Miscophus littoreus

Face of Miscophus littoreus, from Andrade (1960).

For this post's semi-random subject, I drew the crabronid wasp species Miscophus littoreus. This small, mostly black wasp (about five millimetres in length) was described from Morocco by Nuno Freire de Andrade in 1960, with the original description seeming to still be the only source for information about it. Miscophus is a cosmopolitan genus, found on all continents except Australia and Antarctica (though its presence in South America seems marginal). They are characterised by wings with the outer veins reduced or lost so they have at most two submarginal and two discoidal cells, with the second submarginal cell (if present) triangular and petiolate, and mid-coxae that are very closely placed or touching each other along the midline. Miscophus littoreus is one of a group of closely related species within this genus found between north Africa and central Asia with the fuller complement of wing cells, and the features distinguishing it from other species in this group are rather fine: a slightly longer clypeus, a shinier and less punctate mesosoma. The wings are darker shaded towards the ends, and females have a tarsal comb (a series of longer spines along the front edge of the fore tarsus).

Another species of Miscophus, M. ater, from here.

There don't seem to have been any natural history observations made for M. littoreus itself but we can infer that it is probably similar in behaviour to other species of Miscophus. North American Miscophus species dig nests as short burrows in sandy soil, only a few centimetres in length (Bohart & Menke 1976); this is why the females have the tarsal comb. Nests have at most only a few cells each, often only one. The cells are stocked with small spiders, often juveniles (though I suspect the preference for juvenile spiders has more to do with size preference than anything else. The tendency in many Miscophus species to show a reduction in the wing venation is related to a broader tendency in the genus to not be enthusiastic fliers. Most Miscophus females run along the ground rather than fly when hunting prey, and they do the same when carrying prey back to the nest. At most, they may make only short hopping flights. Miscophus individuals on the ground may be mistaken for ants, which they often hang around while foraging, hoping to avoid attention while they search for unsuspecting spiders.

REFERENCES

Andrade, N. F. de. 1960. Palaearctic Miscophus: bicolor group and isolated species (Hymenoptera, Sphecidae). Memórias e Estudos do Museu Zoológico da Universidade de Coimbra 262: 3–136.

Bohart, R. M., & A. S. Menke. 1976. Sphecid Wasps of the World. University of California Press: Berkeley.

Tachytes: Crickets Face Death from Above

A Tachytes species feeding, copyright Stephen Cresswell.

Most people who are not entomologists assume that 'ants', 'bees' and 'wasps' are all mutually exclusive groups of animals. But while bees and ants are distinct from each other, they are both really distinctive subgroups of wasps. It is not difficult to find guides on the interwebs purporting to tell you the differences between a bee and a 'wasp', but many of the points usually cited will not apply to all wasps (usually what is intended is the differences between a bee and a social wasp, which is the type of non-bee, non-ant wasp most likely to make itself known to humans). Some wasps can look very similar to bees indeed.

Diagram of Tachytes ocelli, from here.

Tachytes is a large, cosmopolitan genus of not-quite-bees, including more than 250 species found on all continents except Antarctica. Its members are robust and hairy, and one would have to look very closely to spot the features marking it as a non-bee (such as the point that its hairs, though numerous, are not branched in the manner of a true bee). Tachytes is classified in the Crabronidae, the family of wasps believed to be most closely related to true bees (other crabronids have been featured in earlier posts: here, here and here). Like other crabronids, adult Tachytes are pollinators, feeding on nectar from flowers. Tachytes species can be separated from most other crabronids by the shape of the ocelli. As well as the two large compound eyes with their multiple lenses on either side of the head, many insects have three small single-lens eyes, called the ocelli, on the top of the head (some insects have fewer or no ocelli). When all three ocelli are present, they are arranged in a triangle with one at the front and two at the rear. In Tachytes, the rear ocelli are present but deformed (I presume non-functional, though I don't actually know). They are reduced to a pair of scar-lines shaped roughly like a comma, or the upper part of a question mark without the dot.

Female Tachytes sinensis sinensis with katydid prey, from here.

Like many other wasps, female Tachytes dig burrows in which they they sequester other insects in a paralysed state to provide food for their young (the big change between bees and other wasps was the provision of their larvae with a plant-derived food source such as honey or pollen instead of animal matter). The size of the burrow varies from species to species, but some are quite extensive: the North American species T. praedator digs a burrow with a centimetre-wide entrance about a metre long, with a 70 cm down-shaft followed by a horizontal run of about a foot (Lin 1967). This species digs at night, thus presumably both avoiding the heat of the day and reducing the risk of detection by predators or parasites. The top of the burrow is usually marked by a heap comprised of the removed soil from its digging; in some species, the female will close over the top of the burrow when not actively digging. A series of cells are constructed branching from the end section of the burrow; each of these cells is filled with enough prey to feed one larva, then an egg is laid in the cell and its entrance sealed. Most Tachytes species feed their larvae with Orthoptera such as crickets, grasshoppers or katydids; the exact type preferred differs between species, though I get the impression of a general correlation between the size of the Tachytes species and the size of its preferred prey. At least two exceptional Tachytes species from central Asia (T. ambidens and T. bidens) are known to supply their larvae with small caterpillars rather than orthopterans. The prey is carried by the female held by her legs, with the antennae clasped by the mandibles. Hunting behaviour has been described for two species from North America, T. intermedius and T. mergus, that stock their nest with pygmy mole crickets (Tridactylidae). Females of these species walk along the ground tapping at it with their antennae. When one locates a cricket in its underground burrow, she quickly digs downwards in an attempt to grab the cricket by its head with her mandibles and haul it out. Even if the cricket hears her coming and attempts to flee from its burrow, it may not escape. The wasp moves so quickly that she is often able to grab the cricket in mid-air as it leaps for freedom. These two Tachytes species also differ from others in the genus in that the crickets are sequestered in the nest not fully paralysed: it has been noted that mole crickets recovered from their nests are still quite mobile and even able to jump.

REFERENCES

Bohart, R. M., & A. S. Menke. 1976. Sphecid Wasps of the World: A generic revision. University of California Press.

Lin, C. S. 1967. Nesting behavior of Tachytes (Tachyplena) praedator Fox, with a review of the biology of the genus (Hymenoptera: Sphecidae: Larrinae). American Midland Naturalist 77 (1): 241–245.