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Tachinid Parasites Attacking Melolonthid Larvae in New Zealand.
[Read before Nelson Philosophical Society, May 21, 1945; received by the Editor, May 25, 1945; issued separately, December, 1945.]
Introduction.
During the summer of 1943–44, while making surveys of parts of the Nelson province to obtain data regarding the distribution of melolonthid larvae, the writer encountered numerous specimens containing tachinid larvae. As far as possible in such cases, half the material was reared, while the other half was preserved in the larval stage. In this way, a fair representation of both larval and adult stages of the tachinids was available for study.
The most interesting observation made in relation to the occurrence of these parasites was that none of them appeared to attack the commonest of all New Zealand melolonthids, Odontria zealandica White. On further investigating the facts, it was found that none of the parasitised material was collected in open pasture country, and most of it occurred in tussock just on the bush-line, or in dense forest. Parasitism reached its peak at an elevation of over 4,000 feet in the Upper Travers Valley, where the commonest parasitised species was Pyronota inconstans Brookes, and the parasite was Avibrissina brevipalpis Malloch. Larvae of Pyronota sp. were also heavily parasitised by Avibrissina on the Whangamoa Saddle. At Lake Rotoiti, in the Upper Travers Valley, on the Whangamoa Saddle, and in the Upper Maitai Valley, undetermined species of Odontria were found parasitised by Neotachina laticornis Malloch, which species was found itself parasitised by a proctotrypoid wasp in the Upper Travers Valley. At the mouth of the Travers River at Lake Rotoiti, a larva of Chlorochiton sp. was found containing three larvae of Procissio cana Hutton. In the following account, the fully-fed larvae of the three tachinids are described.
Descriptions of the Tachinid Larvae.
1. Procissio cana Hutton. (Figs. 1–7.)
Somewhat stoutly fusiform. Blunt posteriorly, more tapered anteriorly. Colour creamy-white. Pleural ridges fairly prominent, and the ventral area below the ridges marked by faint longitudinal striae. Dermal armour profuse, present on all segments, but confined to the dorsal surface on the last two. Dorsally only the central third of each segment free of spinules. The spinules (Figs. 4 and 5) which are arranged in short over-lapping rows, are usually curved, fairly strongly chitinised (especially on posterior spiracular area), and evenly tapering from the base to the tip, which may be simple or
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bifid. Spiracles fairly conspicuous. The anterior pair (Fig. 3) each consist of 10 incompletely septate oval slits (sld.) opening on digitate processes (dp.), which unite to form the spiracular sac (sps.). The posterior pair (Figs. 2 and 6) are on heavily chitinised papillae, and consist of three rather long, elongate, narrow parallel sided, somewhat sinuate slits, each divided by numerous partial or complete septa. A definite spiracular button (bu.) is present. In the bucco-pharyngeal skeleton (Fig. 7) the theca (th.) has two blunt projections (P.) antero-dorsally. The acute dorsal cornu (dc.) does not overlap the ventral one (vc.). The hypopharyngeal arch (ha.) and parastomal sclerite (ps.) are distinctly separated from the theca. The parastomal sclerite is anteriorly very much narrowed to its articulation with the oral hooks (oh.).
Length: 12 mm.
Breadth: 4.5 mm.
Three specimens found in a larva of Chlorochiton sp. at Lake Rotoiti, 10/10/43.
2. Neotachina laticornis Malloch. (Figs. 8–11.)
Larva very similar on casual observation, to that of Procissio cana. The main differences are in the somewhat reduced dermal armour, the lack of definite pleural ridges, and the lack of striae on the ventral surface. The dermal armour is very similar to that of Procissio, both in distribution, which is, however, somewhat reduced, and in the form of the spinules, except that bifid types do not appear to exist in this species and spinules are less heavily chitinised. The anterior spiracles (Fig. 9) each consist of five slits (sl.) opening from digitate processes (dp.) of the spiracular sac (sps.). Each slit is strongly septate, and fairly large. The posterior spiracles (Fig. 10) are very heavily chitinised with three almost straight slits, one median and two lateral and converging posteriorly. Septa very indefinite. Bucco-pharyngeal skeleton (Fig. 11) differs from the above species, in that the dorsal cornu (dc.) overlaps the ventral one (vc.), whose dorsal portion forms a large rounded plate. The ventral cornu is divided postero-longitudinally by a lightly chitinised area. The hypopharyngeal arch (ha.) and parastomal sclerite (ps.) are distinctly separated from the theca, but are not markedly narrowed anteriorly, and have a broad articulation with the oral hooks.
