Haemolaelaps

Synonymy of Haemolaelaps and Androlaelaps

Till (1963) made Haemolaelaps Berlese, 1910 a synonym of Androlaelaps Berlese, 1903. However, Till (1963) did not refer to any details of the type species of Haemolaelaps, nor to any detail contained in subsequent papers providing descriptions of marsupialis and other relevant Australian material. It is clear that a broad, unrefined concept of Haemolaelaps was being used, in line with Berlese (1911, 1916, 1918) and Strandtmann (1949). A proposal by Fonesca (1959) to retain Haemolaelaps in a narrow sense, diagnosed by the long pilus dentilis of H. marsupialis, was dismissed since this character was deemed difficult to interpret (see also Strandtmann, 1949; Till, 1963).

The basis for Till’s (1963) synonomy appears to be the broad concept of Haemolaelaps already in use, and a formal recognition that there were not always clear-cut differences between taxa with spur-like ventral setae on leg II and those without. Despite the lack of clear-cut differences in leg II (including the ambiguity of this criterion for species such as Haemolaelaps centrocarpus Berlese), Till (1963) still maintained an informal separation of Androlaelaps into two subgroups comprising an “ Androlaelaps group” with thickened setae on leg II segments, and the large number of remaining species as the “ Haemolaelaps group”. Till’s (1963) recognition of a “ Haemolaelaps group”, albeit an informal one, may be relevant for understanding subsequent nomenclatural inconsistency. Some authors, following Till (1963) explicitly, have called all species Androlaelaps (Costa, 1969; Radovsky, 1985; Farrier & Hennessey, 1993; Halliday, 1998). Others recognised Haemolaelaps as a subgenus within Androlaelaps (Marais & Loots, 1970), while others continued to use Haemolaelaps as a full genus (Furman, 1966; Tipton et al., 1966; Domrow, 1988). However judging by what has been written and the available keys, these differences do not seem to represent disagreement with the concepts of Till (1963) or Strandtmann (1949), and may just be different rankings applied to Till’s (1963) informal subgroups.

Till’s (1963) important decision to make Haemolaelaps a synonym of Androlaelaps is examined below. I do not find any basis to support this action, and Haemolaelaps is here removed from synonomy with Androlaelaps. Hereafter, Haemolaelaps is given the same meaning as the Haemolaelaps marsupialis group (Womersley 1957; Domrow 1988).

Till’s (1963) decision was explicitly based on three characters: “male chelae, female sternal plate and pilus dentilis”, and it was also stated that the leg chaetotaxy of Haemolaelaps and Androlaelaps resembled one another closely. Below I address these four characters in turn:

1. Male chelicerae. Androlaelaps and Haemolaelaps have important and consistent differences in male chelicerae. In Androlaelaps males, the digits lack both teeth and apical hooks. The digits are weakly sclerotised. The spermadactyl is highly variable in length but is always longer than the movable digit and sometimes substantially so, even reaching twice the length of the movable digit. The spermadactyl is straight or only slightly upturned, with the curvature (if present) never abrupt. The fixed digit is shortened and regressed. Importantly, the nature of this shortening leaves the pilus dentilis emerging from the proximal half of the fixed digit, close to the base, never from the apex, nor in the distal half of the digit. In contrast, Haemolaelaps species, male digits may be weakly dentate (Fig. 1) or edentate (Fig. 2) and often with an apical hook. Compared with Androlaelaps, the digits (and spermadactyli) remain relatively well-sclerotised (Womersley, 1957; contra Berlese, 1922). The spermadactyl is only moderately long at most. The spermadactyl turns abruptly upward, with a distinct bend. The fixed digit is shortened and the pilus dentilis emerges from at or near the apex. The pilus dentilis is flagelliform and not inflated.

2. Female sternal shield. Haemolaelaps and Androlaelaps females both have short sternal shields. The affinity of Haemolaelaps was fomerly presented as a stark and simplified choice between the long sternal shields of Gaeolaelaps and Hypoaspis on the one hand, or Androlaelaps on the other (Till, 1963). However, short sternal shields are not only found in Haemolaelaps and Androlaelaps, but in the large majority of symbiotic (hostassociated) Laelapidae, and hence this is a weak character for determining the status of Haemolaelaps.

3. Female pilus dentilis. The length of the pilus dentilis is a useful character to distinguish Haemolaelaps from Androlaelaps, despite rare overlaps. Till (1963) states Androlaelaps has a pilus dentilis that is either inflated or long and slender. Most species of Haemolaelaps have a highly distinctive pilus dentilis that is remarkably long and slender; typically 25–40 long, which is approximately the length of the movable digit. An exception is Haemolaelaps hattenae Domrow which has a short pilus dentilus 14 long. Rarely some species of Androlaelaps also have a long pilus dentilis. For example Androlaelaps cryptomius (Radford) has a flagelliform pilus dentilis which is ca.18 long (personal observations), but this is still shorter than in most Haemolaelaps species.

4. Genu IV chaetotaxy. Despite the stated similarity (Till, 1963) the leg chaetotaxy differs almost completely between Androlaelaps and Haemolaelaps on the important segment, genu IV. Androlaelaps almost invariably has two posterolateral setae on genu IV. However the type species of Haemolaelaps, H. marsupialis, has only a single proximally positioned posterolateral seta (pl2), as do all other members of this group.

It is therefore clear that Till's (1963) decision to synonymise Haemolaelaps and Androlaelaps was based on an early assumption that Haemolaelaps was highly similar and closely related to Androlaelaps; an assumption that was extended even to questionable statements such as these genera having leg chaetotaxy closely resembling one another. The thickened av setae on leg II, once found to be unreliable as genus-level characters, also removed the principal characters with possible diagnostic value recognised up until that time. However the question of the relationship of these genera had been oversimplified because other characters were not being compared. I here present a new diagnosis of the genus Haemolaelaps, based on examination of all the species in the H. marsupialis group, and find many characters that can be used to distinguish these two genera (Table 1).