wasps

On the backs of wasps

In March, I was given two specimens of solitary wasps that were covered with mites. The first was one of several Crossocerus  (Crabronidae) that had overwintered in holes in a wooden chair left outside on the campus of the University of Alberta. I had expected the mites to be phoretic deutonymphal astigmatans, but they weren’t, they were adult female scutacarids (Prostigmata: Scutacaridae). Many scutacarid species have phoretic and non-phoretic morphs. The big anterior tarsal claws you can see (blurrily) on the photo below are typical for phoretomorphs. What wasn’t typical was a pair of strange internal structures that became apparent in well-cleared specimens.

scutacarid from Crossocerus April 2015 E

At first I thought the pair of round things near the female’s genital area were sperm-storage chambers. But when I Googled ‘Crossocerus’ and ‘Scutacaridae’, I found a paper that showed I was only half right – they were sporothecae*, not spermathecae!

scutacarid from Crossocerus April 2015 C

Two big spores tucked into the genital atrium of this female Imparipes.

scutacarid from Crossocerus April 2015 A

Ebermann & Hall (2004) described a new species of scutacarid, Imparipes haeseleri, from several species of wood-associated Hymenoptera. In the genital atrium of these mites, they observed two large round fungal spores, one on each side, looking remarkably similar to the ones in the mites from the rotting chair. I asked Evert Lindquist, an expert on the Heterostigmata (the larger group to which Scutacaridae belongs) if these mites were Imparipes. Yup, they were. Were they I. haeseleri? There is a closely related species known from North America, I. vulgaris, but several setal characters matched haeseleri rather than vulgaris so I decided to go with Imparipes cf. haeseleri.

Why are the female mites carrying spores? No doubt they and their offspring feed on the wood-digesting mycelium produced from the germinated spores. The mites that hop on wasps as they depart from their overwintering chambers take with them the starter culture for their future meals. Dr. Lindquist noted that the spores these mites were carrying looked very similar to the Nigrospora spores known to be carried by a different species of heterostigmatan, Siteroptes reniformis Krantz. In his 1984 paper, Lindquist notes that S. reniformis “not only serve to transport and place spores of Nigrospora in an environment favorable for germination and growth, they also stimulate mycelial growth, apparently by secreting a chemical substance when feeding on the fungus.”

The second wasp was collected from an overwintered artificial nesting block that was supposed to house solitary bees. It was an Ancistrocerus sp. (Vespidae: Eumeninae). Knowing this, it was easy to guess who the mites were, and slide-mounting confirmed it: deutonymphs of a Kennethiella sp. (Astigmata: Winterschmidtiidae).

Winterschmidtiid_001

Like almost all phoretic deutonymphs of Astigmata, these Kennethiella have a terminal sucker plate to adhere to hosts. Unusually, they also have anterior ocelli. Why ocelli are present in only a small number of Astigmata is unclear (at least, it’s unclear to me).

Winterschmidtiid_003

Sucker plate.

Winterschmidtiid ocelli

Pair of ocelli.

The reason I expected the mites to be Kennethiella is because the relationship between them and their host wasps is famous among acarologists. Cowan (1984) unraveled the interactions for one mite-wasp duo.  To quote the abstract: “The mite Kennethiella trisetosa is phoretic on adults of the wasp Ancistrocerus antilope and develops in the nest with immature wasps. Female mites and a large type of male develop oviparously, whereas a small male develops oviparously. Small males kill each other, but are ignored by large males. By mating with females before small males are mature, large males may monopolize fertilization. Larvae of female wasps usually destroy mites within their cells but, as adults, are reinfested when mated by mite-bearing males. Each time a male wasp mates, about half of its mites transfer to the female.”

It’s worth reading the original to appreciate the full intricacies of these intertwined life-cycles.

Ancistrocerus showing Kennethiella mites 16 Aug 2009

A home-grown Ancistrocerus with a load of Kennethiella, from my back yard in Edmonton a few years ago.

*according to Evert Lindquist, they aren’t sporothecae (which are spore-storage sacs) but simply the spores themselves, tucked into corners of the genital atrium. Thanks, Evert!

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A(i)nts

Worker ants are nasty creatures that are always beating up on other animals, possibly because of sexual frustration, or maybe they feel oppressed by their queens and take out their anger on non-socialists. Whatever the reason, their short tempers and vicious weaponry mean that ants are given a wide berth by most smart organisms.  This is probably why so many non-formicid arthropods try to look like ants. Here are two that we’ve collected as by-catch at Chamela.

(1) Pincher wasp (Dryinidae).  At first I thought “scary ant about to sting!”.  Then I thought “mantis pretending to be ant!”. Then “mantispid!”. Then “what the heck is it?”. Googling eventually brought me to the right family on BugGuide. Dryinids are both predators and parasitoids, which is quite unusual, and use their raptorial legs to grab hosts while ovipositing. Biology of this group is discussed here and here.

ant-mimicking dryinid wasp on leaf Calandria Trail Chamela Stn 19 Feb 2014

Dryinid at a distance.

ant-mimicking dryinid wasp Calandria Trail Chamela Stn 19 Feb 2014 A

Dryinid close up. Note cool raptorial forelegs.

(2) Lacebug (Tingidae). At first I thought “Ant carrying a dead ant”. But it was behaving in a non-antly fashion so I took it back to the Chamela collections room and looked at it under a dissecting scope it was clearly a true bug. The fenestrations suggest that it is a lacebug. If it is indeed a tingid, then as far as I can tell this is a sufficiently rare phenomenon as to be unGoogleable. Has anyone else observed lacebugs that look like ants? UPDATE: I sent some of these to Laura Miller (West Virginia Department of Agriculture), a tingid expert, and they are indeed lacebugs. What’s more, they represent a new species of Aepycysta. Thanks, Laura!

tiny ant-like lacebug Tingidae on leaf Calandria Trail Chamela Stn 19 Feb 2014

Tingid at a distance, looking like two ants (at least, that’s what it looks like to me).

tiny ant-like lacebug Tingidae Calandria Trail Chamela Stn 19 Feb 2014 A

Tingid close up. Note laciness.

In addition to these formiciform insects, we have seen a lot of neat salticids that do an excellent job of pretending to be ants.