Length: 10 mm.
Breadth: 3.5 mm.
Several specimens in Odontria sp. larvae at Lake Rotoiti, Upper Travers Valley (hyperparasitised by proctotrypoid), and Whangamoa Saddle, during November and December, 1943.
3. Avibrissina brevipalpis Malloch. (Figs. 12–16.)
Larva less tapered anteriorly than the previous two species, with dermal armour very much reduced, and the spiracles not conspicuous. Pleural ridges absent.
Dermal armour on each segment but the posterior one, as two or three weakly-developed rows of spinules on the dorsal surface. The second and third segments have a few ventral spinules. The anterior
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Fig. 1.—Procissio cana Hutton, entire larva.
Fig. 2.—Procissio cana Hutton, posterior spiracular area.
Fig. 3.—Procissio cana Hutton, anterior spiracle.
Fig. 4.—Procissio cana Hutton, dermal spinules.
Fig. 5.—Procissio cana Hutton, oral area.
Fig. 6.—Procissio cana Hutton, posterior spiracle.
Fig. 7.—Procissio cana Hutton, bucco-pharyngeal skeleton.
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Fig. 8.—Neotachina laticornis Mall., larva in host.
Fig. 9.—Neotachina laticornis Mall., anterior spiracle.
Fig. 10.—Neotachina laticornis Mall., posterior spiracle.
Fig. 11.—Neotachina laticornis Mall., bucco-pharyngeal skeleton.
Fig. 12.—Avibrissina brevipalpis Mall., entire larva.
Fig. 13.—Avibrissina brevipalpis Mall., anterior spiracle.
Fig. 14.—Avibrissina brevipalpis Mall., dermal spinules.
Fig. 15.—Avibrissina brevipalpis Mall., posterior spiracle.
Fig. 16.—Avibrissina brevipalpis Mall., bucco-pharyngeal skeleton.
(Key to letters on Plate 24.)
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spiracles (Fig. 13) are glove-like, with four short, digitate processes, each terminated by a minute slit. The entire organ is membranous. The posterior spiracles (Fig. 15) have four short, broad slits, non-septate, but granular. A distinct button (bu.) is present on the spiracular plate. The theca is similar to that of Neotachina in the relationships of its cornua, and in the presence of a lightly-chitinised area below the ventral cornu. In the present species, however, this lightly-chitinised area is much shorter than in Neotachina, and the dorsal cornu is small. The hypopharyngeal arch (ha.) and parastomal sclerites (ps.) are not visibly separated from the theca. The oral hooks are slender and not so acute as in either of the preceding species. They do not bear marked dorsal plates such as are usually present.
Length: 8 mm.
Breadth: 2.8 mm.
Found fairly plentifully in Pyronota sp. larvae on the Whangamoa saddle, and in Pyronota inconstans larvae in the Upper Travers Valley, during November and December, 1943.
Acknowledgment.
The writer is indebted to Mr. E. S. Gourlay, of the Cawthron Institute, for assistance in the identification of the tachinid flies.
References.
Malloch, J. R., 1926–1932. Revision of the Calyptrate Diptera of New Zealand (Parts I–VII). Proc. Cant. Mus., vol. 111, nos. 1–7.
— 1938. Revision of the Calyptrate Diptera of New Zealand (Parts VIII and X). Trans. Roy. Soc. N.Z., vol. 68, Part 2, pp. 161–258.
Miller, D., 1933. The Bucco-pharyngeal Mechanism of a Blow-fly (Calliphora quadrimaculata, Swed.). Parasitology, vol. 24, no. 4, p. 491.
— 1939. Blow-flies (Calliphoridae) and their Associates in New Zealand. Cawthron Institute Monographs, No. 2.