Phoresy by Hemisarcoptes (Acari : Hemisarcoptidae) on Chilocorus (Coleoptera : Coccinellidae): influence of subelytral ultrastructure

Authors
Citation
Ma. Houck, Phoresy by Hemisarcoptes (Acari : Hemisarcoptidae) on Chilocorus (Coleoptera : Coccinellidae): influence of subelytral ultrastructure, EXP APPL AC, 23(2), 1999, pp. 97-118
Citations number
43
Categorie Soggetti
Entomology/Pest Control
Journal title
EXPERIMENTAL & APPLIED ACAROLOGY
ISSN journal
01688162 → ACNP
Volume
23
Issue
2
Year of publication
1999
Pages
97 - 118
Database
ISI
SICI code
0168-8162(199902)23:2<97:PBH(:H>2.0.ZU;2-C
Abstract
The non-phoretic stages of mites of the genus Hemisarcoptes are predators o f the family Diaspididae. The heteromorphic deutonymph (hypopus) maintains a stenoxenic relationship with beetles of the genus Chilocorus. The mites a ttach to the subelytral surface of the beetle elytron during transport. The re is variation in mite density among species of Chilocorus. Both Hemisarco ptes and Chilocorus have been applied to biological control programmes arou nd the world. The objective of this study was to determine whether subelytr al ultrastructure (spine density) plays a role in the evolution of symbiosi s between the mite and the beetle. The subelytral surfaces of 19 species of Chilocorus and 16 species of Exochomus were examined. Spine density was de termined for five subelytral zones: the anterior pronotal margin, medial ce ntral region, caudoventral tip, lateral distal margin and epipleural region . Spine density on the subelytral surface of Chilocorus and Exochomus was i nversely correlated with the size of the elytron for all zones except the c audoventral tip. This suggests that an increase in body size resulted in a redistribution of spines and not an addition of spines. The pattern of spin e density in Exochomus and Chilocorus follows a single size-density traject ory. The pattern of subelytral ultrastructure is not strictly consistent wi th either beetle phylogeny or beetle allometry. The absence of spines is no t correlated with either beetle genus or size and species of either Chiloco rus or Exochomus may be devoid of spines in any zone, irrespective of body size. A general difference between species of Chilocorus and Exochomus is t he fact that while spine density in Chilocorus is clinal relative to the si ze gradient, Exochomus is dichotomous and likely to have either many spines or no spines in a particular zone. No species of Chilocorus was completely devoid of spines. Five species of Exochomus had no spines at all, thus mak ing it difficult to interpret the primary function of the subelytral spines in a general way. Within the genus Chilocorus, spine density may play a sy nergistic role in host association. Based on morphological evidence alone, these findings lead to the hypothesis that the species of Chilocorus that w ould be most conducive to biological control application in conjunction wit h Hemisarcoptes would be Chilocorus cacti, Chilocorus distigma, Chilocorus fraternus, Chilocorus orbus, Chilocorus tristis and, to a lesser extent, Ch ilocorus bipustulatus. Exp Appl Acarol 23: 97-118 (C) 1999 Kluwer Academic Publishers.