus lactucae

Abstract

Development, adult size and fecundity of the aphid parasite, Aphidius sonchi Marshall (Hymenoptera: Aphidiidae), which began their development in the first and third instar nymphs of Hyperomyzus lactucae (L.) (Homoptera: Aphididae), were studied in the laboratory. Survival and development times were almost identical in the two host instars. However, adult parasites reared in the first instar hosts were smaller and had fewer eggs at emergence than those reared from the third instar. Further analysis showed that the size of an adult parasite, irrespective of host stage at reception of the parasite egg, was largely determined by the size of the host when the parasite was in its destructive feeding phase. Furthermore, within parasites reared from each of the two host instars, the earlier emerging individuals were larger and contained more eggs on emergence. However, the relationships between size, development time and fecundity in the parasites differed significantly between cohorts reared from the two host instars. These results indicate that (1) the suitability of the aphid to the development of the parasite varies as the aphid develops, and (2) several aspects of the parasite biology must be studied to show the relative suitability of the aphids of a given instar. RÉSUMÉ Développement, fécondité et taille des adultes d'Aphidius sonchi élevés dans deux stades du puceron Hyperomyzus lactucae L'étude a porté sur le développement, la fécondité et la taille des adultes d'A. sonchi Marshall (Hym: Aphidiidae) qui commence son développement dans le ler et le 3ème stades larvaires d'H. lactucae (Homopt: Aphididae). La survie et la durée de développement sont presque identiques dans les hôtes des deux stades. Cependant les adultes élevés dans le ler stade de l'hôte étaient plus petits et avaient moins d'oeufs à l'émergence que ceux élevés dans le 3ème stade. Des observations ultérieures ont montré que la taille de l'adulte, indépendamment du stade de l'hôte au moment de la réception de l'oeuf, était fortement déterminée par la taille de l'hôte au moment où la larve du parasite était dans sa phase alimentaire destructrice. De plus, parmi les parasites élevés à partir des hôtes de chacun des deux stades, les premiers émergés étaient plus gros et contenaient plus d'oeufs. Cependant la relation entre taille, durée de développement et fécondité des parasites différait significativement suivant les cohortes élevées à partir des hôtes des deux stades. Ces résultats indiquent (1) que l'adéquation du puceron au développement du parasite change pendant que le puceron se développe et (2) que différents aspects de la biologie du parasite doivent être étudiés pour montrer l'adéquation relative des pucerons d'un stade donné.

Attack behavior and host size selection by Diglyphus begini on Liriomyza trifolii in chrysanthemum

“…Host-size selection may serve many functions: certain stages may not be susceptible to parasite attack, host defense systems may be found in various host age classes, (van Alphen & Vet, 1986), or larger hosts may produce larger, more fecund parasites (Liu etal., 1984;Liu, 1985).…”

Diversidade e tamanho de himenópteros parasitóides de Brevicoryne brassicae L. e Aphis nerii Boyer de Fonscolombe (Hemiptera: Aphididae)

“…Isto ocorre porque, mesmo após a oviposição dos parasitóides, os pulgões podem sobreviver e continuar seu desenvolvimento por certo tempo (Shu-Sheng 1985). Hospedeiros parasitados a partir do terceiro ínstar são, inclusive, capazes de se tornar adultos, antes de adquirirem o aspecto de múmia .…”

Flexible Larval Growth Allows Use of a Range of Host Sizes by a Parasitoid Wasp

“…Variation in adult size can influence parasitoid reproductive success by increasing their longevity, fecundity, and searching efficiency (Sandlan 1979, Vinson and lwantsch 1980a, Bellows 1985. In contrast to idiobionts, koinobiont parasitoids (Haeselbarth 1979, Askew andShaw 1986) attack hosts that continue to feed and grow during some stages of parasitism (Vinson and Barras 1970, Jones and Lewis 1971, Smilowitz and lwantsch 1973, Beckage and Riddiford 1978, Cloutier and Mackauer 1979, 1980, Liu Shu-Sheng 1985, Mackauer 1986, Sequeira and Mackauer 1992a. The evolution of the koinobiont life history from the idiobiont habit is discussed by Gauld (1988).…”

“…The potential for host growth during the course of the interaction is dependent upon three parameters that may vary both within and between host-parasitoid associations. First, the host's feeding rate and the nutritional content of the food medium determine its potential for growth, which has corresponding effects upon the development of the parasitoid larva (Guillot and Vinson 1973, Zohdy and Zohdy 1976, Beckage and Riddiford 1983, Liu Shu-Sheng 1985, Mackauer 1986, Slansky 1986). Second, some parasitoids that attack a range of host instars display varying degrees of developmental plasticity, spending variable and often extended periods as first-instar larvae when developing in small or unsuitable hosts (Clausen 1962, Doutt 1964, Corbet 1968, Smilowitz and Iwantsch 1973, Sato 1980, Sato et al 1986).…”